2022 Vol. 39, No. 7
2022, 39(7): 3029-3043.
doi: 10.13801/j.cnki.fhclxb.20220325.004
Abstract:
Advanced resin matrix composite technology is an important basic support for the design and manufacture of lightweight structural system of aerospace shuttle vehicles. Firstly, the type and properties of advanced resin matrix composites used in foreign aerospace vehicles, the manufacturing technology, application and development of typical lightweight composite structure were described. And then the vehicular composite structures manufacture and application in major countries were introduced, including the composite application of “X Series” vehicles in USA and HOPE-X vehicles in Japan. Finally, the technical development trend of aircraft composite structure was introduced.
Advanced resin matrix composite technology is an important basic support for the design and manufacture of lightweight structural system of aerospace shuttle vehicles. Firstly, the type and properties of advanced resin matrix composites used in foreign aerospace vehicles, the manufacturing technology, application and development of typical lightweight composite structure were described. And then the vehicular composite structures manufacture and application in major countries were introduced, including the composite application of “X Series” vehicles in USA and HOPE-X vehicles in Japan. Finally, the technical development trend of aircraft composite structure was introduced.
2022, 39(7): 3044-3058.
doi: 10.13801/j.cnki.fhclxb.20220228.001
Abstract:
The performance of facesheet/core interface is the key for the composite sandwich structures to exert their mechanical/multifunctional advantages. The melt-reconstruction of thermoplastic resin provides a new choice for the facesheet/core connection of the thermoplastic composite sandwich structure (TPCSS), which can realize continuous and reliable facesheet/core interface without introducing new materials. This article summarizes the fusion bonding methods of thermoplastic composite sandwich structures in recent years. Common configurations and materials are summarized, and the main fusion bonding methods, including hot plate welding, compression molding, continuous hot pressing, facesheet/core co-weaving and additive manufacturing are reviewed and concluded. Based on the research and application status at home and abroad, the future development trend and application prospects of the fusion-bonded thermoplastic composite sandwich structure are prospected.
The performance of facesheet/core interface is the key for the composite sandwich structures to exert their mechanical/multifunctional advantages. The melt-reconstruction of thermoplastic resin provides a new choice for the facesheet/core connection of the thermoplastic composite sandwich structure (TPCSS), which can realize continuous and reliable facesheet/core interface without introducing new materials. This article summarizes the fusion bonding methods of thermoplastic composite sandwich structures in recent years. Common configurations and materials are summarized, and the main fusion bonding methods, including hot plate welding, compression molding, continuous hot pressing, facesheet/core co-weaving and additive manufacturing are reviewed and concluded. Based on the research and application status at home and abroad, the future development trend and application prospects of the fusion-bonded thermoplastic composite sandwich structure are prospected.
2022, 39(7): 3059-3083.
doi: 10.13801/j.cnki.fhclxb.20220321.001
Abstract:
Lignin is the most abundant renewable aromatic resource in nature, its macromolecular structure is composed of three phenylpropane units (guaiacyl, syringyl and p-hydroxyphenyl) that connected mainly by ether and carbon-carbon bonds, featuring natural biological activities, hydrophilcity and hydrophobicity, nano-scale adjustability, flexibility in structural modification and biocompatibility. Recent progress on functional materials of lignin is critically discussed based on its structural properties. Firstly, the chemical composition and distribution of lignin in plant cell walls are summarized to elucidating its structural characteristics. Subsequently, recent achievements and challenges on advanced materials based on direct functional application, structural modification, and carbonization are discussed. Finally, the recent progress of lignin used in other fields is briefly summarized, meanwhile, the main points towards future developments and directions in advanced materials of lignin are also highlighted.
Lignin is the most abundant renewable aromatic resource in nature, its macromolecular structure is composed of three phenylpropane units (guaiacyl, syringyl and p-hydroxyphenyl) that connected mainly by ether and carbon-carbon bonds, featuring natural biological activities, hydrophilcity and hydrophobicity, nano-scale adjustability, flexibility in structural modification and biocompatibility. Recent progress on functional materials of lignin is critically discussed based on its structural properties. Firstly, the chemical composition and distribution of lignin in plant cell walls are summarized to elucidating its structural characteristics. Subsequently, recent achievements and challenges on advanced materials based on direct functional application, structural modification, and carbonization are discussed. Finally, the recent progress of lignin used in other fields is briefly summarized, meanwhile, the main points towards future developments and directions in advanced materials of lignin are also highlighted.
2022, 39(7): 3084-3103.
doi: 10.13801/j.cnki.fhclxb.20220301.001
Abstract:
Gel (hydrogel and aerogel) is a three-dimensional material of porous structures, which has found various applications. Cellulose has been widely studied in designing gel materials since it is inherently biodegradable and biocompatible. Cellulose and its derivatives can usually form a stable system by dissolving or uniformly dispersing in aqueous solution, and then be made into hydrogels via the proper crosslinking. In addition, cellulosic hydrogels can be further transformed into aerogels with supercritical drying or freeze drying. This work herein provides a systematical review of gel materials designed with cellulose and its derivatives. Firstly, a thorough analysis is implemented on the technologies in cellulosic hydrogel preparation and the mechanisms therein. The influence of different drying methods of aerogel on its morphology and structure are discussed. Furthermore, the applications of cellulosic gel in environmental protection, biomedicine, energy storage and other fields are summarized. Finally, the existing issues in this area are pointed out and prospected.
Gel (hydrogel and aerogel) is a three-dimensional material of porous structures, which has found various applications. Cellulose has been widely studied in designing gel materials since it is inherently biodegradable and biocompatible. Cellulose and its derivatives can usually form a stable system by dissolving or uniformly dispersing in aqueous solution, and then be made into hydrogels via the proper crosslinking. In addition, cellulosic hydrogels can be further transformed into aerogels with supercritical drying or freeze drying. This work herein provides a systematical review of gel materials designed with cellulose and its derivatives. Firstly, a thorough analysis is implemented on the technologies in cellulosic hydrogel preparation and the mechanisms therein. The influence of different drying methods of aerogel on its morphology and structure are discussed. Furthermore, the applications of cellulosic gel in environmental protection, biomedicine, energy storage and other fields are summarized. Finally, the existing issues in this area are pointed out and prospected.
2022, 39(7): 3104-3120.
doi: 10.13801/j.cnki.fhclxb.20210919.001
Abstract:
Graphene quantum dots (GQDs) have attracted extensive attention due to their excellent optical properties and biocompatibility. By modification, the conjugated system of surface structure can be changed, and the separation rate of electron hole pair, optical band gap and luminescence characteristics can be adjusted. Furthermore, their applications in biological imaging, chemical sensing and photocatalysis will be broadened. The preparation methods of GQDs including top-down and bottom-up methods are briefly introduced. The doping methods and the effects of different doping elements on GQDs, grafting modification based on surface functional groups and construction of composite materials consisted of GQDs and other semiconductors are reviewed in details. The applications of graphene quantum dots composites in biological imaging, fluorescence sensing, photocatalysis and other related fields are summarized. Finally, the future research directions of graphene quantum dots are prospected from the aspects of preparation methods, mechanism exploration, performance regulation and application effects.
Graphene quantum dots (GQDs) have attracted extensive attention due to their excellent optical properties and biocompatibility. By modification, the conjugated system of surface structure can be changed, and the separation rate of electron hole pair, optical band gap and luminescence characteristics can be adjusted. Furthermore, their applications in biological imaging, chemical sensing and photocatalysis will be broadened. The preparation methods of GQDs including top-down and bottom-up methods are briefly introduced. The doping methods and the effects of different doping elements on GQDs, grafting modification based on surface functional groups and construction of composite materials consisted of GQDs and other semiconductors are reviewed in details. The applications of graphene quantum dots composites in biological imaging, fluorescence sensing, photocatalysis and other related fields are summarized. Finally, the future research directions of graphene quantum dots are prospected from the aspects of preparation methods, mechanism exploration, performance regulation and application effects.
2022, 39(7): 3121-3130.
doi: 10.13801/j.cnki.fhclxb.20220314.001
Abstract:
There are many advantages in cellulose such as extensive sources, recyclability, good biocompatibility, etc. However, it is difficult to be used individually because of poor thermoplastic properties, excessive hydrophilicity and insufficient mechanical strength. The research progress of cellulose modification at home and abroad are discussed and analyzed from plasticization modification, hydrophobic modification and reinforcement modification of cellulose materials, as well as research focus and development direction of cellulose-based materials are prospected in future.
There are many advantages in cellulose such as extensive sources, recyclability, good biocompatibility, etc. However, it is difficult to be used individually because of poor thermoplastic properties, excessive hydrophilicity and insufficient mechanical strength. The research progress of cellulose modification at home and abroad are discussed and analyzed from plasticization modification, hydrophobic modification and reinforcement modification of cellulose materials, as well as research focus and development direction of cellulose-based materials are prospected in future.
2022, 39(7): 3131-3143.
doi: 10.13801/j.cnki.fhclxb.20210906.001
Abstract:
The preparation of thermally conductive pads with high vertical thermal conductivity and low compressive stress relaxation is of great significance for improving the vertical heat dissipation capability of current high-power electronic components. In this paper, based on the ice template method, a bottom-up vertically oriented thermal network is designed to achieve high thermal conductivity. First, we use dopamine-modified hydroxylated boron nitride nanosheets and silver nanoparticles (BNNS@PDA/Ag) as hybrid thermally conductive fillers, cellulose nanofibers (Cellulose nanofiber, CNF) are used to prepare composite, and a semiconductor is applied as refrigeration table for the composite’s directional freezing. The frozen samples are freeze-dried to form an aerogel, and then polydimethylsiloxane (PDMS) is vacuum poured into the aerogel to prepare BNNS@PDA/Ag-PDMS thermal pad with high thermal conductivity and low stress relaxation. The results show that the theoretical relaxation time loss decreases first and then increases with the increase of silver nanoparticles (Ag NPs) content. When the aerogel mass fraction reaches 19.7wt%, the theoretical relaxation time of the thermal pad corresponding to 3wt% Ag NPs content reaches 32204 at 20% deformation, the vertical thermal conductivity of thermal pad is up to 3.23 W/(m·K). The ice template method can be used to prepare the vertical packing thermal network with high orientation, which has a good application prospect in the field of thermally conductive pads.
The preparation of thermally conductive pads with high vertical thermal conductivity and low compressive stress relaxation is of great significance for improving the vertical heat dissipation capability of current high-power electronic components. In this paper, based on the ice template method, a bottom-up vertically oriented thermal network is designed to achieve high thermal conductivity. First, we use dopamine-modified hydroxylated boron nitride nanosheets and silver nanoparticles (BNNS@PDA/Ag) as hybrid thermally conductive fillers, cellulose nanofibers (Cellulose nanofiber, CNF) are used to prepare composite, and a semiconductor is applied as refrigeration table for the composite’s directional freezing. The frozen samples are freeze-dried to form an aerogel, and then polydimethylsiloxane (PDMS) is vacuum poured into the aerogel to prepare BNNS@PDA/Ag-PDMS thermal pad with high thermal conductivity and low stress relaxation. The results show that the theoretical relaxation time loss decreases first and then increases with the increase of silver nanoparticles (Ag NPs) content. When the aerogel mass fraction reaches 19.7wt%, the theoretical relaxation time of the thermal pad corresponding to 3wt% Ag NPs content reaches 32204 at 20% deformation, the vertical thermal conductivity of thermal pad is up to 3.23 W/(m·K). The ice template method can be used to prepare the vertical packing thermal network with high orientation, which has a good application prospect in the field of thermally conductive pads.
2022, 39(7): 3144-3155.
doi: 10.13801/j.cnki.fhclxb.20210820.003
Abstract:
Draping for 2D woven carbon fiber reinforced plastics (CFRPs) influences the quality of final composite parts directly and significantly. The problems of laying reinforced carbon fibers in the manufacturing of 2D woven CFRPs were studied. A material coordinate system, a global coordinate system and a body coordinate system were built. A non-orthogonal constitutive model according to coordinate transformation relation was proposed based on continuum theory. Mechanical properties of 2D woven CFRPs were tested by uni-axial tensile tests for measuring the tensile properties and picture-frame tests for measuring the shear properties. A one-step plies spreading algorithm for 2D woven CFRPs was developed and an independent one-step plies spreading solver was developed. A cover part was spread. The result shows great consistency that the maximum error is only 5.0 mm which is a 1.9% margin of error. The carbon fiber shear angle distributions by calculation are consistent with experimental results and the maximum error is only 4°. The one-step spreading algorithm of 2D woven CFRPs was verified by calculations and experiments.
Draping for 2D woven carbon fiber reinforced plastics (CFRPs) influences the quality of final composite parts directly and significantly. The problems of laying reinforced carbon fibers in the manufacturing of 2D woven CFRPs were studied. A material coordinate system, a global coordinate system and a body coordinate system were built. A non-orthogonal constitutive model according to coordinate transformation relation was proposed based on continuum theory. Mechanical properties of 2D woven CFRPs were tested by uni-axial tensile tests for measuring the tensile properties and picture-frame tests for measuring the shear properties. A one-step plies spreading algorithm for 2D woven CFRPs was developed and an independent one-step plies spreading solver was developed. A cover part was spread. The result shows great consistency that the maximum error is only 5.0 mm which is a 1.9% margin of error. The carbon fiber shear angle distributions by calculation are consistent with experimental results and the maximum error is only 4°. The one-step spreading algorithm of 2D woven CFRPs was verified by calculations and experiments.
2022, 39(7): 3156-3166.
doi: 10.13801/j.cnki.fhclxb.20210916.006
Abstract:
The filling modification and blending modification of polymers were important methods for the high performance of general plastics. Interfacial compatibility was a common problem in polymer modification. How to improve the interfacial compatibility of composites and explore the correlation between interfacial compatibility and Poisson's ratio are still important topics in polymer modification. Ternary monomer graft polypropylene (GPP) was prepared by solid phase method and blended with glass fiber and polypropylene to prepare polypropylene/glass fiber composites. The structure and properties of the composites were characterized by video extensometer, differential scanning calorimetry, scanning electron microscopy, infrared spectroscopy, dynamic rheological test and universal tensile test. The results show that the addition of GPP compatibilizer improve the interfacial strength of polypropylene-glass fiber composites. With the increase of GPP compatibilizer, the storage modulus (G') and loss modulus (G'') are both increasing, and the increase of G' is greater than that of G''. Therefore, the elastic behavior of the composite system is significantly greater than that of the viscous behavior. The mechanical properties of polypropylene-glass fiber composite with 7wt% GPP are the best, which was verified by Cole-Cole curve. The results of infrared spectroscopy and scanning electron microscopy show that the GPP compatibilizer form an interfacial layer with the glass fiber, which improve the interfacial compatibility between the resin and the glass fiber and enhance the stress transfer of the glass fiber in the polypropylene matrix. GPP was used as a modifier to improve the interfacial compatibility of PP-GF composites. As a modifier to improve the interfacial compatibility of PP-GF composites, larger transverse strain and smaller Poisson's ratio are formed during the tensile process, which improve the mechanical properties of the composites.
The filling modification and blending modification of polymers were important methods for the high performance of general plastics. Interfacial compatibility was a common problem in polymer modification. How to improve the interfacial compatibility of composites and explore the correlation between interfacial compatibility and Poisson's ratio are still important topics in polymer modification. Ternary monomer graft polypropylene (GPP) was prepared by solid phase method and blended with glass fiber and polypropylene to prepare polypropylene/glass fiber composites. The structure and properties of the composites were characterized by video extensometer, differential scanning calorimetry, scanning electron microscopy, infrared spectroscopy, dynamic rheological test and universal tensile test. The results show that the addition of GPP compatibilizer improve the interfacial strength of polypropylene-glass fiber composites. With the increase of GPP compatibilizer, the storage modulus (G') and loss modulus (G'') are both increasing, and the increase of G' is greater than that of G''. Therefore, the elastic behavior of the composite system is significantly greater than that of the viscous behavior. The mechanical properties of polypropylene-glass fiber composite with 7wt% GPP are the best, which was verified by Cole-Cole curve. The results of infrared spectroscopy and scanning electron microscopy show that the GPP compatibilizer form an interfacial layer with the glass fiber, which improve the interfacial compatibility between the resin and the glass fiber and enhance the stress transfer of the glass fiber in the polypropylene matrix. GPP was used as a modifier to improve the interfacial compatibility of PP-GF composites. As a modifier to improve the interfacial compatibility of PP-GF composites, larger transverse strain and smaller Poisson's ratio are formed during the tensile process, which improve the mechanical properties of the composites.
2022, 39(7): 3167-3177.
doi: 10.13801/j.cnki.fhclxb.20210914.001
Abstract:
The resin transfer molding (RTM) process was used to prepare the three-dimensional angle interlocking woven layup composites. The influence of the layer thickness on the tensile properties and failure mechanism was emphatically discussed. The results show that the tensile strength increases significantly with the enhancement of the layer thickness. In the case of similar fiber volume content, the layer thickness has little effect on the tensile modulus. In the process of tensile fracture, the break of each layer is not synchronized, and the augment of layer thickness deepens the diversity in failure strain between the individual layers. The failure samples have significant delamination, no obvious cracks appeared in the layer. The warp yarns show obvious brittle fracture and a large amount of resin chips appears in the interlamination. The failure modes mainly include fiber fracture and extraction, interface debonding, matrix cracking and delamination.
The resin transfer molding (RTM) process was used to prepare the three-dimensional angle interlocking woven layup composites. The influence of the layer thickness on the tensile properties and failure mechanism was emphatically discussed. The results show that the tensile strength increases significantly with the enhancement of the layer thickness. In the case of similar fiber volume content, the layer thickness has little effect on the tensile modulus. In the process of tensile fracture, the break of each layer is not synchronized, and the augment of layer thickness deepens the diversity in failure strain between the individual layers. The failure samples have significant delamination, no obvious cracks appeared in the layer. The warp yarns show obvious brittle fracture and a large amount of resin chips appears in the interlamination. The failure modes mainly include fiber fracture and extraction, interface debonding, matrix cracking and delamination.
2022, 39(7): 3178-3190.
doi: 10.13801/j.cnki.fhclxb.20210804.004
Abstract:
Ball-milling the mixture of black phosphorous (BP) and zinc hydroxyl stannate (ZHS) was carried out to prepare ZHS-BP nanocomposite, which was then introduced into polypropylene (PP) matrix as flame retardant via melt blending. The thermal stability, combustion and mechanical properties of the PP based composites were investigated. Results show that the addition of BP and ZHS could increase the carbon residue of PP, and only 2wt% BP increases the limiting oxygen index (LOI) of the BP/PP composite from 19.7% (for pure PP) to 23.8%. Moreover, BP can effectively reduce the peak heat release rate (PHRR) and total heat release (THR) of BP/PP composite, the values of which are decreased by 32.52% and 17.80% respectively compared with that of pure PP. However, the release of toxic gases from PP combustion is increased obviously as BP is added, ZHS was then introduced as the assistant agent to suppress the smoke release. As a result, the average specific extinction area (av-SEA) and CO emission of ZHS-BP/PP are decreased by 15.42% and 29.76% respectively compared with BP/PP. Mechanical properties test shows that merely adding BP or ZHS has negative effect on the mechanical properties of the composites. However, the addition of ZHS-BP nanocomposite effectively improves the mechanical properties. Compared with BP/PP, the tensile strength and breaking tensile ratio of ZHS-BP/PP composites are increased by 12.51% and 4.04%, respectively.
Ball-milling the mixture of black phosphorous (BP) and zinc hydroxyl stannate (ZHS) was carried out to prepare ZHS-BP nanocomposite, which was then introduced into polypropylene (PP) matrix as flame retardant via melt blending. The thermal stability, combustion and mechanical properties of the PP based composites were investigated. Results show that the addition of BP and ZHS could increase the carbon residue of PP, and only 2wt% BP increases the limiting oxygen index (LOI) of the BP/PP composite from 19.7% (for pure PP) to 23.8%. Moreover, BP can effectively reduce the peak heat release rate (PHRR) and total heat release (THR) of BP/PP composite, the values of which are decreased by 32.52% and 17.80% respectively compared with that of pure PP. However, the release of toxic gases from PP combustion is increased obviously as BP is added, ZHS was then introduced as the assistant agent to suppress the smoke release. As a result, the average specific extinction area (av-SEA) and CO emission of ZHS-BP/PP are decreased by 15.42% and 29.76% respectively compared with BP/PP. Mechanical properties test shows that merely adding BP or ZHS has negative effect on the mechanical properties of the composites. However, the addition of ZHS-BP nanocomposite effectively improves the mechanical properties. Compared with BP/PP, the tensile strength and breaking tensile ratio of ZHS-BP/PP composites are increased by 12.51% and 4.04%, respectively.
2022, 39(7): 3191-3201.
doi: 10.13801/j.cnki.fhclxb.20210831.002
Abstract:
Carbon fiber triaxial woven fabric/epoxy resin (TWF/EP) composite was prepared by resin film infusion (RFI) method, in which T300 carbon fiber was reinforced material, and epoxy resin was matrix.Three-point bending test and tensile test were carried out to study the in-plane bending and in-plane tensile properties. Moreover, 3D profilometer was used to observe the damage morphology of sample after tensile test, and damage mechanism was analyzed. The results show that the bending elastic modulus of TWF/EP composites is quasi-isotropic. The porosity of composite and width of the fiber bundle have significant positive correlation with the bending elastic modulus, and have a negative correlation with the tensile modulus. The primary tensile failure patterns of composites may include tows pull-out, tows fracture and staggered failure. The tensile fracture mechanisms are mainly pure shear failure, torsional shear failure and tenso-shear coupling failure. In addition, the strain concentration region occurs at the interlacing point of the yarn during the progressive damage process.
Carbon fiber triaxial woven fabric/epoxy resin (TWF/EP) composite was prepared by resin film infusion (RFI) method, in which T300 carbon fiber was reinforced material, and epoxy resin was matrix.Three-point bending test and tensile test were carried out to study the in-plane bending and in-plane tensile properties. Moreover, 3D profilometer was used to observe the damage morphology of sample after tensile test, and damage mechanism was analyzed. The results show that the bending elastic modulus of TWF/EP composites is quasi-isotropic. The porosity of composite and width of the fiber bundle have significant positive correlation with the bending elastic modulus, and have a negative correlation with the tensile modulus. The primary tensile failure patterns of composites may include tows pull-out, tows fracture and staggered failure. The tensile fracture mechanisms are mainly pure shear failure, torsional shear failure and tenso-shear coupling failure. In addition, the strain concentration region occurs at the interlacing point of the yarn during the progressive damage process.
2022, 39(7): 3202-3211.
doi: 10.13801/j.cnki.fhclxb.20210909.008
Abstract:
Carbon fiber/epoxy matrix composite laminates are widely used in aerospace automobile and other fields. It is inevitable to encounter low-speed impact events (falling of tools during production and use) in use, resulting in potential safety hazards. Delamination damage is the main damage form after low-speed impact, which will seriously affect the strength and service life of composite laminates. In order to improve its impact resistance, the toughness effect of ultra-high molecular weight polyethylene (UHMWPE) short fiber on the low-velocity impact behavior of composite laminates was studied. Both toughness fiber number and position were investigated. The results show that the maximum load and absorbed energy of composite laminates with 6 short fiber layers increase from 3.19 kN to 4.86 kN and 18.27 J to 28.89 J, ultimately increasing by 52.3% and 58.12% than the virgin laminates, respectively. The residual strength (164.73 MPa) of the modified composite laminates with 2 layers is the highest, which is 95% higher than the original laminates. Both impact damage resistance and delamination resistance of the modified composites are improved, while the dent depths after impact decrease. The toughening mechanism is that the surface energy of the fracture surface increases, and the impact pulls out some fibers, resulting in fiber bridging phenomenon. The pulled out fibers will reduce the stress concentration at the front of delamination, increase the resistance of delamination propagation, make the delamination failure consume more energy in the propagation process, and effectively hinder the propagation of crack.
Carbon fiber/epoxy matrix composite laminates are widely used in aerospace automobile and other fields. It is inevitable to encounter low-speed impact events (falling of tools during production and use) in use, resulting in potential safety hazards. Delamination damage is the main damage form after low-speed impact, which will seriously affect the strength and service life of composite laminates. In order to improve its impact resistance, the toughness effect of ultra-high molecular weight polyethylene (UHMWPE) short fiber on the low-velocity impact behavior of composite laminates was studied. Both toughness fiber number and position were investigated. The results show that the maximum load and absorbed energy of composite laminates with 6 short fiber layers increase from 3.19 kN to 4.86 kN and 18.27 J to 28.89 J, ultimately increasing by 52.3% and 58.12% than the virgin laminates, respectively. The residual strength (164.73 MPa) of the modified composite laminates with 2 layers is the highest, which is 95% higher than the original laminates. Both impact damage resistance and delamination resistance of the modified composites are improved, while the dent depths after impact decrease. The toughening mechanism is that the surface energy of the fracture surface increases, and the impact pulls out some fibers, resulting in fiber bridging phenomenon. The pulled out fibers will reduce the stress concentration at the front of delamination, increase the resistance of delamination propagation, make the delamination failure consume more energy in the propagation process, and effectively hinder the propagation of crack.
2022, 39(7): 3212-3223.
doi: 10.13801/j.cnki.fhclxb.20210911.001
Abstract:
The main reason for the aseptic loosening of the implant is the fretting wear between the implant and the bone tissue. A carbon fiber (CF) reinforced polyetheretherketone (PEEK) composite material was prepared by a layered method. Under simulated body temperature of 37℃ and simulated body fluid (SBF) lubrication conditions, the basic mechanical properties and the fretting tribological properties of the section of CF/PEEK composites were explored. By changing the normal load and displacement amplitude, the frictional force(Ft)-displacement (D) curve, the fretting operating condition diagram and the friction coefficient curve were established. And the wear mechanism of the CF/PEEK composite material was explored through a three-dimensional white light interferometer and a scanning electron microscope (SEM). The results show that with the decrease of the normal load and the increase of the displacement amplitude, the fretting changes from partial slip regime and mixed regime to slip regime. The overall friction coefficient curve is relatively stable. The friction coefficient gradually decreases with the increase of normal load and increases with the rise of displacement amplitude. The wear volume increases with load and displacement amplitude increases. In addition, CF/PEEK composites have better fretting properties, and the main wear mechanisms are abrasive wear and fatigue wear. The analysis of the tribological characteristics of composite materials provides a specific theoretical basis for CF/PEEK composite materials to replace metal implants.
The main reason for the aseptic loosening of the implant is the fretting wear between the implant and the bone tissue. A carbon fiber (CF) reinforced polyetheretherketone (PEEK) composite material was prepared by a layered method. Under simulated body temperature of 37℃ and simulated body fluid (SBF) lubrication conditions, the basic mechanical properties and the fretting tribological properties of the section of CF/PEEK composites were explored. By changing the normal load and displacement amplitude, the frictional force(Ft)-displacement (D) curve, the fretting operating condition diagram and the friction coefficient curve were established. And the wear mechanism of the CF/PEEK composite material was explored through a three-dimensional white light interferometer and a scanning electron microscope (SEM). The results show that with the decrease of the normal load and the increase of the displacement amplitude, the fretting changes from partial slip regime and mixed regime to slip regime. The overall friction coefficient curve is relatively stable. The friction coefficient gradually decreases with the increase of normal load and increases with the rise of displacement amplitude. The wear volume increases with load and displacement amplitude increases. In addition, CF/PEEK composites have better fretting properties, and the main wear mechanisms are abrasive wear and fatigue wear. The analysis of the tribological characteristics of composite materials provides a specific theoretical basis for CF/PEEK composite materials to replace metal implants.
2022, 39(7): 3224-3231.
doi: 10.13801/j.cnki.fhclxb.20211018.006
Abstract:
The brittleness of epoxy resin needs toughening to meet the application requirements. Protocatechuic acid epoxy resin (PA-EP) was synthesized from protocatechuic acid (PA) and epichlorohydrin via two-step reaction, and used as special epoxy resin for the modification of bisphenol A epoxy resin. The structure and properties of the PA-EP were characterized by fourier transform infrared spectrometer (FTIR), nuclear magnetic resonance spectroscopy (1HNMR), potentiometric titration and viscosity tester. FTIR, 1HNMR and viscosity analyses indicate that the target product are synthesized with epoxy value of 0.73 eq/100 g and viscosity of 43.2 Pa·s at 25℃. The mechanical properties of PA-EP/E-51 thermosets are better than others when the mass ratio of PA-EP to E-51 is 10%. The tensile strength, flexural strength and impact strength are increased by 37.4%, 17.2% and 82.9%, respectively. The scanning electron microscope (SEM) images of impact section show that PA-EP/E-51 thermosets exhibit ductile fracture characteristics. Dynamic mechanical analysis (DMA) and thermogravimetry (TG) results indicate that the glass transition temperature (Tg) increases from 116.0℃ (neat E-51) to 137.3℃ with 12.5% of PA-EP/E-51. The weight loss 10% and the maximum decomposition rate temperature are decreased slightly while the residue content of 800℃ increases from 5.9% (neat E-51) to 9.8% (12.5% PA-EP/E-51).
The brittleness of epoxy resin needs toughening to meet the application requirements. Protocatechuic acid epoxy resin (PA-EP) was synthesized from protocatechuic acid (PA) and epichlorohydrin via two-step reaction, and used as special epoxy resin for the modification of bisphenol A epoxy resin. The structure and properties of the PA-EP were characterized by fourier transform infrared spectrometer (FTIR), nuclear magnetic resonance spectroscopy (1HNMR), potentiometric titration and viscosity tester. FTIR, 1HNMR and viscosity analyses indicate that the target product are synthesized with epoxy value of 0.73 eq/100 g and viscosity of 43.2 Pa·s at 25℃. The mechanical properties of PA-EP/E-51 thermosets are better than others when the mass ratio of PA-EP to E-51 is 10%. The tensile strength, flexural strength and impact strength are increased by 37.4%, 17.2% and 82.9%, respectively. The scanning electron microscope (SEM) images of impact section show that PA-EP/E-51 thermosets exhibit ductile fracture characteristics. Dynamic mechanical analysis (DMA) and thermogravimetry (TG) results indicate that the glass transition temperature (Tg) increases from 116.0℃ (neat E-51) to 137.3℃ with 12.5% of PA-EP/E-51. The weight loss 10% and the maximum decomposition rate temperature are decreased slightly while the residue content of 800℃ increases from 5.9% (neat E-51) to 9.8% (12.5% PA-EP/E-51).
2022, 39(7): 3232-3241.
doi: 10.13801/j.cnki.fhclxb.20210827.001
Abstract:
Using styrene acrylic emulsion, slag geopolymer and graphite powders as raw materials, a foam composite material with the characterstics of self-leveling, fast film-foeming and soildification, high elasticity, and high heat transfer was prepared by the principle of chemical foaming. This paper studied the influence of the content of hydrogen peroxide, the content of thermally conductive graphite powder and its particle size distribution on the heat transfer performance, material mechanical properties and compression deformation properties of foam composites. The research results show that with the increase of the amount of hydrogen peroxide, the tensile strength, elongation at break, compressive strength and thermal conductivity of the foam composite material decrease, and the elastic recovery rate increases; as the content of thermally conductive graphite powder increasing, the tensile strength first increases and then decreases, the elongation at break decreases, the conpressive strength increases, the elastic recovery rate fluctuates slightly, and thermal conductivity increases. As the average particle size of the thermally conductive graphite powder increasing, the tensile strength decreases and the compressive strength increases, and the thermal conductivity first increases and then drcreases. The particle composition of thermally conductive graphite powder has an important effect on its thermal conductivity. Compared with coares and fine particles, a moderate particle gradation can make it form a more effective heat conduction network to obtain a higher thermal conductivity.
Using styrene acrylic emulsion, slag geopolymer and graphite powders as raw materials, a foam composite material with the characterstics of self-leveling, fast film-foeming and soildification, high elasticity, and high heat transfer was prepared by the principle of chemical foaming. This paper studied the influence of the content of hydrogen peroxide, the content of thermally conductive graphite powder and its particle size distribution on the heat transfer performance, material mechanical properties and compression deformation properties of foam composites. The research results show that with the increase of the amount of hydrogen peroxide, the tensile strength, elongation at break, compressive strength and thermal conductivity of the foam composite material decrease, and the elastic recovery rate increases; as the content of thermally conductive graphite powder increasing, the tensile strength first increases and then decreases, the elongation at break decreases, the conpressive strength increases, the elastic recovery rate fluctuates slightly, and thermal conductivity increases. As the average particle size of the thermally conductive graphite powder increasing, the tensile strength decreases and the compressive strength increases, and the thermal conductivity first increases and then drcreases. The particle composition of thermally conductive graphite powder has an important effect on its thermal conductivity. Compared with coares and fine particles, a moderate particle gradation can make it form a more effective heat conduction network to obtain a higher thermal conductivity.
2022, 39(7): 3242-3250.
doi: 10.13801/j.cnki.fhclxb.20210905.001
Abstract:
Natural organisms exhibit excellent mechanical properties due to hierarchical ordered structure and complex organic/inorganic interface interaction. However, the synthetic materials have proven to be difficult to achieve the synchronous improvement of strength, toughness and elongation at break, by merely mimicking their component and structural. Herein, the hybrid films of montmorillonite-cellulose nanocrystal/poly(vinyl alcohol) (MMT-PCNC/PVA) were prepared by electrostatic self-assembly and solvent evaporation. TEM was used to track the formation process. The results of FTIR spectra show that there are multiple weak interactions such as electrostatic and hydrogen bonds in the composite films. The effect of the proportion of MMT and polyethyleneimine (PEI) modified PCNC on the mechanical properties of the composite films was studied. As a result, it is most obvious when the mass ratio is 1∶1 and 1∶2 of MMT and PCNC can drastically enhance the tensile strength (196% for 1MMT-1PCNC/PVA), elongation at break (175% for 1MMT-2PCNC/PVA), and toughness (900% for 1MMT-2PCNC/PVA), which are superior to the pure PVA film. The multiple types of interactions between nanoscale building blocks improve the efficiency of load transfer and cause crack deflection, which result in a highly energy consumption and excellent mechanical properties (such as strength, toughness).
Natural organisms exhibit excellent mechanical properties due to hierarchical ordered structure and complex organic/inorganic interface interaction. However, the synthetic materials have proven to be difficult to achieve the synchronous improvement of strength, toughness and elongation at break, by merely mimicking their component and structural. Herein, the hybrid films of montmorillonite-cellulose nanocrystal/poly(vinyl alcohol) (MMT-PCNC/PVA) were prepared by electrostatic self-assembly and solvent evaporation. TEM was used to track the formation process. The results of FTIR spectra show that there are multiple weak interactions such as electrostatic and hydrogen bonds in the composite films. The effect of the proportion of MMT and polyethyleneimine (PEI) modified PCNC on the mechanical properties of the composite films was studied. As a result, it is most obvious when the mass ratio is 1∶1 and 1∶2 of MMT and PCNC can drastically enhance the tensile strength (196% for 1MMT-1PCNC/PVA), elongation at break (175% for 1MMT-2PCNC/PVA), and toughness (900% for 1MMT-2PCNC/PVA), which are superior to the pure PVA film. The multiple types of interactions between nanoscale building blocks improve the efficiency of load transfer and cause crack deflection, which result in a highly energy consumption and excellent mechanical properties (such as strength, toughness).
2022, 39(7): 3251-3261.
doi: 10.13801/j.cnki.fhclxb.20211126.001
Abstract:
In order to prepare a high temperature resistant thermoplastic composite material with integrated structure and function, which has excellent mechanical properties and electromagnetic interference shielding effectiveness at the same time, the mechanical properties, electrical conductivity and electromagnetic interference shielding effectiveness (EMI SE) of continuous carbon fiber reinforced polyether ether ketone composites (CF-CNT/PEEK) with different components of carbon nanotubes (CNT) were studied. The mechanical properties, interface morphology and shielding effectiveness of SCF-SCNT/PEEK laminates prepared with CNT modified PEEK sizing agent (SCNT) as conductive fillers were investigated, and the effect of the CNT (ACNT) without surface modification and only activation comparative experiment were compared. The results show that an appropriate amount of CNT will improve the mechanical properties, electrical conductivity and shielding effectiveness of the CF/PEEK laminate. SCNT is easier to uniformly disperse in PEEK than ACNT, and has a better combination with SCF and PEEK. In all samples, the tensile strength of SCF-SCNT/PEEK laminates with only 1wt%SCNT increased by 20.8% to 778 MPa compared with laminates without CNTs. Bending strength is increased by 25.9% to 1684 MPa. The conductivity is increased by 5 times, reaching 0.15 S/cm. The electromagnetic interference shielding efficiency is increased by 69.76%, with an average value of 34.97 dB.
In order to prepare a high temperature resistant thermoplastic composite material with integrated structure and function, which has excellent mechanical properties and electromagnetic interference shielding effectiveness at the same time, the mechanical properties, electrical conductivity and electromagnetic interference shielding effectiveness (EMI SE) of continuous carbon fiber reinforced polyether ether ketone composites (CF-CNT/PEEK) with different components of carbon nanotubes (CNT) were studied. The mechanical properties, interface morphology and shielding effectiveness of SCF-SCNT/PEEK laminates prepared with CNT modified PEEK sizing agent (SCNT) as conductive fillers were investigated, and the effect of the CNT (ACNT) without surface modification and only activation comparative experiment were compared. The results show that an appropriate amount of CNT will improve the mechanical properties, electrical conductivity and shielding effectiveness of the CF/PEEK laminate. SCNT is easier to uniformly disperse in PEEK than ACNT, and has a better combination with SCF and PEEK. In all samples, the tensile strength of SCF-SCNT/PEEK laminates with only 1wt%SCNT increased by 20.8% to 778 MPa compared with laminates without CNTs. Bending strength is increased by 25.9% to 1684 MPa. The conductivity is increased by 5 times, reaching 0.15 S/cm. The electromagnetic interference shielding efficiency is increased by 69.76%, with an average value of 34.97 dB.
2022, 39(7): 3262-3270.
doi: 10.13801/j.cnki.fhclxb.20210906.005
Abstract:
The selective oxidation of cyclohexane to cyclohexanol and cyclohexanone is an important process to synthesis of caprolactam, which is an important raw material in the production of nylon. However, the industrial route suffered from the disadvantages such as harsh reaction conditions and low reactivity, therefore, selective oxidation of cyclohexane under mild conditions attracted great attention. Since photocatalysis has unique advantages in saturated C—H activation and oxidation, in this paper, a series of Bi2O3-TiO2 composite photocatalysts were prepared by hydrothermal method. Their structure, morphology, optical and photoelectrochemical properties were characterized in detail by various techniques such as SEM, XRD, N2 physical absorption and desorption, UV-Vis, photoluminescence spectroscopy, and transient photocurrent response. The photocatalytic performance of pure TiO2, Bi2O3 and Bi2O3-TiO2 composites toward selective oxidation of cyclohexane was compared under the reaction conditions of ambient temperature, 0.1 MPa of oxygen, and 500 W xenon lamp simulating solar light source. The results show that the catalytic activities of hybrid Bi2O3-TiO2 composites are higher than that of pure TiO2. Among them, 9%Bi2O3-TiO2 exhibits the highest activity, the conversion is 13.32%, and the total selectivity (cyclohexanone and cyclohexanol) is 95.5%. The selectivity of cyclohexanone and cyclohexanol is 57.3% and 38.2%, respectively, and the ketone to alcohol ratio is 1.5. The characterization results confirm that the composite catalyst has a wider light absorption frequency range and can effectively promote the separation of photogenerated electrons and holes. In addition, the Bi2O3-TiO2 composites possess higher specific surface area than pure TiO2, which is conducive to increasing the concentration of surface active centers.
The selective oxidation of cyclohexane to cyclohexanol and cyclohexanone is an important process to synthesis of caprolactam, which is an important raw material in the production of nylon. However, the industrial route suffered from the disadvantages such as harsh reaction conditions and low reactivity, therefore, selective oxidation of cyclohexane under mild conditions attracted great attention. Since photocatalysis has unique advantages in saturated C—H activation and oxidation, in this paper, a series of Bi2O3-TiO2 composite photocatalysts were prepared by hydrothermal method. Their structure, morphology, optical and photoelectrochemical properties were characterized in detail by various techniques such as SEM, XRD, N2 physical absorption and desorption, UV-Vis, photoluminescence spectroscopy, and transient photocurrent response. The photocatalytic performance of pure TiO2, Bi2O3 and Bi2O3-TiO2 composites toward selective oxidation of cyclohexane was compared under the reaction conditions of ambient temperature, 0.1 MPa of oxygen, and 500 W xenon lamp simulating solar light source. The results show that the catalytic activities of hybrid Bi2O3-TiO2 composites are higher than that of pure TiO2. Among them, 9%Bi2O3-TiO2 exhibits the highest activity, the conversion is 13.32%, and the total selectivity (cyclohexanone and cyclohexanol) is 95.5%. The selectivity of cyclohexanone and cyclohexanol is 57.3% and 38.2%, respectively, and the ketone to alcohol ratio is 1.5. The characterization results confirm that the composite catalyst has a wider light absorption frequency range and can effectively promote the separation of photogenerated electrons and holes. In addition, the Bi2O3-TiO2 composites possess higher specific surface area than pure TiO2, which is conducive to increasing the concentration of surface active centers.
2022, 39(7): 3271-3280.
doi: 10.13801/j.cnki.fhclxb.20210909.001
Abstract:
With regarding to the solar energy conversion applications, BiOBr demonstrated superior photocatalytic property, while its photothermal property and application need further investigation and exploitation. Firstly, BiOBr nanosheets were prepared by hydrothermal method, and then the BiOBr nanopowders were chemically reduced by sodium borohydride. The characterization results show that, with the concentration of sodium borohydride increased, the dense BiOBr nanosheets initially transform into BiOBr/Bi composite porous nanosheets, and then metallic Bi porous nanosheets. The formation of metallic Bi and porous structure is benefit for improving the light absorption ability and specific surface area. The BiOBr/Bi composite porous nanosheets, which are obtained by reduction using 20 g·L−1 NaBH4 solution, possess the best light absorption ability and specific surface area, and the wetting property is also excellent. It therefore demonstrate the best interfacial photothermal driven water evaporation performance. The water evaporation rate reach to 2.18 kg·m−2·h−1, which is twice that of BiOBr nanosheets.
With regarding to the solar energy conversion applications, BiOBr demonstrated superior photocatalytic property, while its photothermal property and application need further investigation and exploitation. Firstly, BiOBr nanosheets were prepared by hydrothermal method, and then the BiOBr nanopowders were chemically reduced by sodium borohydride. The characterization results show that, with the concentration of sodium borohydride increased, the dense BiOBr nanosheets initially transform into BiOBr/Bi composite porous nanosheets, and then metallic Bi porous nanosheets. The formation of metallic Bi and porous structure is benefit for improving the light absorption ability and specific surface area. The BiOBr/Bi composite porous nanosheets, which are obtained by reduction using 20 g·L−1 NaBH4 solution, possess the best light absorption ability and specific surface area, and the wetting property is also excellent. It therefore demonstrate the best interfacial photothermal driven water evaporation performance. The water evaporation rate reach to 2.18 kg·m−2·h−1, which is twice that of BiOBr nanosheets.
2022, 39(7): 3281-3291.
doi: 10.13801/j.cnki.fhclxb.20211129.001
Abstract:
In purpose of obtaining electrode materials with superior electrochemical properties for supercapacitor, porous carbon nanotubes (PCNTs) were firstly prepared by the carbonization and activation of polypyrrole (PPy) nanotubes. The obtained PCNTs were further modified with 9,10-phenanthrenequinone(PQ) molecules via π-π stacking interaction through one-step solvothermal method. The electrochemical performance of the obtained composites (PQ/PCNTs) with different mass ratios of PQ to PCNTs as the electrode materials for supercapacitors were investigated by cyclic voltammetry (CV), galvonostantic charging-discharging (GCD) and electrochemical impedance spectroscopy (EIS). The experimental results show that the composites with the mass ratio of PQ molecule to PCNTs of 5∶5 achieves the largest specific capacity of 407.7 C∙g−1 at a current density of 1 A∙g−1. The resultant composite also exhibits excellent rate capability (the specific capacity at a current density of 50 A∙g−1 is equal to 307.3 C∙g−1) and cycling stability (capacitance retention of 91.4% after 10,000 cycles at the current density of 10 A∙g−1). Furthermore, a symmetric supercapacitor was assembled with the mass ratio of PQ molecule to PCNTs of 5∶5 as electrode materials to investigate the practical applications of the composites. And the assembled symmetric supercapacitor delivers an energy density as high as 21.5 W∙h∙kg−1 and a power density of 0.8 kW∙kg−1.
In purpose of obtaining electrode materials with superior electrochemical properties for supercapacitor, porous carbon nanotubes (PCNTs) were firstly prepared by the carbonization and activation of polypyrrole (PPy) nanotubes. The obtained PCNTs were further modified with 9,10-phenanthrenequinone(PQ) molecules via π-π stacking interaction through one-step solvothermal method. The electrochemical performance of the obtained composites (PQ/PCNTs) with different mass ratios of PQ to PCNTs as the electrode materials for supercapacitors were investigated by cyclic voltammetry (CV), galvonostantic charging-discharging (GCD) and electrochemical impedance spectroscopy (EIS). The experimental results show that the composites with the mass ratio of PQ molecule to PCNTs of 5∶5 achieves the largest specific capacity of 407.7 C∙g−1 at a current density of 1 A∙g−1. The resultant composite also exhibits excellent rate capability (the specific capacity at a current density of 50 A∙g−1 is equal to 307.3 C∙g−1) and cycling stability (capacitance retention of 91.4% after 10,000 cycles at the current density of 10 A∙g−1). Furthermore, a symmetric supercapacitor was assembled with the mass ratio of PQ molecule to PCNTs of 5∶5 as electrode materials to investigate the practical applications of the composites. And the assembled symmetric supercapacitor delivers an energy density as high as 21.5 W∙h∙kg−1 and a power density of 0.8 kW∙kg−1.
2022, 39(7): 3292-3302.
doi: 10.13801/j.cnki.fhclxb.20210819.008
Abstract:
In order to improve the microwave absorbing properties of single magnetic absorbing material, polylactic acid (PLA) was used as the matrix material, and the magnetic material carbonyl iron powder (CIP) as well as reduced graphene oxide (RGO) were compounded to prepare RGO and CIP/PLA composites. The structure and morphology of the composites were characterized by TG, XRD and other testing methods. Meanwhile, the electromagnetic parameters of the composites were measured by vector network analyzer, and the microwave absorbing properties of different thickness were calculated. The influence of RGO addition on the microwave absorbing properties of RGO and CIP/PLA composites was studied. The results show that when the graphene content is 4wt% and the carbonyl iron powder content is 20wt%, the RGO-CIP/PLA composite has the best absorbing performance. When the absorption thickness is 3 mm, the minimum RL value of −27.25 dB is reached, and at the same time its absorption bandwidth is 2.922 GHz (7.227-10.149 GHz). At the same time, as its absorption thickness increases, the effective absorption bandwidth (RL<−10 dB) can move to a lower frequency band.
In order to improve the microwave absorbing properties of single magnetic absorbing material, polylactic acid (PLA) was used as the matrix material, and the magnetic material carbonyl iron powder (CIP) as well as reduced graphene oxide (RGO) were compounded to prepare RGO and CIP/PLA composites. The structure and morphology of the composites were characterized by TG, XRD and other testing methods. Meanwhile, the electromagnetic parameters of the composites were measured by vector network analyzer, and the microwave absorbing properties of different thickness were calculated. The influence of RGO addition on the microwave absorbing properties of RGO and CIP/PLA composites was studied. The results show that when the graphene content is 4wt% and the carbonyl iron powder content is 20wt%, the RGO-CIP/PLA composite has the best absorbing performance. When the absorption thickness is 3 mm, the minimum RL value of −27.25 dB is reached, and at the same time its absorption bandwidth is 2.922 GHz (7.227-10.149 GHz). At the same time, as its absorption thickness increases, the effective absorption bandwidth (RL<−10 dB) can move to a lower frequency band.
2022, 39(7): 3303-3316.
doi: 10.13801/j.cnki.fhclxb.20210903.004
Abstract:
The development of lightweight, broadband microwave absorbing materials to cope with severe electromagnetic pollution is a great challenge. In this paper, graphene (GR)-iron-nickel alloy (FeNi50)-polylactic acid (PLA) composites were prepared by fused deposition modeling (FDM) process, and the physical structure, micromorphology and electromagnetic properties of the composites were characterized by XRD, Raman, SEM and vector network analyzer (VNA). The effects of the GR-FeNi50 mass ratio on the microwave absorption properties of the composites were discussed. The results show that, compared with the composites without GR addition, heterogeneous interfaces triggering polarization loss are formed inside the composites, and abundant folds and pores are generated, which enhance the multiple reflections and scattering of microwaves. The minimum reflection loss reaches −40.5 dB and the effective absorption bandwidth is 4.7 GHz (13.28-18 GHz). The excellent absorption performance is attributed to the good impedance matching and the synergy between interfacial polarisation loss, dipole polarisation loss, conductivity loss and magnetic loss. In addition, the GR-FeNi50-PLA composite has advantages in terms of environmental friendliness, ease of processing and scale production compared to the absorbing materials prepared by wet chemical methods.
The development of lightweight, broadband microwave absorbing materials to cope with severe electromagnetic pollution is a great challenge. In this paper, graphene (GR)-iron-nickel alloy (FeNi50)-polylactic acid (PLA) composites were prepared by fused deposition modeling (FDM) process, and the physical structure, micromorphology and electromagnetic properties of the composites were characterized by XRD, Raman, SEM and vector network analyzer (VNA). The effects of the GR-FeNi50 mass ratio on the microwave absorption properties of the composites were discussed. The results show that, compared with the composites without GR addition, heterogeneous interfaces triggering polarization loss are formed inside the composites, and abundant folds and pores are generated, which enhance the multiple reflections and scattering of microwaves. The minimum reflection loss reaches −40.5 dB and the effective absorption bandwidth is 4.7 GHz (13.28-18 GHz). The excellent absorption performance is attributed to the good impedance matching and the synergy between interfacial polarisation loss, dipole polarisation loss, conductivity loss and magnetic loss. In addition, the GR-FeNi50-PLA composite has advantages in terms of environmental friendliness, ease of processing and scale production compared to the absorbing materials prepared by wet chemical methods.
2022, 39(7): 3317-3329.
doi: 10.13801/j.cnki.fhclxb.20210906.003
Abstract:
In this paper, gangue was purified by a series of process and gangue-supported Fe/FeOx nanoparticles (nFe/FeOx-Gangue) were prepared by the liquid-phase reduction method under open atmosphere. The factors including Fe:Gangue mass ratios, B:Fe molar ratios, and the reduction speed were investigated based on a uniform design. XRD, TEM, BET and TG-DTA analysis were used for characterization of synthesized samples. The synthesized nFe/FeOx-Gangue exists on the surface of gangue or adsorbed on surface, sharp edges and angles of small clay in series with an analogous catenulate formation in rank, indicating that the spherical particles immobilized on clay are clearly separated and well dispersed, displaying small amounts of globular or nubbly aggregates. The comparison results of several samples show that the Fe/ Gangue mass ratio (g/g) should be maintained as 1.6, and the appropriate B/Fe molar ratios are 4 or 4.5. After contacting with nFe/FeOx-Gangue for 10 min, for Cd(II), the adsorption efficiency on nFe/FeOx-Gangue is 83% at pH 5.0. The removal efficiency of Cd(II) on nFe/FeOx-Gangue is largely dependent on pH values. The reusability of nFe/FeOx-Gangue is evaluated and the results indicate that the reborn nFe/FeOx-Gangue even could adsorb 99.12% of Cd(II) ions in 5.0 mg/L solution for the sixth successive uses. nFe/FeOx-Gangue is appropriate to remove Cd(II).
In this paper, gangue was purified by a series of process and gangue-supported Fe/FeOx nanoparticles (nFe/FeOx-Gangue) were prepared by the liquid-phase reduction method under open atmosphere. The factors including Fe:Gangue mass ratios, B:Fe molar ratios, and the reduction speed were investigated based on a uniform design. XRD, TEM, BET and TG-DTA analysis were used for characterization of synthesized samples. The synthesized nFe/FeOx-Gangue exists on the surface of gangue or adsorbed on surface, sharp edges and angles of small clay in series with an analogous catenulate formation in rank, indicating that the spherical particles immobilized on clay are clearly separated and well dispersed, displaying small amounts of globular or nubbly aggregates. The comparison results of several samples show that the Fe/ Gangue mass ratio (g/g) should be maintained as 1.6, and the appropriate B/Fe molar ratios are 4 or 4.5. After contacting with nFe/FeOx-Gangue for 10 min, for Cd(II), the adsorption efficiency on nFe/FeOx-Gangue is 83% at pH 5.0. The removal efficiency of Cd(II) on nFe/FeOx-Gangue is largely dependent on pH values. The reusability of nFe/FeOx-Gangue is evaluated and the results indicate that the reborn nFe/FeOx-Gangue even could adsorb 99.12% of Cd(II) ions in 5.0 mg/L solution for the sixth successive uses. nFe/FeOx-Gangue is appropriate to remove Cd(II).
2022, 39(7): 3330-3338.
doi: 10.13801/j.cnki.fhclxb.20210913.001
Abstract:
The van der Waals heterostructure composed of a vertical stack of graphene and hexagonal boron nitride (h-BN) layered materials is an ideal model for manufacturing high-quality graphene devices. A new type of pressure sensor structure was proposed, using graphene/h-BN heterostructure on Si/SiO2 substrate as a pressure sensitive film. Through the method of molecular dynamics simulation, the stress-strain relationship between graphene and graphene/h-BN heterostructure was obtained from the molecular atomic level. It is found that the elastic modulus of single-layer graphene is about 907 GPa, and as the temperature increasing higher, the elastic modulus value will become smaller. Furthermore, the mechanical properties and temperature characteristics of the graphene/h-BN heterostructure were analyzed, and the elastic modulus of the heterostructure is 1343 GPa. The mechanical parameters of the heterostructure are less sensitive to temperature than graphene. Secondly, according to density functional theory and CASTEP, the energy change of graphene/h-BN heterostructure bonding and the geometric optimization of three different configurations were analyzed, and the AB type (One carbon is on the nitrogen, the other is on the center of hexagonal boron nitride) is the optimal configuration, and the maximum band gap opening is 3.803 eV. The band structure and density of states of this configuration were calculated. These results provide a certain theoretical basis and basis for the design and manufacture of graphene/h-BN heterostructure pressure sensors.
The van der Waals heterostructure composed of a vertical stack of graphene and hexagonal boron nitride (h-BN) layered materials is an ideal model for manufacturing high-quality graphene devices. A new type of pressure sensor structure was proposed, using graphene/h-BN heterostructure on Si/SiO2 substrate as a pressure sensitive film. Through the method of molecular dynamics simulation, the stress-strain relationship between graphene and graphene/h-BN heterostructure was obtained from the molecular atomic level. It is found that the elastic modulus of single-layer graphene is about 907 GPa, and as the temperature increasing higher, the elastic modulus value will become smaller. Furthermore, the mechanical properties and temperature characteristics of the graphene/h-BN heterostructure were analyzed, and the elastic modulus of the heterostructure is 1343 GPa. The mechanical parameters of the heterostructure are less sensitive to temperature than graphene. Secondly, according to density functional theory and CASTEP, the energy change of graphene/h-BN heterostructure bonding and the geometric optimization of three different configurations were analyzed, and the AB type (One carbon is on the nitrogen, the other is on the center of hexagonal boron nitride) is the optimal configuration, and the maximum band gap opening is 3.803 eV. The band structure and density of states of this configuration were calculated. These results provide a certain theoretical basis and basis for the design and manufacture of graphene/h-BN heterostructure pressure sensors.
2022, 39(7): 3339-3346.
doi: 10.13801/j.cnki.fhclxb.20210816.003
Abstract:
Acoustic metasurfaces are artificial materials of subwavelength thickness capable of manipulating reflection, transmission and absorption of acoustic waves. Acoustic metasurfaces have important values for space limi-ted application fields. At present, the strategy for the design of acoustic metasurfaces depends on the metamaterials. Therefore, we proposed a scheme by designing a kind of non-metamaterials acoustic metasurface to manipulate the wavefont in fluids. Based on this idea, a new type of reflection acoustic metasurface composed by the unidirectional fiber composites with periodicity was studied. Through homogenization theory and optimization method of micromechanics the fractions of composites unit cells were designed in order to obtain the effective mechani-cal and acoustics prosperities of unit cells to satisfy the densities and longitudinal velocities of discrete metasurfaces needed, as well as the impedance matching condition. Finally, the gradient longitudinal velocity of the acoustic metasurfaces needed was achieved. Using Bloch-Floquet analysis, the relationship between longitudinal velocity and frequency was studied. The band diagrams exhibit the broadband characteristics of the designed metasurfaces. Simulations of reflection control were studied for the designed metasurfaces with normally incident plan wave. Excellent wavefont manipulation effects were observed in broadband frequencies. Accordingly, it is verified that longitudinal modes are the most important factors for wave manipulation under normally incident waves. The research work provides a novel idea and potential method for the design and physical implementation of the acoustic metasurfaces as well as the other acoustic wave manipulation devices.
Acoustic metasurfaces are artificial materials of subwavelength thickness capable of manipulating reflection, transmission and absorption of acoustic waves. Acoustic metasurfaces have important values for space limi-ted application fields. At present, the strategy for the design of acoustic metasurfaces depends on the metamaterials. Therefore, we proposed a scheme by designing a kind of non-metamaterials acoustic metasurface to manipulate the wavefont in fluids. Based on this idea, a new type of reflection acoustic metasurface composed by the unidirectional fiber composites with periodicity was studied. Through homogenization theory and optimization method of micromechanics the fractions of composites unit cells were designed in order to obtain the effective mechani-cal and acoustics prosperities of unit cells to satisfy the densities and longitudinal velocities of discrete metasurfaces needed, as well as the impedance matching condition. Finally, the gradient longitudinal velocity of the acoustic metasurfaces needed was achieved. Using Bloch-Floquet analysis, the relationship between longitudinal velocity and frequency was studied. The band diagrams exhibit the broadband characteristics of the designed metasurfaces. Simulations of reflection control were studied for the designed metasurfaces with normally incident plan wave. Excellent wavefont manipulation effects were observed in broadband frequencies. Accordingly, it is verified that longitudinal modes are the most important factors for wave manipulation under normally incident waves. The research work provides a novel idea and potential method for the design and physical implementation of the acoustic metasurfaces as well as the other acoustic wave manipulation devices.
2022, 39(7): 3347-3355.
doi: 10.13801/j.cnki.fhclxb.20210818.001
Abstract:
Gallium oxide hydroxide (GaOOH) is a kind of semiconductor material with broad-band gap and has extensive potential applications in the fields such as photocatalytic degradation of organic dyes, direct methanol fuel cell, lithium ion battery, bioluminescent imaging and so on. In our study, Zn2+/GaOOH nanowires have been synthesized via a facile and controllable hydrothermal method with zinc acetate and gallium nitrate as reactants and ethylenediaminetetraacetic acid disodium salt (Na2Y) as template. The products were characterized by XRD、SEM、HRTEM and EDS techniques. The length of the as-prepared uniform Zn2+/GaOOH nanowires is up to several micrometers and the diameter is about 100 nm. Zn2+/GaOOH is single crystalline and grew along crystalline direction <110>. The phase and morphology of Zn2+/GaOOH are affected by reactants and their amounts. Keeping the reactant amount of 1.5 mmol gallium nitrate stand, Zn2+/GaOOH nanowires form with 1.0 mmol zinc acetate and 1.0-1.7 mmol Na2Y, while spinel ZnGa2O4 nanoparticles obtain with 0.5 mmol Na2Y. When the reactant amount of zinc acetate is changed to 2.0 mmol, only spinel ZnGa2O4 nanoparticles can be obtained with the reactant amount of 1.5 mmol gallium nitrate. The detail of the effects of the products by Zn∶Ga∶Y mole ratios on the phase and morphology was studied, showing the forming condition of phase-pure and uniform Zn2+/GaOOH nanowires with the Zn∶Ga∶Y mole ratio of 2∶3∶3. The result of photoluminescence determination shows that Zn2+/GaOOH nanowires exhibit strong PL emission in the blue-green wavelength range, attribute to the recombination of the defect-related excitations through an excitation-excitation collision process. The strongest PL emission is at 469 nm with the excitaton of 214 nm. The intensity of the emission peak at 469 nm rises with the blue-transiton of excitation wavelength. Zn2+/GaOOH nanowires show higher intensity of the emission peak at 469 nm by the excitation wavelength of 226 nm, accompany with ZnGa2O4 nanoparticles, indicating more excellent photoluminescence performance.
Gallium oxide hydroxide (GaOOH) is a kind of semiconductor material with broad-band gap and has extensive potential applications in the fields such as photocatalytic degradation of organic dyes, direct methanol fuel cell, lithium ion battery, bioluminescent imaging and so on. In our study, Zn2+/GaOOH nanowires have been synthesized via a facile and controllable hydrothermal method with zinc acetate and gallium nitrate as reactants and ethylenediaminetetraacetic acid disodium salt (Na2Y) as template. The products were characterized by XRD、SEM、HRTEM and EDS techniques. The length of the as-prepared uniform Zn2+/GaOOH nanowires is up to several micrometers and the diameter is about 100 nm. Zn2+/GaOOH is single crystalline and grew along crystalline direction <110>. The phase and morphology of Zn2+/GaOOH are affected by reactants and their amounts. Keeping the reactant amount of 1.5 mmol gallium nitrate stand, Zn2+/GaOOH nanowires form with 1.0 mmol zinc acetate and 1.0-1.7 mmol Na2Y, while spinel ZnGa2O4 nanoparticles obtain with 0.5 mmol Na2Y. When the reactant amount of zinc acetate is changed to 2.0 mmol, only spinel ZnGa2O4 nanoparticles can be obtained with the reactant amount of 1.5 mmol gallium nitrate. The detail of the effects of the products by Zn∶Ga∶Y mole ratios on the phase and morphology was studied, showing the forming condition of phase-pure and uniform Zn2+/GaOOH nanowires with the Zn∶Ga∶Y mole ratio of 2∶3∶3. The result of photoluminescence determination shows that Zn2+/GaOOH nanowires exhibit strong PL emission in the blue-green wavelength range, attribute to the recombination of the defect-related excitations through an excitation-excitation collision process. The strongest PL emission is at 469 nm with the excitaton of 214 nm. The intensity of the emission peak at 469 nm rises with the blue-transiton of excitation wavelength. Zn2+/GaOOH nanowires show higher intensity of the emission peak at 469 nm by the excitation wavelength of 226 nm, accompany with ZnGa2O4 nanoparticles, indicating more excellent photoluminescence performance.
2022, 39(7): 3356-3368.
doi: 10.13801/j.cnki.fhclxb.20210929.002
Abstract:
The purpose is to further develop the new application of energy-absorbing materials in the field of road. A new type of road energy-absorbing material with excellent mechanical properties, energy absorbing property and cushion property was prepared. The suitable curing time was determined. The mechanical properties, energy absorption characteristics and cushion effect of different types of road energy-absorbing materials were clarified. On this basis, the comprehensive property evaluation system of road energy-absorbing materials based on multi index decision-making was established. Type II elastomeric polymer (EP-Ⅱ) was used as the basic energy-absorbing material. The optimum scheme of composition ratio of road energy-absorbing materials was recommended. It lays a solid foundation for the further popularization and application of energy-absorbing materials in road engineering. The results show that both polyvinyl alcohol (PVA) fiber and ultra high molecular weight polyethylene (UHMWPE) micropowder can effectively improve the mechanical properties and energy absorption properties of Type Ⅱ elastomeric polymer, but the effect of the latter is more significant; Both of them can enhance the performance of basic energy absorbing materials. The tensile properties, tearing properties and energy absorption properties are improved by 127.4%-129.11%, 34.04% and 101.65% respectively; Considering the working properties and economic benefits, the optimum scheme of the recommended road energy-absorbing material is 1.0wt% PVA-3wt% UHMWPE/EP-Ⅱ. The corresponding working property indicators are: tensile strength 14.29 MPa, elongation at break 703.36%, tear strength 79.27 N/mm, absorbed conversion energy 1.73 J, and the minimum buffer factor 10.21.
The purpose is to further develop the new application of energy-absorbing materials in the field of road. A new type of road energy-absorbing material with excellent mechanical properties, energy absorbing property and cushion property was prepared. The suitable curing time was determined. The mechanical properties, energy absorption characteristics and cushion effect of different types of road energy-absorbing materials were clarified. On this basis, the comprehensive property evaluation system of road energy-absorbing materials based on multi index decision-making was established. Type II elastomeric polymer (EP-Ⅱ) was used as the basic energy-absorbing material. The optimum scheme of composition ratio of road energy-absorbing materials was recommended. It lays a solid foundation for the further popularization and application of energy-absorbing materials in road engineering. The results show that both polyvinyl alcohol (PVA) fiber and ultra high molecular weight polyethylene (UHMWPE) micropowder can effectively improve the mechanical properties and energy absorption properties of Type Ⅱ elastomeric polymer, but the effect of the latter is more significant; Both of them can enhance the performance of basic energy absorbing materials. The tensile properties, tearing properties and energy absorption properties are improved by 127.4%-129.11%, 34.04% and 101.65% respectively; Considering the working properties and economic benefits, the optimum scheme of the recommended road energy-absorbing material is 1.0wt% PVA-3wt% UHMWPE/EP-Ⅱ. The corresponding working property indicators are: tensile strength 14.29 MPa, elongation at break 703.36%, tear strength 79.27 N/mm, absorbed conversion energy 1.73 J, and the minimum buffer factor 10.21.
2022, 39(7): 3369-3375.
doi: 10.13801/j.cnki.fhclxb.20210927.001
Abstract:
The development of visible-light-responsive metal organic framework materials (MOFs) heterojunctions is expected to make efficient use of solar energy for catalytic degradation/detoxification of environmental pollutants. Using zircomiun tetrachloride (ZrCl4) and 2-aminoterephthalic acid (2-ATA) as raw materials, NH2-UiO-66(Zr) was prepared as MOFs substrate by solvothermal method. A series of AgI/NH2-UiO-66(Zr) heterojunction composites were prepared by counter ion deposition method. The materials were characterized by XRD, BET, TEM, UV-Vis DRS, FT-IR, TGA and photoelectrochemical tests. Taking Cr(VI) as a model pollutant, the photocatalytic performance of the composite was studied under visible light and various factors were also investigated, including pH, initial Cr(VI) concentration, catalyst loading amount, type and concentration of trapping agent. It is found that 20% AgI/NH2-UiO-66(Zr) displays optimal photocatalytic performance. After 120 min of visible light irradiation, the Cr(VI) reduction efficiency is 97.8%, which is much higher than that of naked AgI and NH2-UiO-66(Zr). The fitted first-order kinetic constant k is 7.9 and 7.4 times that in the AgI and NH2-UiO-66(Zr) systems, respectively. In addition, the catalyst has good cyclic stability. After 5 cycles, the reduction rate of Cr(VI) still remain at about 90%.
The development of visible-light-responsive metal organic framework materials (MOFs) heterojunctions is expected to make efficient use of solar energy for catalytic degradation/detoxification of environmental pollutants. Using zircomiun tetrachloride (ZrCl4) and 2-aminoterephthalic acid (2-ATA) as raw materials, NH2-UiO-66(Zr) was prepared as MOFs substrate by solvothermal method. A series of AgI/NH2-UiO-66(Zr) heterojunction composites were prepared by counter ion deposition method. The materials were characterized by XRD, BET, TEM, UV-Vis DRS, FT-IR, TGA and photoelectrochemical tests. Taking Cr(VI) as a model pollutant, the photocatalytic performance of the composite was studied under visible light and various factors were also investigated, including pH, initial Cr(VI) concentration, catalyst loading amount, type and concentration of trapping agent. It is found that 20% AgI/NH2-UiO-66(Zr) displays optimal photocatalytic performance. After 120 min of visible light irradiation, the Cr(VI) reduction efficiency is 97.8%, which is much higher than that of naked AgI and NH2-UiO-66(Zr). The fitted first-order kinetic constant k is 7.9 and 7.4 times that in the AgI and NH2-UiO-66(Zr) systems, respectively. In addition, the catalyst has good cyclic stability. After 5 cycles, the reduction rate of Cr(VI) still remain at about 90%.
2022, 39(7): 3376-3387.
doi: 10.13801/j.cnki.fhclxb.20210916.005
Abstract:
Selective hydrogenation of 1,3-butadiene is an effective strategy to remove 1,3-butadiene in the petrochemical industry. ZIF-67 supported monometallic Pd (Pd/ZIF-67) and bimetallic Pd–Cu catalysts (PdCu/ZIF-67) with different Pd:Cu molar ratios (1∶3–3∶1) were synthesized by impregnation and hydrogen reduction. The prepared Pd/ZIF-67 and PdCu/ZIF-67 catalysts were characterized using XRD, N2 adsorption-desorption analysis, TEM, EDS, XPS and ICP-AES. The catalytic performance of supported Pd/ZIF-67 and PdCu/ZIF-67 catalysts were studied in the selective hydrogenation of 1,3-butadiene on the fixed-bed flow quartz reactor under atmospheric pressure. The XPS studies at Pd3d levels and Cu2p levels reveal that Pd and Cu particles on the surface of the ZIF-67 support are in a +2 valence state. TEM and EDS display that Pd nanoparticles and Pd–Cu nanoparticles are uniformly dispersed on ZIF-67. The experiment results show that the catalytic activity of PdCu/ZIF-67(1∶1) is lower than that of Pd/ZIF-67 due to strong interaction between Pd–Cu and ZIF-67 support and the geometric effects, i.e., dilution of blocking of a fraction of the palladium surface by copper. The 1,3-butadiene conversion and butene selectivity reach 99.9% and 79.6% for Pd/ZIF-67 at 50℃, respectively. For the PdCu/ZIF-67(1∶1) catalyst, the 1,3-butadiene conversion and butene selectivity are 93.2% and 64.3% at 130℃ within 7 h, respectively. The hydrogenation activity of PdCu/ZIF-67 catalyst decrease with increasing of Cu content, while the butene selectivity increase. PdCu/ZIF-67(1∶1) show higher stability than Pd/ZIF-67, the conversion of 1,3-butadiene and butene selectivity almost remain the same after continuous run for 50 h at 130℃. The results provide a reference for the design of new high efficiency 1,3-butadiene hydrogenation catalyst.
Selective hydrogenation of 1,3-butadiene is an effective strategy to remove 1,3-butadiene in the petrochemical industry. ZIF-67 supported monometallic Pd (Pd/ZIF-67) and bimetallic Pd–Cu catalysts (PdCu/ZIF-67) with different Pd:Cu molar ratios (1∶3–3∶1) were synthesized by impregnation and hydrogen reduction. The prepared Pd/ZIF-67 and PdCu/ZIF-67 catalysts were characterized using XRD, N2 adsorption-desorption analysis, TEM, EDS, XPS and ICP-AES. The catalytic performance of supported Pd/ZIF-67 and PdCu/ZIF-67 catalysts were studied in the selective hydrogenation of 1,3-butadiene on the fixed-bed flow quartz reactor under atmospheric pressure. The XPS studies at Pd3d levels and Cu2p levels reveal that Pd and Cu particles on the surface of the ZIF-67 support are in a +2 valence state. TEM and EDS display that Pd nanoparticles and Pd–Cu nanoparticles are uniformly dispersed on ZIF-67. The experiment results show that the catalytic activity of PdCu/ZIF-67(1∶1) is lower than that of Pd/ZIF-67 due to strong interaction between Pd–Cu and ZIF-67 support and the geometric effects, i.e., dilution of blocking of a fraction of the palladium surface by copper. The 1,3-butadiene conversion and butene selectivity reach 99.9% and 79.6% for Pd/ZIF-67 at 50℃, respectively. For the PdCu/ZIF-67(1∶1) catalyst, the 1,3-butadiene conversion and butene selectivity are 93.2% and 64.3% at 130℃ within 7 h, respectively. The hydrogenation activity of PdCu/ZIF-67 catalyst decrease with increasing of Cu content, while the butene selectivity increase. PdCu/ZIF-67(1∶1) show higher stability than Pd/ZIF-67, the conversion of 1,3-butadiene and butene selectivity almost remain the same after continuous run for 50 h at 130℃. The results provide a reference for the design of new high efficiency 1,3-butadiene hydrogenation catalyst.
2022, 39(7): 3388-3403.
doi: 10.13801/j.cnki.fhclxb.20210909.009
Abstract:
The T-section concrete filled steel and glass fiber reinforced polymer (GFRP) tubular composite column (T-SCFC) is composed of external steel tube, sandwich concrete, GFRP tube and core concrete. Axial compression tests were carried out on 14 confined concrete short columns with different cross-section forms and three groups of concrete-filled steel tubular T-section columns with different wall thicknesses of GFRP tube. The mechanical properties of square concrete filled steel tube (CFST), concrete filled FRP tube (CFFT), steel-concrete-FRP-concrete (SCFC) short columns and T-SCFC columns under axial compression were compared and analyzed. The finite element model with the same size as the specimen was established, and the numerical parameter analysis was carried out to study the influence of steel tube wall thickness and core concrete strength on the axial compression performance of T-SCFC columns. The results show that the built-in GFRP tube can significantly improve the compression performance of concrete filled square steel tubular short columns, and significantly delay the steel yield and buckling of SCFC short columns under axial compression load. Before the peak load, the load-axial displacement curve of T-SCFC column increases bilinearly, and the residual bearing capacity of the specimen maintains high after fracture of the GFRP. The fracture of GFRP can be used as the failure point of the composite column. Increasing the wall thickness of GFRP tube can significantly improve the bearing capacity of the specimen. The calculation results of the finite element model are in good agreement with the test. Increasing the wall thickness of the steel tube can significantly improve the bearing capacity of the specimen. Improving the strength of the core concrete of the specimen only has a certain effect on the equivalent yield load of the specimen, and has little effect on the peak bearing capacity of the specimen.
The T-section concrete filled steel and glass fiber reinforced polymer (GFRP) tubular composite column (T-SCFC) is composed of external steel tube, sandwich concrete, GFRP tube and core concrete. Axial compression tests were carried out on 14 confined concrete short columns with different cross-section forms and three groups of concrete-filled steel tubular T-section columns with different wall thicknesses of GFRP tube. The mechanical properties of square concrete filled steel tube (CFST), concrete filled FRP tube (CFFT), steel-concrete-FRP-concrete (SCFC) short columns and T-SCFC columns under axial compression were compared and analyzed. The finite element model with the same size as the specimen was established, and the numerical parameter analysis was carried out to study the influence of steel tube wall thickness and core concrete strength on the axial compression performance of T-SCFC columns. The results show that the built-in GFRP tube can significantly improve the compression performance of concrete filled square steel tubular short columns, and significantly delay the steel yield and buckling of SCFC short columns under axial compression load. Before the peak load, the load-axial displacement curve of T-SCFC column increases bilinearly, and the residual bearing capacity of the specimen maintains high after fracture of the GFRP. The fracture of GFRP can be used as the failure point of the composite column. Increasing the wall thickness of GFRP tube can significantly improve the bearing capacity of the specimen. The calculation results of the finite element model are in good agreement with the test. Increasing the wall thickness of the steel tube can significantly improve the bearing capacity of the specimen. Improving the strength of the core concrete of the specimen only has a certain effect on the equivalent yield load of the specimen, and has little effect on the peak bearing capacity of the specimen.
2022, 39(7): 3404-3414.
doi: 10.13801/j.cnki.fhclxb.20210729.002
Abstract:
Engineering cementitious composite (ECC) is widely used in structural seismic strengthening, and its fatigue performance is the focus of engineering. The uniaxial tensile cyclic loading test of ECC specimens was carried out by fatigue testing machine, and the development law of dynamic deformation, damage model and fatigue life was analyzed. The results show that under uniaxial tensile fatigue load, the stress-strain curve of ECC is sparse-dense-sparse. Residual strain develops in three stages and is described by six polynomial fitting. The correlation coefficient is basically greater than 0.9. Two physical quantities, strain rate and strain growth rate, are defined for the second stage. It is found that the higher the tensile stress ratio is, the larger the strain rate is and the shorter the cycle ratio is in the second stage. Strain growth rate varies from 0.0028 to 0.0098 and decreases with the increase of tensile stress ratio. The damage variable is defined by fatigue deformation modulus, and the two-stage fatigue damage evolution equation is established with the cycle life ratio n/N=0.7. The stress ratio
Engineering cementitious composite (ECC) is widely used in structural seismic strengthening, and its fatigue performance is the focus of engineering. The uniaxial tensile cyclic loading test of ECC specimens was carried out by fatigue testing machine, and the development law of dynamic deformation, damage model and fatigue life was analyzed. The results show that under uniaxial tensile fatigue load, the stress-strain curve of ECC is sparse-dense-sparse. Residual strain develops in three stages and is described by six polynomial fitting. The correlation coefficient is basically greater than 0.9. Two physical quantities, strain rate and strain growth rate, are defined for the second stage. It is found that the higher the tensile stress ratio is, the larger the strain rate is and the shorter the cycle ratio is in the second stage. Strain growth rate varies from 0.0028 to 0.0098 and decreases with the increase of tensile stress ratio. The damage variable is defined by fatigue deformation modulus, and the two-stage fatigue damage evolution equation is established with the cycle life ratio n/N=0.7. The stress ratio
2022, 39(7): 3415-3427.
doi: 10.13801/j.cnki.fhclxb.20210804.003
Abstract:
The improvement methods and strength properties of scrap tire granular materials are the research basis on the frost resistance performance improvement of piles in cold regions. Several composite samples were made according to the mass ratio of rubber∶sand∶polyurethane = 3∶2∶1. The stress-strain curves of samples under different temperatures, confining pressures and number of freeze-thaw cycles were obtained by triaxial tests. The test results show that the stress-strain curve of rubber-sand-polyurethane composite has no obvious peak point, and has obvious strain hardening characteristic. The failure strength of the sample increases with the decrease of temperature, and increases by 15.0% when the test temperature decreases by 5.0℃ for frozen samples. The failure strength values of samples decrease with the increase of freeze-thaw cycles, but the average decrease is less than 5.0%. The effect of confining pressures on the failure strength of the 20.0℃ sample is about 15.0%, while that of the frozen samples is less than 5.0%. The sensitivity analysis shows that the temperature has the greatest impact on the failure strength of rubber-sand-polyurethane composites, while the confining pressure and the number of freeze-thaw cycles have little effect. The rubber-sand-polyurethane composites have the characteristics of moderate strength, stable structure and freeze-thaw resistance. The stress-strain constitutive model of rubber-sand-polyurethane composite after consideration of the temperature, confining pressure and freeze-thaw cycle was established, and the rationality of the model parameters fitting formula was verified.
The improvement methods and strength properties of scrap tire granular materials are the research basis on the frost resistance performance improvement of piles in cold regions. Several composite samples were made according to the mass ratio of rubber∶sand∶polyurethane = 3∶2∶1. The stress-strain curves of samples under different temperatures, confining pressures and number of freeze-thaw cycles were obtained by triaxial tests. The test results show that the stress-strain curve of rubber-sand-polyurethane composite has no obvious peak point, and has obvious strain hardening characteristic. The failure strength of the sample increases with the decrease of temperature, and increases by 15.0% when the test temperature decreases by 5.0℃ for frozen samples. The failure strength values of samples decrease with the increase of freeze-thaw cycles, but the average decrease is less than 5.0%. The effect of confining pressures on the failure strength of the 20.0℃ sample is about 15.0%, while that of the frozen samples is less than 5.0%. The sensitivity analysis shows that the temperature has the greatest impact on the failure strength of rubber-sand-polyurethane composites, while the confining pressure and the number of freeze-thaw cycles have little effect. The rubber-sand-polyurethane composites have the characteristics of moderate strength, stable structure and freeze-thaw resistance. The stress-strain constitutive model of rubber-sand-polyurethane composite after consideration of the temperature, confining pressure and freeze-thaw cycle was established, and the rationality of the model parameters fitting formula was verified.
2022, 39(7): 3428-3440.
doi: 10.13801/j.cnki.fhclxb.20210816.004
Abstract:
In order to study the flexural performance of reinforced concrete (RC) beams strengthened by high-strength steel wire strand (HSSWS) meshes reinforced engineered cementitious composites (ECC), the bending tests were performed on seven non-damaged RC beams considering the influence factors such as the steel strand diameter, the longitudinal steel strand reinforcement rate, formula of ECC and end anchorage. The results show that under the condition of using reasonable anchorage measures at the end of the reinforcement layer, the bearing capacity, ductility and crack-control capacity of RC beams strengthened by HSSWS meshes reinforced ECC in bending can be significantly improved, and the crack development of the original RC beam can be effectively delayed, which results in reducing crack width. The increase of longitudinal HSSWS reinforcement rate will improve the cracking load, bearing capacity, crack-control capacity and stiffness of the strengthened beams in bending, but excessive HSSWS reinforcement rate of the strengthened beams would reduce the ductility and toughness. When the reinforcement ratio of longitudinal HSSWS is close, the ductility, toughness and crack-control ability of strengthened beams would be reduced to some extent by using the HSSWS with relative large diameter. The cracking load, bearing capacity and stiffness of strengthened beams in bending increase with the increases of elastic modulus and tensile strength of ECC. The crack-control ability, ductility and toughness of strengthened beams increase with the increase of ultimate tensile strain of ECC.
In order to study the flexural performance of reinforced concrete (RC) beams strengthened by high-strength steel wire strand (HSSWS) meshes reinforced engineered cementitious composites (ECC), the bending tests were performed on seven non-damaged RC beams considering the influence factors such as the steel strand diameter, the longitudinal steel strand reinforcement rate, formula of ECC and end anchorage. The results show that under the condition of using reasonable anchorage measures at the end of the reinforcement layer, the bearing capacity, ductility and crack-control capacity of RC beams strengthened by HSSWS meshes reinforced ECC in bending can be significantly improved, and the crack development of the original RC beam can be effectively delayed, which results in reducing crack width. The increase of longitudinal HSSWS reinforcement rate will improve the cracking load, bearing capacity, crack-control capacity and stiffness of the strengthened beams in bending, but excessive HSSWS reinforcement rate of the strengthened beams would reduce the ductility and toughness. When the reinforcement ratio of longitudinal HSSWS is close, the ductility, toughness and crack-control ability of strengthened beams would be reduced to some extent by using the HSSWS with relative large diameter. The cracking load, bearing capacity and stiffness of strengthened beams in bending increase with the increases of elastic modulus and tensile strength of ECC. The crack-control ability, ductility and toughness of strengthened beams increase with the increase of ultimate tensile strain of ECC.
2022, 39(7): 3441-3450.
doi: 10.13801/j.cnki.fhclxb.20210916.002
Abstract:
In the past few decades, superhydrophobic surfaces have received extensive attention due to their special properties. However, in outdoor applications, most superhydrophobic surfaces easily lose their superhydrophobicity due to various factors in the environment. A simple two-step dip-coating method is used to prepare a strong and repairable superhydrophobic coating. In the first step, the coating’s bottom layer was prepared by mixing polysiloxane with absolute ethanol. For the second step, neutral silicone glass glue was mixed with silicon dioxide nanoparticles, micron attapulgite powder (ATP) and polysiloxane to create the coating’s upper layer. Scanning electron microscopy (SEM), contact angle measuring instrument, and fourier-transform infrared spectroscopy (FTIR) were used to determine the microscopic morphology, wettability and molecular structure of the coating. Furthermore, the optimal amount of neutral silicone glass glue was specified while at the same time the coating’s self-healing ability was observed under mechanical abrasion and in an acid-based environment. The results show that the hydrophobicity of the coating reaches the optimum when the amount of neutral silicone glass glue is 1% and the water contact angle reaches 153.5°±1.5°. In this way, the coating is able to maintain a water contact angle of over 140° even when 360 cm of mechanical wear with a weight of 50 g (1.03 kPa) is placed on it. In addition, after the coating has endured a certain amount of mechanical abrasion and acid-base damage, the superhydrophobic properties of the coating can be repaired by high-temperature heating. The coating also provides a certain water resistance-stability and an excellent self-cleaning ability.
In the past few decades, superhydrophobic surfaces have received extensive attention due to their special properties. However, in outdoor applications, most superhydrophobic surfaces easily lose their superhydrophobicity due to various factors in the environment. A simple two-step dip-coating method is used to prepare a strong and repairable superhydrophobic coating. In the first step, the coating’s bottom layer was prepared by mixing polysiloxane with absolute ethanol. For the second step, neutral silicone glass glue was mixed with silicon dioxide nanoparticles, micron attapulgite powder (ATP) and polysiloxane to create the coating’s upper layer. Scanning electron microscopy (SEM), contact angle measuring instrument, and fourier-transform infrared spectroscopy (FTIR) were used to determine the microscopic morphology, wettability and molecular structure of the coating. Furthermore, the optimal amount of neutral silicone glass glue was specified while at the same time the coating’s self-healing ability was observed under mechanical abrasion and in an acid-based environment. The results show that the hydrophobicity of the coating reaches the optimum when the amount of neutral silicone glass glue is 1% and the water contact angle reaches 153.5°±1.5°. In this way, the coating is able to maintain a water contact angle of over 140° even when 360 cm of mechanical wear with a weight of 50 g (1.03 kPa) is placed on it. In addition, after the coating has endured a certain amount of mechanical abrasion and acid-base damage, the superhydrophobic properties of the coating can be repaired by high-temperature heating. The coating also provides a certain water resistance-stability and an excellent self-cleaning ability.
2022, 39(7): 3451-3461.
doi: 10.13801/j.cnki.fhclxb.20210716.006
Abstract:
The failure process and failure modes of ultra-high performance concrete (UHPC) stub columns were investigated through the axial compression capacity test of ten groups of UHPC stub columns with diamond-shaped and cross-shaped composite stirrups and one group of columns without steel bars. The effects of stirrup spacing, fiber content and stirrup form on their axial strain-axial load curve and stress-strain curve were analyzed. Results show that increasing numbers of closed loops in the form of stirrups and fiber content could improve the deformed capacity of UHPC stub columns. The effects of stirrup spacing and fiber content on the axial compression bearing capacity and corresponding axial peak strain of the UHPC are significant. The impact of stirrup spacing on the axial peak strain is greater. The peak load of diamond-shaped composite stirrups (DC) with the same stirrup spacing is higher than that of cross-shaped composite stirrups (CC) specimens. As the spacing of stirrups decreases, the slope of the ascending section of the UHPC normalized stress-strain curve of each specimen increases, at the same time the differences of descending sections are more significant. The effects of fiber content and different types of stirrups on the stress-strain normalized curve of UHPC specimens are small. Considering the restraint effect of stirrups and fiber restraint, the calculation formula of axial compression capacity of UHPC short columns constrained by composite stirrups was proposed. The calculation results are in good agreement with the experimental results.
The failure process and failure modes of ultra-high performance concrete (UHPC) stub columns were investigated through the axial compression capacity test of ten groups of UHPC stub columns with diamond-shaped and cross-shaped composite stirrups and one group of columns without steel bars. The effects of stirrup spacing, fiber content and stirrup form on their axial strain-axial load curve and stress-strain curve were analyzed. Results show that increasing numbers of closed loops in the form of stirrups and fiber content could improve the deformed capacity of UHPC stub columns. The effects of stirrup spacing and fiber content on the axial compression bearing capacity and corresponding axial peak strain of the UHPC are significant. The impact of stirrup spacing on the axial peak strain is greater. The peak load of diamond-shaped composite stirrups (DC) with the same stirrup spacing is higher than that of cross-shaped composite stirrups (CC) specimens. As the spacing of stirrups decreases, the slope of the ascending section of the UHPC normalized stress-strain curve of each specimen increases, at the same time the differences of descending sections are more significant. The effects of fiber content and different types of stirrups on the stress-strain normalized curve of UHPC specimens are small. Considering the restraint effect of stirrups and fiber restraint, the calculation formula of axial compression capacity of UHPC short columns constrained by composite stirrups was proposed. The calculation results are in good agreement with the experimental results.
2022, 39(7): 3462-3468.
doi: 10.13801/j.cnki.fhclxb.20210906.006
Abstract:
In order to meet the increasing requirements of wearable electronic devices, low-cost, high-performance flexible supercapacitors have become a research hotspot. In this work, flexible, self-standing PANI-CHF-GEL electrode was obtained by growing polyaniline (PANI) on the surface of corn husk fiber (CHF) and mixed with polyvinyl alcohol/sulfuric acid (PVA/H2SO4) gel, followed by a facile frozen-thawing method. PANI-CHF-GEL exhibits excellent mechanical properties (a fracture strength of 259 kPa at a fracture strain of 121%) and good toughness (a fracture energy of 0.167 MJ·cm−3). Employing PVA/H2SO4 as the gel electrolyte, the symmetric PANI-CHF-GEL//PANI-CHF-GEL solid supercapacitor delivers an areal capacitance of 1789.74 mF·cm−2, a power density of 0.34 mW·cm−2, and a corresponding energy density of 3.51 mW·h·cm−2 (@3.00 mA·cm−2). Moreover, the device retains its original properties even bent 90°, indicating its promise potentials for wearable electronics.
In order to meet the increasing requirements of wearable electronic devices, low-cost, high-performance flexible supercapacitors have become a research hotspot. In this work, flexible, self-standing PANI-CHF-GEL electrode was obtained by growing polyaniline (PANI) on the surface of corn husk fiber (CHF) and mixed with polyvinyl alcohol/sulfuric acid (PVA/H2SO4) gel, followed by a facile frozen-thawing method. PANI-CHF-GEL exhibits excellent mechanical properties (a fracture strength of 259 kPa at a fracture strain of 121%) and good toughness (a fracture energy of 0.167 MJ·cm−3). Employing PVA/H2SO4 as the gel electrolyte, the symmetric PANI-CHF-GEL//PANI-CHF-GEL solid supercapacitor delivers an areal capacitance of 1789.74 mF·cm−2, a power density of 0.34 mW·cm−2, and a corresponding energy density of 3.51 mW·h·cm−2 (@3.00 mA·cm−2). Moreover, the device retains its original properties even bent 90°, indicating its promise potentials for wearable electronics.
2022, 39(7): 3469-3477.
doi: 10.13801/j.cnki.fhclxb.20211014.002
Abstract:
Cancer is a disease with the highest mortality rate in the world, developing new cancer drugs is also a very exploratory research. In this paper, spindle-shaped iron hydroxyl oxide (FeOOH NPs) was firstly prepared as a nanocarrier to polymerise pyrrole (Py) to get iron hydroxyl oxide @polypyrrole (FeOOH@PPy) composite nano-material. The structure and properties of FeOOH@PPy were characterized by FTIR, DLS, TEM and UV-vis, etc. The photothermal conversion experiments proved that the composite nanoparticles had excellent photothermal conversion properties, and the biocompatibility and application potential of the composite nanomaterial in tumor therapy were explored. The results show that the average particle size of the obtained nanoparticles is about 100 nm, and has good stability in the aqueous solution. The results of the photothermal performance test show that FeOOH@PPy composite nanoparticles can absorb 808 nm near-infrared light and convert it into enough heattotrigger the apoptosis of tumor cells. In a 14 days treatment on 4T1 breast cancer mouse model, FeOOH@PPy composite nanoparticles show excellent antitumor effect. Tissue analysis show that the composite nanoparticles have no significant effect on normal tissues of mice, suggesting that the composite nanoparticles have the potential as photothermal therapy agent.
Cancer is a disease with the highest mortality rate in the world, developing new cancer drugs is also a very exploratory research. In this paper, spindle-shaped iron hydroxyl oxide (FeOOH NPs) was firstly prepared as a nanocarrier to polymerise pyrrole (Py) to get iron hydroxyl oxide @polypyrrole (FeOOH@PPy) composite nano-material. The structure and properties of FeOOH@PPy were characterized by FTIR, DLS, TEM and UV-vis, etc. The photothermal conversion experiments proved that the composite nanoparticles had excellent photothermal conversion properties, and the biocompatibility and application potential of the composite nanomaterial in tumor therapy were explored. The results show that the average particle size of the obtained nanoparticles is about 100 nm, and has good stability in the aqueous solution. The results of the photothermal performance test show that FeOOH@PPy composite nanoparticles can absorb 808 nm near-infrared light and convert it into enough heattotrigger the apoptosis of tumor cells. In a 14 days treatment on 4T1 breast cancer mouse model, FeOOH@PPy composite nanoparticles show excellent antitumor effect. Tissue analysis show that the composite nanoparticles have no significant effect on normal tissues of mice, suggesting that the composite nanoparticles have the potential as photothermal therapy agent.
2022, 39(7): 3478-3484.
doi: 10.13801/j.cnki.fhclxb.20210817.002
Abstract:
In order to improve the mechanical properties and water resistance of thermoplastic starch (TPS), the carboxylated silica microspheres (SM-COOH) modified by coupling agent KH550 and succinic anhydride were used to prepare the SM-COOH/TPS composites by extrusion and injection molding process. The effects of different contents of SM-COOH on the mechanical properties, dynamic thermodynamics, thermal stability, surface water resistance and rheological properties of the composites were studied in details. The results show that the added SM-COOH can improve the performance of TPS. When the content of SM-COOH is 2.0wt%, the tensile strength and impact strength of the composites reach the maximum value of 12.71 MPa and 15.918 kJ/m2, respectively, which are nearly 4 times and 2.6 times higher than that of pure TPS. The temperature corresponding to the maximum decomposition rate in DTG curves reaches the maximum of 322.1℃, and the peak value and equilibrium torque of the composites are moderate, which shows the better rheological processing properties. In addition, with the increased SM-COOH content, the transition temperature and surface contact angle of composites also increase. Therefore, adding the carboxylated modified nano-SiO2 into TPS is an effective method to improve the performance of SM-COOH/TPS composites, and will be useful in the area of starch-based biodegradable plastics.
In order to improve the mechanical properties and water resistance of thermoplastic starch (TPS), the carboxylated silica microspheres (SM-COOH) modified by coupling agent KH550 and succinic anhydride were used to prepare the SM-COOH/TPS composites by extrusion and injection molding process. The effects of different contents of SM-COOH on the mechanical properties, dynamic thermodynamics, thermal stability, surface water resistance and rheological properties of the composites were studied in details. The results show that the added SM-COOH can improve the performance of TPS. When the content of SM-COOH is 2.0wt%, the tensile strength and impact strength of the composites reach the maximum value of 12.71 MPa and 15.918 kJ/m2, respectively, which are nearly 4 times and 2.6 times higher than that of pure TPS. The temperature corresponding to the maximum decomposition rate in DTG curves reaches the maximum of 322.1℃, and the peak value and equilibrium torque of the composites are moderate, which shows the better rheological processing properties. In addition, with the increased SM-COOH content, the transition temperature and surface contact angle of composites also increase. Therefore, adding the carboxylated modified nano-SiO2 into TPS is an effective method to improve the performance of SM-COOH/TPS composites, and will be useful in the area of starch-based biodegradable plastics.
2022, 39(7): 3485-3497.
doi: 10.13801/j.cnki.fhclxb.20210902.006
Abstract:
In order to study the effect of rolling with heated roll on the microstructure and properties of laminated composites, Al/AZ31B/Al laminated composites were fabricated by multi-passes RHR in this paper. The influences of different reduction and annealing temperatures on the interfacial morphology and bonding properties of the composites were analyzed by OM, XRD, SEM and design mold tests. The results show that the rolling with heated roll has a deformation and promoting the formation of a diffusion layer, and the discontinuous diffusion layer is formed at bonding interface of composite sheets under high reduction. With the increase of the reduction, the bonding surface gradually presents a significant “wave” type from flat, and the shear slopes occur in pairs with similar angles. The excessive reduction leads to difficulty in the coordination of the deformation process of heterogeneous materials, and the cracks appear in some areas of the decreasing direction of the magnesium layer thickness. After annealing, the Al/Mg bonding interface forms more effective metallurgical bonding. With the increase of annealing temperature, the thickness of the diffusion layer increases, and there is a delamination phenomenon. The intermetallic compounds are Al3Mg2 (β phase) and Mg17Al12 (γ phase). The peeling morphology is quasi-cleavage fracture. When the annealing temperature is too high, the sheet-shaped intermetallic compound becomes thicker, and the two metal plates will be crackled from the intermetallic compound layer. When the reduction is 60%-70% and the annealing temperature is 200-250℃, the bonding strength of the composite sheet by multi-passes rolling with heated roll is improved.
In order to study the effect of rolling with heated roll on the microstructure and properties of laminated composites, Al/AZ31B/Al laminated composites were fabricated by multi-passes RHR in this paper. The influences of different reduction and annealing temperatures on the interfacial morphology and bonding properties of the composites were analyzed by OM, XRD, SEM and design mold tests. The results show that the rolling with heated roll has a deformation and promoting the formation of a diffusion layer, and the discontinuous diffusion layer is formed at bonding interface of composite sheets under high reduction. With the increase of the reduction, the bonding surface gradually presents a significant “wave” type from flat, and the shear slopes occur in pairs with similar angles. The excessive reduction leads to difficulty in the coordination of the deformation process of heterogeneous materials, and the cracks appear in some areas of the decreasing direction of the magnesium layer thickness. After annealing, the Al/Mg bonding interface forms more effective metallurgical bonding. With the increase of annealing temperature, the thickness of the diffusion layer increases, and there is a delamination phenomenon. The intermetallic compounds are Al3Mg2 (β phase) and Mg17Al12 (γ phase). The peeling morphology is quasi-cleavage fracture. When the annealing temperature is too high, the sheet-shaped intermetallic compound becomes thicker, and the two metal plates will be crackled from the intermetallic compound layer. When the reduction is 60%-70% and the annealing temperature is 200-250℃, the bonding strength of the composite sheet by multi-passes rolling with heated roll is improved.
2022, 39(7): 3498-3509.
doi: 10.13801/j.cnki.fhclxb.20210915.001
Abstract:
To solve the problems of low surface hardness and poor wear resistance of nickel copper (NiCu) alloy, the effects of WC with different particle sizes on the microstructure, microhardness, wear resistance and electrochemical corrosion resistance of the coating were studied. In this paper, the NiCu alloy coating, 60wt% coarse WC/NiCu composite coating and 60wt% fine WC/NiCu composite coating were prepared on A3 steel by laser melting deposition (LMD). The microstructure was characterized by scanning electron microscope, X-ray spectrometer and optical microscope. The microhardness and wear resistance of the coating were measured by microhardness tester and wear tester. The electrochemical corrosion resistance of NiCu alloy coating and composite coating were tested and analyzed by electrochemical workstation. The results show that the three coatings have formed a good metallurgical bond with the substrate, without obvious cracks and pores under the suitable parameters. The microstructures of cladding layer are mainly equiaxial and columnar, and the size of the grains is obviously reduced by the addition of WC. Compared with the NiCu coating, the microhardness of the coating with 60wt% coarse WC and fine WC increase by 62.1% and 81.1%, respectively, and the wear loss decrease by 84.8% and 94.3%, respectively. The wear mechanism is mainly abrasive wear. In 3.5wt%NaCl solution, the self-corrosion current density of the composite coating is 61% and 49% lower than that of NiCu alloy coating, respectively. The addition of WC significantly improves the performance of the NiCu alloy coating. The fine WC has a more obvious effect on the improvement of microhardness and wear resistance, and the coarse WC has an obvious improvement on the electrochemical corrosion performance.
To solve the problems of low surface hardness and poor wear resistance of nickel copper (NiCu) alloy, the effects of WC with different particle sizes on the microstructure, microhardness, wear resistance and electrochemical corrosion resistance of the coating were studied. In this paper, the NiCu alloy coating, 60wt% coarse WC/NiCu composite coating and 60wt% fine WC/NiCu composite coating were prepared on A3 steel by laser melting deposition (LMD). The microstructure was characterized by scanning electron microscope, X-ray spectrometer and optical microscope. The microhardness and wear resistance of the coating were measured by microhardness tester and wear tester. The electrochemical corrosion resistance of NiCu alloy coating and composite coating were tested and analyzed by electrochemical workstation. The results show that the three coatings have formed a good metallurgical bond with the substrate, without obvious cracks and pores under the suitable parameters. The microstructures of cladding layer are mainly equiaxial and columnar, and the size of the grains is obviously reduced by the addition of WC. Compared with the NiCu coating, the microhardness of the coating with 60wt% coarse WC and fine WC increase by 62.1% and 81.1%, respectively, and the wear loss decrease by 84.8% and 94.3%, respectively. The wear mechanism is mainly abrasive wear. In 3.5wt%NaCl solution, the self-corrosion current density of the composite coating is 61% and 49% lower than that of NiCu alloy coating, respectively. The addition of WC significantly improves the performance of the NiCu alloy coating. The fine WC has a more obvious effect on the improvement of microhardness and wear resistance, and the coarse WC has an obvious improvement on the electrochemical corrosion performance.
2022, 39(7): 3510-3517.
doi: 10.13801/j.cnki.fhclxb.20210817.001
Abstract:
Based on slurry extrusion, direct-ink-writing (DIW), which is a simple and cost-effective 3D printing technology, enables the manufacturing of parts with fine and complex three-dimensional architecture under a mild condition. Accordingly, it has great potential and opportunities in the field of advanced ceramic preparation. However, DIW is currently facing problems such as lack of materials and difficulty in the preparation of suitable slurry, hindering its practical and commercial applications. In view of this, a new type of DIW 3D printer based on air pressure was developed in this work. On this basis, a titanium dioxide (TiO2) ceramic slurry suitable for direct writing molding was prepared by using TiO2 as raw material and polyvinyl alcohol (PVA) as a flow aid as well as a binder. The effect of PVA contents on the rheological behavior of the slurry and the DIW printability was systematically studied. Subsequently, TiO2 parts with complex shapes and structures were constructed successfully. The cross-sectional morphologies, printing accuracy as well as the shrinkage of the as-printed parts after sintering was further investigated. The results show that PVA can effectively reduce the viscosity of the slurry and improve its fluidity, which is beneficial to improve the 3D printability, and promote the adhesion between adjacent layers of the printed part. However, ceramic slurry with PVA content above 10wt% could suffer from slump during the deposition stage. With the increasing PVA content, the vickers hardness of the sintered parts decreases, and the shrinkage of the as-prepared parts increases.
Based on slurry extrusion, direct-ink-writing (DIW), which is a simple and cost-effective 3D printing technology, enables the manufacturing of parts with fine and complex three-dimensional architecture under a mild condition. Accordingly, it has great potential and opportunities in the field of advanced ceramic preparation. However, DIW is currently facing problems such as lack of materials and difficulty in the preparation of suitable slurry, hindering its practical and commercial applications. In view of this, a new type of DIW 3D printer based on air pressure was developed in this work. On this basis, a titanium dioxide (TiO2) ceramic slurry suitable for direct writing molding was prepared by using TiO2 as raw material and polyvinyl alcohol (PVA) as a flow aid as well as a binder. The effect of PVA contents on the rheological behavior of the slurry and the DIW printability was systematically studied. Subsequently, TiO2 parts with complex shapes and structures were constructed successfully. The cross-sectional morphologies, printing accuracy as well as the shrinkage of the as-printed parts after sintering was further investigated. The results show that PVA can effectively reduce the viscosity of the slurry and improve its fluidity, which is beneficial to improve the 3D printability, and promote the adhesion between adjacent layers of the printed part. However, ceramic slurry with PVA content above 10wt% could suffer from slump during the deposition stage. With the increasing PVA content, the vickers hardness of the sintered parts decreases, and the shrinkage of the as-prepared parts increases.
2022, 39(7): 3518-3529.
doi: 10.13801/j.cnki.fhclxb.20210716.004
Abstract:
The electrical and processing properties of AgSnO2 composite contact materials were improved by doping. Based on the first principles of density functional theory, the elastic constants of SnO2 supercells doped with Cr-Y and Cr-Ce were calculated by simulation, and the rare earth element Y with better mechanical properties was selected for simulation and experiment of electrical properties. The effects of Cr and Y doping on the electrical properties of SnO2 were analyzed from the energy band structure and density of states. The results show that the band gap of SnO2 decreases and the energy required for electron transition cuts down after doping. The doped SnO2 powder was prepared by sol-gel method, and its phase structure was analyzed by XRD. It is verified that doping ions enter into the SnO2 lattice to form solid solution, and achieves the alternative doping model established by simulation. The doped AgSnO2 composite contact materials were prepared by powder metallurgy method, and their densities, hardnesses and conductivities were measured. The conductivities of doped AgSnO2 contact materials are improved, and Cr-Y co-doped is the best among them, which verifies the simulation results. JF04D type electrical contact material test system was used to test the electrical contact performance of contact materials. The test results show that doping Cr and Y can effectively reduce the arc energy of AgSnO2 contact materials, improve the arc erosion resistance, inhibit the arc ablation of contact materials, and stabilize the arc erosion resistance and welding resistance of contact materials.
The electrical and processing properties of AgSnO2 composite contact materials were improved by doping. Based on the first principles of density functional theory, the elastic constants of SnO2 supercells doped with Cr-Y and Cr-Ce were calculated by simulation, and the rare earth element Y with better mechanical properties was selected for simulation and experiment of electrical properties. The effects of Cr and Y doping on the electrical properties of SnO2 were analyzed from the energy band structure and density of states. The results show that the band gap of SnO2 decreases and the energy required for electron transition cuts down after doping. The doped SnO2 powder was prepared by sol-gel method, and its phase structure was analyzed by XRD. It is verified that doping ions enter into the SnO2 lattice to form solid solution, and achieves the alternative doping model established by simulation. The doped AgSnO2 composite contact materials were prepared by powder metallurgy method, and their densities, hardnesses and conductivities were measured. The conductivities of doped AgSnO2 contact materials are improved, and Cr-Y co-doped is the best among them, which verifies the simulation results. JF04D type electrical contact material test system was used to test the electrical contact performance of contact materials. The test results show that doping Cr and Y can effectively reduce the arc energy of AgSnO2 contact materials, improve the arc erosion resistance, inhibit the arc ablation of contact materials, and stabilize the arc erosion resistance and welding resistance of contact materials.
2022, 39(7): 3530-3541.
doi: 10.13801/j.cnki.fhclxb.20210820.004
Abstract:
In the actual operation process, the surface of brittle carbon fiber layer of carbon fiber reinforced polymer (CFRP)-steel layered structure suffered from scratch and other damage. Therefore, it is necessary to study the damage tolerance to ensure the safe operation of the damaged composite structure. An analytical model of fracture strength at the three-point bending (3-p-b) test for CFRP-steel laminated structure with surface scratch damage was established based on the boundary effect model (BEM). And the initial scratch defects of 0.2 mm and 0.4 mm depth were prefabricated on the surface of CFRP, respectively. The feasibility of this theoretical model was verified at the 3-p-b tests. The results indicate that: (1) The fracture characteristics of CFRP-steel laminated structure at the 3-p-b tests were observed by metallographic microscope, and the structural characteristic parameter Cch of CFRP after scratch damage was determined. The tensile strength of CFRP layer was carried out according to this analytical model, and the deviation is less than 10% compared with the tensile strength measured by CFRP direct tensile test. (2) The analytical model is a linear equation of “fracture load = tensile strength × equivalent area”. The “equivalent area” is only related to CFRP-steel laminated structure and the geometric parameters of surface crack. Therefore, the fracture strength of CFRP-steel laminated structure with surface damage can be predicted by the direct tensile strength of CFRP, and the damage tolerance design can be realized.
In the actual operation process, the surface of brittle carbon fiber layer of carbon fiber reinforced polymer (CFRP)-steel layered structure suffered from scratch and other damage. Therefore, it is necessary to study the damage tolerance to ensure the safe operation of the damaged composite structure. An analytical model of fracture strength at the three-point bending (3-p-b) test for CFRP-steel laminated structure with surface scratch damage was established based on the boundary effect model (BEM). And the initial scratch defects of 0.2 mm and 0.4 mm depth were prefabricated on the surface of CFRP, respectively. The feasibility of this theoretical model was verified at the 3-p-b tests. The results indicate that: (1) The fracture characteristics of CFRP-steel laminated structure at the 3-p-b tests were observed by metallographic microscope, and the structural characteristic parameter Cch of CFRP after scratch damage was determined. The tensile strength of CFRP layer was carried out according to this analytical model, and the deviation is less than 10% compared with the tensile strength measured by CFRP direct tensile test. (2) The analytical model is a linear equation of “fracture load = tensile strength × equivalent area”. The “equivalent area” is only related to CFRP-steel laminated structure and the geometric parameters of surface crack. Therefore, the fracture strength of CFRP-steel laminated structure with surface damage can be predicted by the direct tensile strength of CFRP, and the damage tolerance design can be realized.
2022, 39(7): 3542-3553.
doi: 10.13801/j.cnki.fhclxb.20210905.002
Abstract:
Light weight thermal insulation materials have been widely used in the thermal protection system of aircraft power plant, but the existing technology is difficult to achieve the synergy of many technical goals such as high load, light weight and thermal insulation. In this paper, a kind of lightweight, high strength and low thermal conductivity silicon carbide/graphite composite was rapidly prepared based on the principle of micro-hot pressing additive manufacturing and forming technology. The variation law of compressive strength and thermal conductivity of composite materials under different forming densities was studied. By changing the material formula composition (including thermosetting phenolic resin powder, high purity silicon powder and expandable graphite, etc.), the compressive strength and thermal conductivity of composite materials were adjusted forward and backward, and its internal mechanism was revealed. This research finds that when the mass fraction of phenolic resin powder, high purity silicon powder and expandable graphite is 30wt%, 30wt% and 2wt%, respectively, the silicon carbide/graphite thermal insulation composite has the properties of low density (<1.2 g/cm3), high compressive strength (>15 MPa) and low thermal conductivity (< 1 W/(m·K)), which has a good application prospect in aerospace.
Light weight thermal insulation materials have been widely used in the thermal protection system of aircraft power plant, but the existing technology is difficult to achieve the synergy of many technical goals such as high load, light weight and thermal insulation. In this paper, a kind of lightweight, high strength and low thermal conductivity silicon carbide/graphite composite was rapidly prepared based on the principle of micro-hot pressing additive manufacturing and forming technology. The variation law of compressive strength and thermal conductivity of composite materials under different forming densities was studied. By changing the material formula composition (including thermosetting phenolic resin powder, high purity silicon powder and expandable graphite, etc.), the compressive strength and thermal conductivity of composite materials were adjusted forward and backward, and its internal mechanism was revealed. This research finds that when the mass fraction of phenolic resin powder, high purity silicon powder and expandable graphite is 30wt%, 30wt% and 2wt%, respectively, the silicon carbide/graphite thermal insulation composite has the properties of low density (<1.2 g/cm3), high compressive strength (>15 MPa) and low thermal conductivity (< 1 W/(m·K)), which has a good application prospect in aerospace.
2022, 39(7): 3554-3563.
doi: 10.13801/j.cnki.fhclxb.20211020.001
Abstract:
Ceramic-reinforced aluminum-based composites are ideal materials for lightweight structural parts. However, as the content of the ceramic reinforcement phase increases, the toughness of the composites will decrease, resulting in a decrease in the safety of the composites during service. Therefore, how to achieve the matching of high strength and toughness of composite materials is a problem that has always existed in the preparation of ceramic reinforced aluminum matrix composites. According to the idea of bionics, the nacre-inspired TiB2/Al-Cu composites with different ceramic initial solid contents (20vol%, 30vol%, 40vol%) were successfully prepared by freezing casting and pressure infiltration. The microstructures and mechanical properties of nacre-inspired TiB2/Al-Cu composites were studied by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and mechanical testing. The experimental results show that with the increase of the initial solid content of the ceramic, the thickness of the ceramic sheet in the composite material increases, while the thickness of the metal sheet layer decreases. The compressive strength of the composite material is improved, but the bending strength and fracture toughness decrease. The nacre-inspired TiB2/Al-Cu composites with 20vol% ceramic initial solid content has the better fracture toughness, reaching (20.59±1.5) MPa·m1/2. The nacre-inspired TiB2/Al-Cu composites with 40vol% ceramic initial solid content has the better compressive strength, reaching (670±20) MPa. This is mainly because as the initial solid content of the ceramic in the composite material increases, the nacre-inspired composite material are more prone to interface delamination, the toughening effect of the layered composite material through alloy plastic deformation is weakened. At the same time, the toughening effect of crack deflection, interface peeling, and crack branching is reduced.
Ceramic-reinforced aluminum-based composites are ideal materials for lightweight structural parts. However, as the content of the ceramic reinforcement phase increases, the toughness of the composites will decrease, resulting in a decrease in the safety of the composites during service. Therefore, how to achieve the matching of high strength and toughness of composite materials is a problem that has always existed in the preparation of ceramic reinforced aluminum matrix composites. According to the idea of bionics, the nacre-inspired TiB2/Al-Cu composites with different ceramic initial solid contents (20vol%, 30vol%, 40vol%) were successfully prepared by freezing casting and pressure infiltration. The microstructures and mechanical properties of nacre-inspired TiB2/Al-Cu composites were studied by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and mechanical testing. The experimental results show that with the increase of the initial solid content of the ceramic, the thickness of the ceramic sheet in the composite material increases, while the thickness of the metal sheet layer decreases. The compressive strength of the composite material is improved, but the bending strength and fracture toughness decrease. The nacre-inspired TiB2/Al-Cu composites with 20vol% ceramic initial solid content has the better fracture toughness, reaching (20.59±1.5) MPa·m1/2. The nacre-inspired TiB2/Al-Cu composites with 40vol% ceramic initial solid content has the better compressive strength, reaching (670±20) MPa. This is mainly because as the initial solid content of the ceramic in the composite material increases, the nacre-inspired composite material are more prone to interface delamination, the toughening effect of the layered composite material through alloy plastic deformation is weakened. At the same time, the toughening effect of crack deflection, interface peeling, and crack branching is reduced.
Fabrication, microstructure and mechanical properties of (Me1/3Hf1/3Nb1/3)B2(Me=Ti, Zr, Ta) ceramics
2022, 39(7): 3564-3569.
doi: 10.13801/j.cnki.fhclxb.20210906.002
Abstract:
With (Me1/3Hf1/3Nb1/3)B2 (Me=Ti, Zr, Ta) powders self-synthesized via boron/carbothermal reduction, (Me1/3Hf1/3Nb1/3)B2 ceramics were prepared by spark plasma sintering (SPS), and their phase composition, relative density, microstructure and mechanical properties were investigated systematically. The result reveals that (Ti1/3Hf1/3Nb1/3)B2 and (Zr1/3Hf1/3Nb1/3)B2 possess the high relative density (~98%), while (Ta1/3Hf1/3Nb1/3)B2 has the lowest relative density (~93%). (Ti1/3Hf1/3Nb1/3)B2 possesses relatively coarse grains, while (Zr1/3Hf1/3Nb1/3)B2 and (Ta1/3Hf1/3Nb1/3)B2 possess relatively fine grains and Nb segregation is found in (Ta1/3Hf1/3Nb1/3)B2. (Ti1/3Hf1/3Nb1/3)B2 shows the most excellent mechanical properties with the Vickers hardness and fracture toughness of (20.08±0.81) GPa and (2.52±0.15) MPa·m1/2, respectively, whereas the mechanical properties of (Zr1/3Hf1/3Nb1/3)B2 are inferior, with hardness and fracture toughness of (17.21±0.63) GPa and (1.50±0.18) MPa·m1/2, respectively.
With (Me1/3Hf1/3Nb1/3)B2 (Me=Ti, Zr, Ta) powders self-synthesized via boron/carbothermal reduction, (Me1/3Hf1/3Nb1/3)B2 ceramics were prepared by spark plasma sintering (SPS), and their phase composition, relative density, microstructure and mechanical properties were investigated systematically. The result reveals that (Ti1/3Hf1/3Nb1/3)B2 and (Zr1/3Hf1/3Nb1/3)B2 possess the high relative density (~98%), while (Ta1/3Hf1/3Nb1/3)B2 has the lowest relative density (~93%). (Ti1/3Hf1/3Nb1/3)B2 possesses relatively coarse grains, while (Zr1/3Hf1/3Nb1/3)B2 and (Ta1/3Hf1/3Nb1/3)B2 possess relatively fine grains and Nb segregation is found in (Ta1/3Hf1/3Nb1/3)B2. (Ti1/3Hf1/3Nb1/3)B2 shows the most excellent mechanical properties with the Vickers hardness and fracture toughness of (20.08±0.81) GPa and (2.52±0.15) MPa·m1/2, respectively, whereas the mechanical properties of (Zr1/3Hf1/3Nb1/3)B2 are inferior, with hardness and fracture toughness of (17.21±0.63) GPa and (1.50±0.18) MPa·m1/2, respectively.
2022, 39(7): 3570-3580.
doi: 10.13801/j.cnki.fhclxb.20210729.003
Abstract:
In this paper, a variable arc concave honeycomb structure with negative Poisson’s ratio was proposed. The analytical formulas of the equivalent Poisson’s ratio and the equivalent elastic modulus of the two-dimensional structures were given by energy method. The influences of the arc angle on the equivalent Poisson’s ratio and the equivalent elastic modulus were discussed. The present analytical solution is in agreement with the finite element results, which shows validity of the present method. The three-dimensional structures’ characteristics of the dynamic were studied by ABAQUS, and the deformation failure mode of the whole honeycomb structures under impact was analyzed. The influences of the impact velocity, structural strain and arc angle on the dynamic stress-strain curve, the energy absorption rate and the platform stress were discussed. The results provide a mechanical basis for the analysis of impact deformation failure and energy absorption effect of such mechanical metamaterials.
In this paper, a variable arc concave honeycomb structure with negative Poisson’s ratio was proposed. The analytical formulas of the equivalent Poisson’s ratio and the equivalent elastic modulus of the two-dimensional structures were given by energy method. The influences of the arc angle on the equivalent Poisson’s ratio and the equivalent elastic modulus were discussed. The present analytical solution is in agreement with the finite element results, which shows validity of the present method. The three-dimensional structures’ characteristics of the dynamic were studied by ABAQUS, and the deformation failure mode of the whole honeycomb structures under impact was analyzed. The influences of the impact velocity, structural strain and arc angle on the dynamic stress-strain curve, the energy absorption rate and the platform stress were discussed. The results provide a mechanical basis for the analysis of impact deformation failure and energy absorption effect of such mechanical metamaterials.
2022, 39(7): 3581-3589.
doi: 10.13801/j.cnki.fhclxb.20210806.001
Abstract:
As preferred high-temperature structural materials for the next generation aerospace craft, carbon fiber reinforced thermoplastic polyether ether ketone composite (CF/PEEK) has excellent properties, such as high impact resistance, repairability, high temperature resistance and so forth. Because of the crystallization characteristics, the PEEK matrix still has a high load-carrying capacity above the glass transition temperature (around 143℃), and therefore CF/PEEK composite can be used under long term operation at 200℃. However, due to the wide forming temperature range and service temperature range of CF/PEEK composites, PEEK resin will gradually relax at high temperature. Consequently, CF/PEEK composites will show obvious time-, temperature-, and loading history-dependent anisotropic viscoelasticity, which make it very hard to accurately design the forming history and service history of the composite structures. Currently, the existing high temperature prediction model of composites is usually based on the elastic-plastic constitutive stiffness reduction method, which does not fully consider the anisotropic relaxation behavior of the composites. An anisotropic viscoelastic constitutive model was developed to describe the time- and temperature- dependent properties of composites. The generalized Maxwell viscoelastic parameters of the PEEK resin were obtained by characterizing the relaxation modulus main curve in a wide temperature range (25~200℃). Then, by semi-empirical solution for equivalent mechanical properties of composite materials, a three-dimensional anisotropic constitutive model was developed. Finally, the developed model has been verified by comparing with the high temperature relaxation experiments and the finite element simulation by the representative volume element (RVE) along the transverse direction. Overall, the developed model can be used to simulate the forming process and design the high temperature mechanical properties of CF/PEEK composites.
As preferred high-temperature structural materials for the next generation aerospace craft, carbon fiber reinforced thermoplastic polyether ether ketone composite (CF/PEEK) has excellent properties, such as high impact resistance, repairability, high temperature resistance and so forth. Because of the crystallization characteristics, the PEEK matrix still has a high load-carrying capacity above the glass transition temperature (around 143℃), and therefore CF/PEEK composite can be used under long term operation at 200℃. However, due to the wide forming temperature range and service temperature range of CF/PEEK composites, PEEK resin will gradually relax at high temperature. Consequently, CF/PEEK composites will show obvious time-, temperature-, and loading history-dependent anisotropic viscoelasticity, which make it very hard to accurately design the forming history and service history of the composite structures. Currently, the existing high temperature prediction model of composites is usually based on the elastic-plastic constitutive stiffness reduction method, which does not fully consider the anisotropic relaxation behavior of the composites. An anisotropic viscoelastic constitutive model was developed to describe the time- and temperature- dependent properties of composites. The generalized Maxwell viscoelastic parameters of the PEEK resin were obtained by characterizing the relaxation modulus main curve in a wide temperature range (25~200℃). Then, by semi-empirical solution for equivalent mechanical properties of composite materials, a three-dimensional anisotropic constitutive model was developed. Finally, the developed model has been verified by comparing with the high temperature relaxation experiments and the finite element simulation by the representative volume element (RVE) along the transverse direction. Overall, the developed model can be used to simulate the forming process and design the high temperature mechanical properties of CF/PEEK composites.
2022, 39(7): 3590-3602.
doi: 10.13801/j.cnki.fhclxb.20210903.001
Abstract:
Various defects with dispersive feature sizes can be accumulated inevitably in fiber-reinforced resin composites during their manufacturing and service processes, which are also difficult to be detected. The final objective of defects testing is to obtain the accuracy assessment of performance of defective structures. A micro-stress non-destructive defect detection and evaluation method is proposed for fiber-reinforced resin composites, which is especially suitable for composites measurement. Combing with the optical measurement technology for full-field displacement, the abnormal responses which caused by the defects of the structure under low stress level is able to be captured. The wrinkle defect detection is taken as an example to show the measurement processes. First, a specific detection scheme is designed based on the theoretical prediction of characteristic responses of wrinkles. Then, a new method of full-field displacement measurement is innovatively proposed based on the grating projection technology. Results show that under the axial tensile loading, the distorted out-of-plane displacements caused by wrinkles can be detected by the improved grating projection technology. The distorted displacements revealed the spatial distribution and severity of defects, and the influence on structural performance degradation can be evaluated based on the degree of displacement distortion. Further, by applying the optical-mechanical detection method, the mechanical responses of the defective component under a given working condition can be obtained directly, which can provide a reference for the adaptability evaluation of the component.
Various defects with dispersive feature sizes can be accumulated inevitably in fiber-reinforced resin composites during their manufacturing and service processes, which are also difficult to be detected. The final objective of defects testing is to obtain the accuracy assessment of performance of defective structures. A micro-stress non-destructive defect detection and evaluation method is proposed for fiber-reinforced resin composites, which is especially suitable for composites measurement. Combing with the optical measurement technology for full-field displacement, the abnormal responses which caused by the defects of the structure under low stress level is able to be captured. The wrinkle defect detection is taken as an example to show the measurement processes. First, a specific detection scheme is designed based on the theoretical prediction of characteristic responses of wrinkles. Then, a new method of full-field displacement measurement is innovatively proposed based on the grating projection technology. Results show that under the axial tensile loading, the distorted out-of-plane displacements caused by wrinkles can be detected by the improved grating projection technology. The distorted displacements revealed the spatial distribution and severity of defects, and the influence on structural performance degradation can be evaluated based on the degree of displacement distortion. Further, by applying the optical-mechanical detection method, the mechanical responses of the defective component under a given working condition can be obtained directly, which can provide a reference for the adaptability evaluation of the component.
2022, 39(7): 3603-3615.
doi: 10.13801/j.cnki.fhclxb.20210805.001
Abstract:
Based on extended layerwise method (XLWM), discrete damage zone model (DDZM) and Peerlings damage law, a fatigue progressive extended layerwise method (FPXLWM) was established to analyze the delamination fatigue growth of composites. Firstly, a HTC/6736A carbon fiber double cantilever beam subjected to a constant bending moment was analyzed to verify the proposed method in numerical examples. Then, the fatigue parameters of the proposed model were determined by several groups of Paris curves; the fatigue growth mechanisms of delamination in the HTC/6736A carbon fiber double cantilever beam were investigated.
Based on extended layerwise method (XLWM), discrete damage zone model (DDZM) and Peerlings damage law, a fatigue progressive extended layerwise method (FPXLWM) was established to analyze the delamination fatigue growth of composites. Firstly, a HTC/6736A carbon fiber double cantilever beam subjected to a constant bending moment was analyzed to verify the proposed method in numerical examples. Then, the fatigue parameters of the proposed model were determined by several groups of Paris curves; the fatigue growth mechanisms of delamination in the HTC/6736A carbon fiber double cantilever beam were investigated.
2022, 39(7): 3616-3628.
doi: 10.13801/j.cnki.fhclxb.20210819.004
Abstract:
The hydrostatic tests for the Ф1
The hydrostatic tests for the Ф1
2022, 39(7): 3629-3640.
doi: 10.13801/j.cnki.fhclxb.20210823.002
Abstract:
Although the new combat helmet can effectively reduce the pistol bullet penetrating damage, the back face deformation (BFD) of helmet may cause head injury. In order to accurately simulate the transient mechanical response of combat helmet under bullet impact, a progressive damage constitutive model for simulating the mechanical properties of composite combat helmet was developed based on the user material subroutine VUMAT of Abaqus. The finite element model of 9 mm lead core pistol bullet penetrating PASGT aramid combat helmet with impacting velocity 343 m/s was established. The accuracy of the numerical simulation was verified by the helmet BFD curve and the bulge shape of the inner surface. The failure mode of combat helmet shows that the helmet mainly occurs fiber tension, matrix compression and delamination failure. During the penetrating process, the stress contours on the helmet presents a regular diamond shape at the initial stage, and then slowly diffuses around and evolves into a circle. At three different angles of incidence (30°, 45°, 60°), the velocity of rebound is 72.9 m/s, 165.5 m/s and 240.1 m/s, respectively. Finally, the probability of skull fracture caused by the BFD of the helmet was estimated using the blunt criterion.
Although the new combat helmet can effectively reduce the pistol bullet penetrating damage, the back face deformation (BFD) of helmet may cause head injury. In order to accurately simulate the transient mechanical response of combat helmet under bullet impact, a progressive damage constitutive model for simulating the mechanical properties of composite combat helmet was developed based on the user material subroutine VUMAT of Abaqus. The finite element model of 9 mm lead core pistol bullet penetrating PASGT aramid combat helmet with impacting velocity 343 m/s was established. The accuracy of the numerical simulation was verified by the helmet BFD curve and the bulge shape of the inner surface. The failure mode of combat helmet shows that the helmet mainly occurs fiber tension, matrix compression and delamination failure. During the penetrating process, the stress contours on the helmet presents a regular diamond shape at the initial stage, and then slowly diffuses around and evolves into a circle. At three different angles of incidence (30°, 45°, 60°), the velocity of rebound is 72.9 m/s, 165.5 m/s and 240.1 m/s, respectively. Finally, the probability of skull fracture caused by the BFD of the helmet was estimated using the blunt criterion.
2022, 39(7): 3641-3651.
doi: 10.13801/j.cnki.fhclxb.20210903.005
Abstract:
The local impact dynamic characteristics of X-type lattice sandwich structure were studied by using the drop weight impact test, and the effects of different parameters on the impact performance were analyzed. The results show that the impact failure process roughly goes through four typical stages: The overall bearing force stage, the upper panel failure stage, the lower panel stress strengthening stage and the lower panel failure stage. The impact velocity and panel thickness have great effects on the impact peak load and energy absorption of the X-type lattice sandwich structure. The core thickness has little effect on the impact peak load and energy absorption of X-shaped lattice sandwich structure, while the core angle has a certain effect on the impact peak load and energy absorption of X-shaped lattice sandwich structure. The local impact dynamic behavior of the X-type lattice sandwich structure was numerically simulated by finite element method. The reliability of the finite element model was verified by the comparative analysis of failure modes and force-time curves.
The local impact dynamic characteristics of X-type lattice sandwich structure were studied by using the drop weight impact test, and the effects of different parameters on the impact performance were analyzed. The results show that the impact failure process roughly goes through four typical stages: The overall bearing force stage, the upper panel failure stage, the lower panel stress strengthening stage and the lower panel failure stage. The impact velocity and panel thickness have great effects on the impact peak load and energy absorption of the X-type lattice sandwich structure. The core thickness has little effect on the impact peak load and energy absorption of X-shaped lattice sandwich structure, while the core angle has a certain effect on the impact peak load and energy absorption of X-shaped lattice sandwich structure. The local impact dynamic behavior of the X-type lattice sandwich structure was numerically simulated by finite element method. The reliability of the finite element model was verified by the comparative analysis of failure modes and force-time curves.
2022, 39(7): 3652-3662.
doi: 10.13801/j.cnki.fhclxb.20210819.006
Abstract:
Graphene, as a new type of reinforcement material, has a wide application prospect in strengthening the mechanical properties of metals. The indentation response of single crystal aluminum (Al) and aluminum coated by single or double-layer graphene (Gr/Al) was calculated by molecular dynamics method. The indentation properties of Al and Gr/Al under the spherical indenter were studied, and the indentation mechanical behaviors were analyzed to investigate the influence of Gr coating on Al matrix properties under indentation. The results show that the Gr coating can significantly enhance the bearing capacity of Al matrix, and improve the hardness and reduced elastic modulus of Al matrix. Through the analysis of deformation behavior, internal stress and dislocation expansion, it is found that there are two main reasons for Gr to improve the indentation performance of Al matrix: one is the increase of bearing area of Al matrix under the "lifting action" of Gr coating. The second is that Gr coating changes the dislocation expansion in Al matrix. By comparing the indentation properties of Al matrix under single and double Gr coating, it is found that increasing Gr layer number can improve the bearing capacity of the whole system, but reduce the critical depth of the system.
Graphene, as a new type of reinforcement material, has a wide application prospect in strengthening the mechanical properties of metals. The indentation response of single crystal aluminum (Al) and aluminum coated by single or double-layer graphene (Gr/Al) was calculated by molecular dynamics method. The indentation properties of Al and Gr/Al under the spherical indenter were studied, and the indentation mechanical behaviors were analyzed to investigate the influence of Gr coating on Al matrix properties under indentation. The results show that the Gr coating can significantly enhance the bearing capacity of Al matrix, and improve the hardness and reduced elastic modulus of Al matrix. Through the analysis of deformation behavior, internal stress and dislocation expansion, it is found that there are two main reasons for Gr to improve the indentation performance of Al matrix: one is the increase of bearing area of Al matrix under the "lifting action" of Gr coating. The second is that Gr coating changes the dislocation expansion in Al matrix. By comparing the indentation properties of Al matrix under single and double Gr coating, it is found that increasing Gr layer number can improve the bearing capacity of the whole system, but reduce the critical depth of the system.
