2022 Vol. 39, No. 2
2022, 39(2): 431-445.
doi: 10.13801/j.cnki.fhclxb.20210828.001
Abstract:
Fiber reinforced polymer composites are widely used in the fields of aeronautics, astronautics and marine technology engineering. Long-term cyclic load in hygrothermal environment is a critical problem for composite structural design and analysis, which has a significant impact on the strength and stiffness of composite structures. In the present review, by introducing moisture absorption model, performance degeneration of composites under hygrothermal environment was described. Following that, the review focused on the fatigue properties of composites under hygrothermal environment. The hygrothermal factors affecting the fatigue performance of fiber reinforced polymer composites were reviewed. The challenges and the existing problems were summarized. The future development of fiber reinforced polymer composites was finally discussed.
Fiber reinforced polymer composites are widely used in the fields of aeronautics, astronautics and marine technology engineering. Long-term cyclic load in hygrothermal environment is a critical problem for composite structural design and analysis, which has a significant impact on the strength and stiffness of composite structures. In the present review, by introducing moisture absorption model, performance degeneration of composites under hygrothermal environment was described. Following that, the review focused on the fatigue properties of composites under hygrothermal environment. The hygrothermal factors affecting the fatigue performance of fiber reinforced polymer composites were reviewed. The challenges and the existing problems were summarized. The future development of fiber reinforced polymer composites was finally discussed.
2022, 39(2): 446-459.
doi: 10.13801/j.cnki.fhclxb.20210824.002
Abstract:
Carbon fiber reinforced polymer (CFRP) has been widely used in robotics, aerospace, engineering equipment and other fields for its advantages of thermal shock resistance, high tensile strength and corrosion resistance. Producing hydraulic cylinder with CFRP can greatly improve the lightweight level of hydraulic system and reduce energy consumption further. The paper summarizes the development status of CFRP hydraulic cylinder from five aspects: composite cylinder, piston and piston rod, molding process, sealing and lubrication, and development trends. Then the connection methods between metal and composite material in cylinder and piston are introduced, during which the reference criteria of multi-material design is given in detail. The processing technologies of hand lay-up, filament winding, pultrusion, resin transfer model forming are shown, then the problems of sealing, friction and dynamic response of CFRP hydraulic cylinder are discussed. Finally, the development trends of CFRP hydraulic cylinder are given from three aspects: Coating, processing and post-treatment.
Carbon fiber reinforced polymer (CFRP) has been widely used in robotics, aerospace, engineering equipment and other fields for its advantages of thermal shock resistance, high tensile strength and corrosion resistance. Producing hydraulic cylinder with CFRP can greatly improve the lightweight level of hydraulic system and reduce energy consumption further. The paper summarizes the development status of CFRP hydraulic cylinder from five aspects: composite cylinder, piston and piston rod, molding process, sealing and lubrication, and development trends. Then the connection methods between metal and composite material in cylinder and piston are introduced, during which the reference criteria of multi-material design is given in detail. The processing technologies of hand lay-up, filament winding, pultrusion, resin transfer model forming are shown, then the problems of sealing, friction and dynamic response of CFRP hydraulic cylinder are discussed. Finally, the development trends of CFRP hydraulic cylinder are given from three aspects: Coating, processing and post-treatment.
2022, 39(2): 460-466.
doi: 10.13801/j.cnki.fhclxb.20210805.005
Abstract:
Layered transition metal carbonitride (MXene) is a new type of two-dimensional nanomaterials. It has attracted increasing attention due to its unique crystal characteristics and structural characteristics, especially its excellent performance in electrical and electronic applications. In recent years, there have been many studies on the composite applications of MXene and textile materials, their outstanding performance have been found in the applications of fiber-based flexible electronics. This paper introduced the preparation approaches and properties of MXene nanosheets, systematically analyzed the latest research of the composite application of MXene and fibrous materials at different dimensions and then summarized the application performance of MXene-based fibrous composite materials. Finally, the cutting-edge research and current challenges of composite applications of MXene and fibrous materials were discussed.
Layered transition metal carbonitride (MXene) is a new type of two-dimensional nanomaterials. It has attracted increasing attention due to its unique crystal characteristics and structural characteristics, especially its excellent performance in electrical and electronic applications. In recent years, there have been many studies on the composite applications of MXene and textile materials, their outstanding performance have been found in the applications of fiber-based flexible electronics. This paper introduced the preparation approaches and properties of MXene nanosheets, systematically analyzed the latest research of the composite application of MXene and fibrous materials at different dimensions and then summarized the application performance of MXene-based fibrous composite materials. Finally, the cutting-edge research and current challenges of composite applications of MXene and fibrous materials were discussed.
2022, 39(2): 467-477.
doi: 10.13801/j.cnki.fhclxb.20210729.001
Abstract:
Ti3C2T
Ti3C2T
2022, 39(2): 478-488.
doi: 10.13801/j.cnki.fhclxb.20210714.001
Abstract:
Monitoring the volatile organic compounds (VOCs) is an important part in the environmental governance. However, it is still a great challenge to develop rapid and high-sensitive detecting system for VOCs detection. The VOCs sensor based on sensing materials can achieve the real-time monitoring of the concentration of pollutants in the air. Therefore, the emission standard of VOCs can be adjusted to reduce the harm of VOCs to human body and environment. Sensitive elements with the performance of repaid identification and capture of VOCs, can be accomplished by controlling materials and methods. And hence the gas sensor with superior sensitivity, safety and reliability can be obtained. This paper extensively reviewed the research progress of VOCs-sensing films prepared with the materials of polymers, metallic oxides, composites and novel materials, focusing the attention on the mechanisms of interaction between VOCs and sensing membranes. Furthermore, the construction strategies of sensing materials for improving the sensitivity and detection limit for VOCs detection were discussed. Finally, the prospects and challenges of sensing films with optical effect (e.g. photoluminescent and chiral nematic sensitive films) on the VOCs detection were indicated.
Monitoring the volatile organic compounds (VOCs) is an important part in the environmental governance. However, it is still a great challenge to develop rapid and high-sensitive detecting system for VOCs detection. The VOCs sensor based on sensing materials can achieve the real-time monitoring of the concentration of pollutants in the air. Therefore, the emission standard of VOCs can be adjusted to reduce the harm of VOCs to human body and environment. Sensitive elements with the performance of repaid identification and capture of VOCs, can be accomplished by controlling materials and methods. And hence the gas sensor with superior sensitivity, safety and reliability can be obtained. This paper extensively reviewed the research progress of VOCs-sensing films prepared with the materials of polymers, metallic oxides, composites and novel materials, focusing the attention on the mechanisms of interaction between VOCs and sensing membranes. Furthermore, the construction strategies of sensing materials for improving the sensitivity and detection limit for VOCs detection were discussed. Finally, the prospects and challenges of sensing films with optical effect (e.g. photoluminescent and chiral nematic sensitive films) on the VOCs detection were indicated.
2022, 39(2): 489-501.
doi: 10.13801/j.cnki.fhclxb.20210713.001
Abstract:
The combination of the new-type inorganic nanomaterials with the traditional polymer molecules will greatly promote the fully demonstrate of the versatility and high reinforcing property of the graphene, as well as the good mechanical properties and mature technology of the polymer. The development of the functional materials, nano-graphene and the polymer was briefly described in this paper. The polymer source of adsorption materials (three kinds of natural polymer, synthetic polymer), the application of catalytic materials in (synthetic, electric-) chemical reactions, the pore size characteristics of separation materials (low permeability, nanofiltration, ultrafiltration, microfiltration), and the use (tissue engineering, medical health, and medical materials) of biomedical materials were briefly analyzed. The functions and efficiency of various graphene/polymer functional composites were focused on, and their preparation methods and the reasons for the improvement of efficiency were simply stated. At the same time, the conductive materials, intelligent (or conduction) materials and magnetic materials and liquid crystal materials were summarized. It is expected to provide reference for the development and application of novel graphene/polymer functional composites. Last but not the least, the problems existing in the popularization rate and industrialization of graphene/polymer functional composites were also considered and prospected.
The combination of the new-type inorganic nanomaterials with the traditional polymer molecules will greatly promote the fully demonstrate of the versatility and high reinforcing property of the graphene, as well as the good mechanical properties and mature technology of the polymer. The development of the functional materials, nano-graphene and the polymer was briefly described in this paper. The polymer source of adsorption materials (three kinds of natural polymer, synthetic polymer), the application of catalytic materials in (synthetic, electric-) chemical reactions, the pore size characteristics of separation materials (low permeability, nanofiltration, ultrafiltration, microfiltration), and the use (tissue engineering, medical health, and medical materials) of biomedical materials were briefly analyzed. The functions and efficiency of various graphene/polymer functional composites were focused on, and their preparation methods and the reasons for the improvement of efficiency were simply stated. At the same time, the conductive materials, intelligent (or conduction) materials and magnetic materials and liquid crystal materials were summarized. It is expected to provide reference for the development and application of novel graphene/polymer functional composites. Last but not the least, the problems existing in the popularization rate and industrialization of graphene/polymer functional composites were also considered and prospected.
2022, 39(2): 502-512.
doi: 10.13801/j.cnki.fhclxb.20210621.001
Abstract:
Carbon materials and metal oxides are commonly used heterogeneous catalyst supports. Among them, carbon materials have large specific surface area and good adsorption performance, but have poor mechanical properties. Metal oxide supports have good mechanical and thermal stability, but they usually have a strong interaction with active metals leading to lower catalytic activity. As a new type of material, carbon/metal oxide composites have attracted extensive attention from scientists. Because of the synergistic effect between carbon and metal oxides (such as titania, alumina, etc.), the composites exhibit unique physical and chemical properties different from a single component. In this review, the preparation methods of the composites and the research progress in the field of catalysis in recent years were summarized.
Carbon materials and metal oxides are commonly used heterogeneous catalyst supports. Among them, carbon materials have large specific surface area and good adsorption performance, but have poor mechanical properties. Metal oxide supports have good mechanical and thermal stability, but they usually have a strong interaction with active metals leading to lower catalytic activity. As a new type of material, carbon/metal oxide composites have attracted extensive attention from scientists. Because of the synergistic effect between carbon and metal oxides (such as titania, alumina, etc.), the composites exhibit unique physical and chemical properties different from a single component. In this review, the preparation methods of the composites and the research progress in the field of catalysis in recent years were summarized.
2022, 39(2): 513-527.
doi: 10.13801/j.cnki.fhclxb.20210708.002
Abstract:
Lithium-ion battery (LIB) has received considerable attention in recent years, mainly because LIB has higher energy density, power and efficiency compared with other rechargeable batteries. The cathode material plays an important role in determining the LIB performance (e.g, capacity, thermal stability, and potential) and is the main part of LIB system. This paper presents a systematic classification of LIB cathode materials, including mono-, binary-, and ternary-based lithium metal oxide and lithium iron phosphate cathode materials, and the advantages and disadvantages of these cathode materials are systematically reviewed. The physical properties of commercialized cathode materials are compared and evaluated for potential commercialization. Finally, the advantages and disadvantages of each cathode materials are summarized, and the challenges and prospects of cathode materials for the future application are discussed.
Lithium-ion battery (LIB) has received considerable attention in recent years, mainly because LIB has higher energy density, power and efficiency compared with other rechargeable batteries. The cathode material plays an important role in determining the LIB performance (e.g, capacity, thermal stability, and potential) and is the main part of LIB system. This paper presents a systematic classification of LIB cathode materials, including mono-, binary-, and ternary-based lithium metal oxide and lithium iron phosphate cathode materials, and the advantages and disadvantages of these cathode materials are systematically reviewed. The physical properties of commercialized cathode materials are compared and evaluated for potential commercialization. Finally, the advantages and disadvantages of each cathode materials are summarized, and the challenges and prospects of cathode materials for the future application are discussed.
2022, 39(2): 528-543.
doi: 10.13801/j.cnki.fhclxb.20210805.006
Abstract:
Carbon fiber reinforced epoxy composites (CF/EP) have been widely used in industry due to the excellent mechanical properties, but poor interlaminar property limits the performance advantage. Interleaving toughening is one of the valid methods to solve this problem. With the development of material science and technology, the thermoplastic resin and carbon nanomaterials are successively used in the study of the interleaved composites. The research progress of the interleaved composites by thermoplastic resin, carbon nanomaterials and combination of both was reviewed, and the toughening mechanism of thermoplastic/thermoset dualphase system and its synergy with carbon nanomaterials was analyzed, which provided the guideline and reference for the subsequent research on the interleaved composites.
Carbon fiber reinforced epoxy composites (CF/EP) have been widely used in industry due to the excellent mechanical properties, but poor interlaminar property limits the performance advantage. Interleaving toughening is one of the valid methods to solve this problem. With the development of material science and technology, the thermoplastic resin and carbon nanomaterials are successively used in the study of the interleaved composites. The research progress of the interleaved composites by thermoplastic resin, carbon nanomaterials and combination of both was reviewed, and the toughening mechanism of thermoplastic/thermoset dualphase system and its synergy with carbon nanomaterials was analyzed, which provided the guideline and reference for the subsequent research on the interleaved composites.
2022, 39(2): 544-558.
doi: 10.13801/j.cnki.fhclxb.20210607.001
Abstract:
Polymer/inorganic nanoparticle composite microspheres have excellent comprehensive properties such as good designability, fluidity, thermal stability and functional base surface characteristics. The morphology, particle size, distribution and surface structure of polymer/inorganic nanoparticle composite microspheres can be significantly changed according to the preparation method, which can affect their physical and chemical properties. This article reviews the research progress of emulsion polymerization, suspension polymerization, dispersion polymerization, two-step compounding, self-assembly, physical induction and template-assisted methods in preparing polymer/inorganic nanoparticle composite microspheres. The preparation methods of multi-layer, core-shell and functionalized composite microspheres have also been summarized. Finally, the current problems in the chemical preparation of polymer/inorganic nanoparticle composite microspheres are proposed and prospected.
Polymer/inorganic nanoparticle composite microspheres have excellent comprehensive properties such as good designability, fluidity, thermal stability and functional base surface characteristics. The morphology, particle size, distribution and surface structure of polymer/inorganic nanoparticle composite microspheres can be significantly changed according to the preparation method, which can affect their physical and chemical properties. This article reviews the research progress of emulsion polymerization, suspension polymerization, dispersion polymerization, two-step compounding, self-assembly, physical induction and template-assisted methods in preparing polymer/inorganic nanoparticle composite microspheres. The preparation methods of multi-layer, core-shell and functionalized composite microspheres have also been summarized. Finally, the current problems in the chemical preparation of polymer/inorganic nanoparticle composite microspheres are proposed and prospected.
2022, 39(2): 559-567.
doi: 10.13801/j.cnki.fhclxb.20210526.002
Abstract:
The interface toughening effect and toughening mechanism of low-density aramid staple fiber (AF) on the carbon fiber reinforced epoxy resin composite (CF/EP)-aluminum honeycomb sandwich structure were studied. A composite sandwich beam was prepared, and AF of 6 mm length was made into a thin layer of flocculent fibers for the toughening of the sandwich beam interface layer. The asymmetric double cantilever beam experiment was used to measure the interface fracture toughness of toughened and un-toughened sandwich beams. Compared with the un-toughened sandwich beam specimens, the average critical energy release rate of the toughened specimens is increased by 91%, and the average critical load is increased by 55%. The addition of the AF toughening layer only increases the quality of the sandwich beam by 0.36%, which shows that the method in this paper has a good toughening effect and efficiency. SEM was used to observe the cross-sectional morphology and characteristics of the sandwich beam interface. The microscopic observation results show that during the expansion of the interface crack, the AF forms a bridging microstructure between the panel and the core, and improves the dissipation energy and critical load of interface crack propagation through fiber pull-out, fiber peeling, fiber breakage, etc. On the other hand, in the surplus area of the resin “round corners” around the honeycomb panel, the AF can also improve the bonding performance of the resin and the honeycomb panel, and prevent the honeycomb panel from being pulled out due to the small contact area with the panel. This paper quantitatively measured the macro-toughening effect of AF on the CF/EP-aluminum honeycomb interface, and explained its micro-toughening mechanism. The related findings can provide guidance for improving the safety and reliability of composite sandwich structures.
The interface toughening effect and toughening mechanism of low-density aramid staple fiber (AF) on the carbon fiber reinforced epoxy resin composite (CF/EP)-aluminum honeycomb sandwich structure were studied. A composite sandwich beam was prepared, and AF of 6 mm length was made into a thin layer of flocculent fibers for the toughening of the sandwich beam interface layer. The asymmetric double cantilever beam experiment was used to measure the interface fracture toughness of toughened and un-toughened sandwich beams. Compared with the un-toughened sandwich beam specimens, the average critical energy release rate of the toughened specimens is increased by 91%, and the average critical load is increased by 55%. The addition of the AF toughening layer only increases the quality of the sandwich beam by 0.36%, which shows that the method in this paper has a good toughening effect and efficiency. SEM was used to observe the cross-sectional morphology and characteristics of the sandwich beam interface. The microscopic observation results show that during the expansion of the interface crack, the AF forms a bridging microstructure between the panel and the core, and improves the dissipation energy and critical load of interface crack propagation through fiber pull-out, fiber peeling, fiber breakage, etc. On the other hand, in the surplus area of the resin “round corners” around the honeycomb panel, the AF can also improve the bonding performance of the resin and the honeycomb panel, and prevent the honeycomb panel from being pulled out due to the small contact area with the panel. This paper quantitatively measured the macro-toughening effect of AF on the CF/EP-aluminum honeycomb interface, and explained its micro-toughening mechanism. The related findings can provide guidance for improving the safety and reliability of composite sandwich structures.
2022, 39(2): 568-576.
doi: 10.13801/j.cnki.fhclxb.20210330.005
Abstract:
The phosphomolybdic acid-based ionic liquid (PMAIL) was synthesized by ion-exchange method, and it was compounded to the intumescent flame-retardant thermoplastic polyurethane elastomer (IFR/TPU) compo-sites together with layered double hydroxide (LDH). The effect of PMAIL and LDH on the flame retardant properties, thermal stability and processing fluidity of IFR/TPU composites was investigated. The results show that the combination of PMAIL and LDH improve the flame retardancy and thermal stability of IFR/TPU composites. When the mass ratio of PMAIL, LDH and IFR is 0.2∶1.0∶8.8 and the total addition amount is 10wt%, the limiting oxygen index of the PMAIL-LDH-IFR/TPU composites is increased to 30.1% and the vertical burning test reach UL-94 V-0 rating. Moreover, the peak heat release rate and total heat release of PMAIL-LDH-IFR/TPU sample are reduced by 88.06% and 45.88% respectively compared with that of control TPU. The changes in the results such as the balanced torque, melt index and melting temperature indicate the improvement of processing fluidity for PMAIL-LDH-IFR/TPU composites.
The phosphomolybdic acid-based ionic liquid (PMAIL) was synthesized by ion-exchange method, and it was compounded to the intumescent flame-retardant thermoplastic polyurethane elastomer (IFR/TPU) compo-sites together with layered double hydroxide (LDH). The effect of PMAIL and LDH on the flame retardant properties, thermal stability and processing fluidity of IFR/TPU composites was investigated. The results show that the combination of PMAIL and LDH improve the flame retardancy and thermal stability of IFR/TPU composites. When the mass ratio of PMAIL, LDH and IFR is 0.2∶1.0∶8.8 and the total addition amount is 10wt%, the limiting oxygen index of the PMAIL-LDH-IFR/TPU composites is increased to 30.1% and the vertical burning test reach UL-94 V-0 rating. Moreover, the peak heat release rate and total heat release of PMAIL-LDH-IFR/TPU sample are reduced by 88.06% and 45.88% respectively compared with that of control TPU. The changes in the results such as the balanced torque, melt index and melting temperature indicate the improvement of processing fluidity for PMAIL-LDH-IFR/TPU composites.
2022, 39(2): 577-589.
doi: 10.13801/j.cnki.fhclxb.20210402.001
Abstract:
The elastic properties of the composites with graphene sheets distributed continuously and discontinuously in the epoxy matrix were investigated via sandwich representative volume element (RVE) and embedded RVE, respectively. The RVEs were considered as a three phase composite structure, in which the interphase between graphene and epoxy resin matrix was treated as continuum medium while its material properties were considered to vary uniformly, linearly and exponentially. In the finite element modeling process of the RVE, the graphene was discretized using beam element and the epoxy matrix was discretized via the use of solid element while the interfacial layer was approached using isoparametric graded element (IGE). The finite element software ABAQUS was used to analyze the mechanical deformation behavior of the RVE subjected to small strains and extract its elastic properties. The extracted results of elastic properties were then used to study the effects of interfacial layer properties on the elastic properties of graphene/epoxy composites. The validity of the proposed computational method based on the IGE was verified by comparing with rule of mixture (ROM), the modified Halpin-Tsai model and the experimental data. Numerical examples illustrate that the IGE has the advantages of less computation, fast convergence and high accuracy in dealing with the uneven distribution of material properties in the interfacial layer. The prediction results of Young's modulus of composites reveal that when the material properties of interfacial layer adopt the gradient model, the calculated results of Young's modulus are larger than those of uniform distribution model, ROM and the modified Halpin-Tsai model, but closer to the experimental value. The results of this research show that the property of interfacial layer is an important factor affecting the mechanical properties of composites, and provide an effective way to seek more accurate analysis of the mechanical properties of composites.
The elastic properties of the composites with graphene sheets distributed continuously and discontinuously in the epoxy matrix were investigated via sandwich representative volume element (RVE) and embedded RVE, respectively. The RVEs were considered as a three phase composite structure, in which the interphase between graphene and epoxy resin matrix was treated as continuum medium while its material properties were considered to vary uniformly, linearly and exponentially. In the finite element modeling process of the RVE, the graphene was discretized using beam element and the epoxy matrix was discretized via the use of solid element while the interfacial layer was approached using isoparametric graded element (IGE). The finite element software ABAQUS was used to analyze the mechanical deformation behavior of the RVE subjected to small strains and extract its elastic properties. The extracted results of elastic properties were then used to study the effects of interfacial layer properties on the elastic properties of graphene/epoxy composites. The validity of the proposed computational method based on the IGE was verified by comparing with rule of mixture (ROM), the modified Halpin-Tsai model and the experimental data. Numerical examples illustrate that the IGE has the advantages of less computation, fast convergence and high accuracy in dealing with the uneven distribution of material properties in the interfacial layer. The prediction results of Young's modulus of composites reveal that when the material properties of interfacial layer adopt the gradient model, the calculated results of Young's modulus are larger than those of uniform distribution model, ROM and the modified Halpin-Tsai model, but closer to the experimental value. The results of this research show that the property of interfacial layer is an important factor affecting the mechanical properties of composites, and provide an effective way to seek more accurate analysis of the mechanical properties of composites.
2022, 39(2): 590-600.
doi: 10.13801/j.cnki.fhclxb.20210506.002
Abstract:
Trapezoidal lattice-web reinforced foam core sandwich composites with different structural parameters were designed and manufactured by the vacuum assisted resin infusion (VARI) process. The failure modes and mechanical properties of the sandwich panels in flatwise compression loading were studied experimentally. Also, the effects of structural parameters (specimen size, lattice-web angle, lattice-web thickness) on specific compression strength, specific compression modulus and specific energy absorption were investigated. The results show that the main failure modes of the lattice-web reinforced sandwich panels are the fracture and buckling of lattice-web, and the synergistic enhancement effect between foam core and lattice-web is revealed. Compared with the control specimen, the specific compression strength, specific compression modulus and specific energy absorption of the sandwich panel with 60° lattice-web increase by 89.4%, 137.9% and 45.2%, respectively. The compression properties increase with the increase of the angle and thickness of lattice-web. The conclusions above provide reference for the design and application of lightweight sandwich composites in the ship and ocean engineering.
Trapezoidal lattice-web reinforced foam core sandwich composites with different structural parameters were designed and manufactured by the vacuum assisted resin infusion (VARI) process. The failure modes and mechanical properties of the sandwich panels in flatwise compression loading were studied experimentally. Also, the effects of structural parameters (specimen size, lattice-web angle, lattice-web thickness) on specific compression strength, specific compression modulus and specific energy absorption were investigated. The results show that the main failure modes of the lattice-web reinforced sandwich panels are the fracture and buckling of lattice-web, and the synergistic enhancement effect between foam core and lattice-web is revealed. Compared with the control specimen, the specific compression strength, specific compression modulus and specific energy absorption of the sandwich panel with 60° lattice-web increase by 89.4%, 137.9% and 45.2%, respectively. The compression properties increase with the increase of the angle and thickness of lattice-web. The conclusions above provide reference for the design and application of lightweight sandwich composites in the ship and ocean engineering.
2022, 39(2): 601-607.
doi: 10.13801/j.cnki.fhclxb.20210419.002
Abstract:
Graphene oxide (GO) was prepared by improved Hummers method with few layers of graphene as the raw material and then grafted with maleic anhydride (MAH) to obtain MAH-GO. The MAH-GO/MBMI-E51 compo-sites were prepared with in-situ polymerization using 4,4′-diaminodiphenylmethane bismaleimide resin and bisphenol A epoxy resin (MBMI-E51) as matrix, 4′4-diaminodiphenylmethane (DDM) as the curing agent and MAH-GO as the reinforcement. The microstructure of MAH-GO was characterized and the effect of the reinforcement on the mechanical properties of composite were studied. The results show that the MAH is successfully grafted on the surface of GO through chemical bonds by FTIR and XRD, with clear lamellar structure and curls on the surface. The grafting rate is about 7.26% with chemical titration method. The microstructure of the composites indicates that the fracture morphology of the composite material has changed from straight “river-like” to “dendritic” and then to dense “dimple”, with the addition of the reinforcement. The fracture mode has realized the transition from brittle fracture to ductile fracture. The impact strength, flexural strength and flexural modulus of the composites are 24.18 kJ/m2, 209 MPa and 14.15 GPa, which are 200%, 81.7% and 524% higher than those of resin matrix, when the content of MAH-GO is 1.25wt%. The mechanical properties of the composites are greatly improved.
Graphene oxide (GO) was prepared by improved Hummers method with few layers of graphene as the raw material and then grafted with maleic anhydride (MAH) to obtain MAH-GO. The MAH-GO/MBMI-E51 compo-sites were prepared with in-situ polymerization using 4,4′-diaminodiphenylmethane bismaleimide resin and bisphenol A epoxy resin (MBMI-E51) as matrix, 4′4-diaminodiphenylmethane (DDM) as the curing agent and MAH-GO as the reinforcement. The microstructure of MAH-GO was characterized and the effect of the reinforcement on the mechanical properties of composite were studied. The results show that the MAH is successfully grafted on the surface of GO through chemical bonds by FTIR and XRD, with clear lamellar structure and curls on the surface. The grafting rate is about 7.26% with chemical titration method. The microstructure of the composites indicates that the fracture morphology of the composite material has changed from straight “river-like” to “dendritic” and then to dense “dimple”, with the addition of the reinforcement. The fracture mode has realized the transition from brittle fracture to ductile fracture. The impact strength, flexural strength and flexural modulus of the composites are 24.18 kJ/m2, 209 MPa and 14.15 GPa, which are 200%, 81.7% and 524% higher than those of resin matrix, when the content of MAH-GO is 1.25wt%. The mechanical properties of the composites are greatly improved.
2022, 39(2): 608-616.
doi: 10.13801/j.cnki.fhclxb.20210526.001
Abstract:
This paper investigated the evolution of mechanical properties of flax fibre reinforced polymer compo-sites (FFRPs) conditioned in humid condition for a long term. Dry unidirectional FFRPs having fibre volume fraction of 40vol% were manufactured via vacuum assisted resin transfer moulding (VARTM). FFRPs were conditioned in 30°C, 80% relative humidity (RH) for different time (5 days, 35 days and 86 days) and their tensile properties were tested and analyzed. The results demonstrate that the moisture absorption of FFRPs fairly follows one dimensional Fickian’s second law. The equilibrated water content is around 5.3%. Tensile strength and modulus perpendicular to fibre direction decrease with moisture absorption. Fracture morphology shows that fibre-matrix bonding strength decreases after moisture absorption. Tensile strength in fibre direction is not degraded by moisture absorption, and exhibits a trend featured by a first drop followed by an increase, which has not been reported in literatures. Tensile strength in fiber direction decreases by 5.7% after being conditioned in humid for 5 days, and increases by 18.7% after 35 days. Further absorption of moisture up to 86 days (already saturated) causes a slight decrease in tensile strength but is still 13.7% higher than that at dry state. The change trend of tensile strength in fibre direction during moisture absorption can be explained as a consequence of averaging effects of several factors.
This paper investigated the evolution of mechanical properties of flax fibre reinforced polymer compo-sites (FFRPs) conditioned in humid condition for a long term. Dry unidirectional FFRPs having fibre volume fraction of 40vol% were manufactured via vacuum assisted resin transfer moulding (VARTM). FFRPs were conditioned in 30°C, 80% relative humidity (RH) for different time (5 days, 35 days and 86 days) and their tensile properties were tested and analyzed. The results demonstrate that the moisture absorption of FFRPs fairly follows one dimensional Fickian’s second law. The equilibrated water content is around 5.3%. Tensile strength and modulus perpendicular to fibre direction decrease with moisture absorption. Fracture morphology shows that fibre-matrix bonding strength decreases after moisture absorption. Tensile strength in fibre direction is not degraded by moisture absorption, and exhibits a trend featured by a first drop followed by an increase, which has not been reported in literatures. Tensile strength in fiber direction decreases by 5.7% after being conditioned in humid for 5 days, and increases by 18.7% after 35 days. Further absorption of moisture up to 86 days (already saturated) causes a slight decrease in tensile strength but is still 13.7% higher than that at dry state. The change trend of tensile strength in fibre direction during moisture absorption can be explained as a consequence of averaging effects of several factors.
2022, 39(2): 617-627.
doi: 10.13801/j.cnki.fhclxb.20210407.002
Abstract:
Three-dimensional superhydrophobic coating was sprayed on carbon steel by adjusting the content and mass ratio of Al2O3-ZrO2 fillers based on poly-benzoxazine (PBA) resin. Contact angle measuring, scanning electron microscope, friction and wear experiment and three-dimensional super depth of field microscope were used to study the structure-function relationship between the water contact angle on the surface of Al2O3-ZrO2/PBA coatings and their microscopic surface morphologies. The effects of different Al2O3-ZrO2 filler contents on the friction coefficient of coatings were compared. A mathematical model was established according to the relationship between the mass loss of 3D superhydrophobic coating and the friction distance under different loads, to predict the service life of the coating. The chemical stability of 3D superhydrophobic coating was investigated by employing different temperatures and different UV illumination time as the stimulation of external environment. The obtained results show that the contact angle of the coating reaches 154° when the mass ratio of Al2O3∶ZrO2∶PBA is 1∶1∶2. The 3D superhydrophobic coating still exhibit superhydrophobic property (150°) even after suffering 180 cm friction distance under 5.66 kPa. The surface of the coating shows super hydrophobicity even at 300℃ after 1 h, indicating that the three-dimensional superhydrophobic coating behaves good chemical stability. The coating loses its superhydrophobic property after 30 min UV irradiation, and the superhydrophobic property can be quickly recovered after friction self-repairing. Besides, the anti-corrosion performance of the 3D superhydrophobic coating was also investigated, electrochemical tests show that the superhydrophobic coating has high impedance and behaves a good protection on carbon steel substrate.
Three-dimensional superhydrophobic coating was sprayed on carbon steel by adjusting the content and mass ratio of Al2O3-ZrO2 fillers based on poly-benzoxazine (PBA) resin. Contact angle measuring, scanning electron microscope, friction and wear experiment and three-dimensional super depth of field microscope were used to study the structure-function relationship between the water contact angle on the surface of Al2O3-ZrO2/PBA coatings and their microscopic surface morphologies. The effects of different Al2O3-ZrO2 filler contents on the friction coefficient of coatings were compared. A mathematical model was established according to the relationship between the mass loss of 3D superhydrophobic coating and the friction distance under different loads, to predict the service life of the coating. The chemical stability of 3D superhydrophobic coating was investigated by employing different temperatures and different UV illumination time as the stimulation of external environment. The obtained results show that the contact angle of the coating reaches 154° when the mass ratio of Al2O3∶ZrO2∶PBA is 1∶1∶2. The 3D superhydrophobic coating still exhibit superhydrophobic property (150°) even after suffering 180 cm friction distance under 5.66 kPa. The surface of the coating shows super hydrophobicity even at 300℃ after 1 h, indicating that the three-dimensional superhydrophobic coating behaves good chemical stability. The coating loses its superhydrophobic property after 30 min UV irradiation, and the superhydrophobic property can be quickly recovered after friction self-repairing. Besides, the anti-corrosion performance of the 3D superhydrophobic coating was also investigated, electrochemical tests show that the superhydrophobic coating has high impedance and behaves a good protection on carbon steel substrate.
2022, 39(2): 628-636.
doi: 10.13801/j.cnki.fhclxb.20210426.003
Abstract:
Composite photocatalytic materials were synthesized by liquid-phase ultrasonic exfoliation-photochemical deposition method-impregnation method of monolithic Ag, thin layer of graphitic phase carbon nitride (g-C3N4) and silica-alumina colloidal spheres (SiO2). A formaldehyde degradation hermetic chamber was designed to investigate the photocatalytic properties of g-C3N4, Ag-g-C3N4 and g-C3N4-Ag/SiO2 materials and their degradation effects on formaldehyde. The results show that the efficiency of degradation of formaldehyde can reach up to 65.6% for SAG materials under visible light source conditions. 40% relative humidity can effectively enhance the degradation efficiency.The formaldehyde degradation efficiency decreases by only 9.71% when the silica-alumina spheres load with 30 mg 4%Ag/g-C3N4 are recycled for 16 times. The results of material characterization show that the visible light absorption intensity and absorption range of the material are enhanced by ultrasonic stripping and the introduction of Ag, and the separation of photogenerated electrons and holes are effectively promoted, which effectively enhance the degradation efficiency of formaldehyde molecules. The results show that the g-C3N4-Ag/SiO2 material has excellent stability and good photocatalytic performance, which provides a better scientific basis for the application of practical organic pollutant treatment.
Composite photocatalytic materials were synthesized by liquid-phase ultrasonic exfoliation-photochemical deposition method-impregnation method of monolithic Ag, thin layer of graphitic phase carbon nitride (g-C3N4) and silica-alumina colloidal spheres (SiO2). A formaldehyde degradation hermetic chamber was designed to investigate the photocatalytic properties of g-C3N4, Ag-g-C3N4 and g-C3N4-Ag/SiO2 materials and their degradation effects on formaldehyde. The results show that the efficiency of degradation of formaldehyde can reach up to 65.6% for SAG materials under visible light source conditions. 40% relative humidity can effectively enhance the degradation efficiency.The formaldehyde degradation efficiency decreases by only 9.71% when the silica-alumina spheres load with 30 mg 4%Ag/g-C3N4 are recycled for 16 times. The results of material characterization show that the visible light absorption intensity and absorption range of the material are enhanced by ultrasonic stripping and the introduction of Ag, and the separation of photogenerated electrons and holes are effectively promoted, which effectively enhance the degradation efficiency of formaldehyde molecules. The results show that the g-C3N4-Ag/SiO2 material has excellent stability and good photocatalytic performance, which provides a better scientific basis for the application of practical organic pollutant treatment.
2022, 39(2): 637-644.
doi: 10.13801/j.cnki.fhclxb.20210412.001
Abstract:
A post-filling method was proposed to prepare composite photonic crystals with both stability and good structural color effects. The patterned Poly(styrene-methacrylic acid) (P(St-MAA)) photonic crystal color structure was prepared by adopting the colloidal microsphere self-assembly method, and then the P(St-MAA) photonic crystal was filled with SiO2 sol. The filling conditions of SiO2 were optimized, and the structural color effect and stability changes of the photonic crystal color structure before and after filling were compared. The results show that: P(St-MAA) colloidal microspheres with particle diameters of 230 nm, 258 nm and 287 nm can be constructed to obtain photonic crystals with regular arrangement and bright structure, but the stability of the crystal structure is not good; when the concentration of SiO2 does not exceed 30wt% and the filling time is less than 5 min, the SiO2-P(St-MAA) composite photonic crystal with bright structure color can be prepared; under the same stability test conditions, the stability of the composite photonic crystal is significantly improved, and the structure color effect is not easy to subtract, which is mainly due to the SiO2 acting like a “bridge”, strengthening the adhesion of adjacent P(St-MAA) colloidal microspheres, and enhancing the adhesion between the photonic crystal layer and the substrate. This research will provide new ideas for the construction of high-quality photonic crystals, and is expected to promote the practical application of photonic crystal chromogenic structures.
A post-filling method was proposed to prepare composite photonic crystals with both stability and good structural color effects. The patterned Poly(styrene-methacrylic acid) (P(St-MAA)) photonic crystal color structure was prepared by adopting the colloidal microsphere self-assembly method, and then the P(St-MAA) photonic crystal was filled with SiO2 sol. The filling conditions of SiO2 were optimized, and the structural color effect and stability changes of the photonic crystal color structure before and after filling were compared. The results show that: P(St-MAA) colloidal microspheres with particle diameters of 230 nm, 258 nm and 287 nm can be constructed to obtain photonic crystals with regular arrangement and bright structure, but the stability of the crystal structure is not good; when the concentration of SiO2 does not exceed 30wt% and the filling time is less than 5 min, the SiO2-P(St-MAA) composite photonic crystal with bright structure color can be prepared; under the same stability test conditions, the stability of the composite photonic crystal is significantly improved, and the structure color effect is not easy to subtract, which is mainly due to the SiO2 acting like a “bridge”, strengthening the adhesion of adjacent P(St-MAA) colloidal microspheres, and enhancing the adhesion between the photonic crystal layer and the substrate. This research will provide new ideas for the construction of high-quality photonic crystals, and is expected to promote the practical application of photonic crystal chromogenic structures.
2022, 39(2): 645-655.
doi: 10.13801/j.cnki.fhclxb.20210513.002
Abstract:
The SiO2 particles with diameter of 1 μm, 30 nm and 100 nm were used as additive particles and low-density polyethylene (LDPE) as matrix to prepare the three kinds of SiO2/LDPE composites. The crystallization behavior and crystallinity of LDPE and three kinds of SiO2/LDPE composites were analyzed, the relative dielectric constant εr and loss factor tanδ changes of each material with frequency were measured, and the conductance current and space charge characteristics of the composites were investigated. The results show that the smaller the particle size is, the smaller the crystal size and grains spacing of the composite materials are. After adding 30 nm SiO2 particles, the crystallinity increases significantly. The microstructure formed by adding 100 nm SiO2 particles can effectively limit the chain segment movement, which makes it difficult to establish the polarization of the composites. The addition of large size particles can destroy the original crystal structure, and the new crystal structure can promote the carrier migration. Among the three SiO2 particles, the addition of SiO2 particles at 30 nm can effectively inhibit the space charge, while the addition of SiO2 particles at 100 nm can cause the heterogeneous charge accumulation near the electrode.
The SiO2 particles with diameter of 1 μm, 30 nm and 100 nm were used as additive particles and low-density polyethylene (LDPE) as matrix to prepare the three kinds of SiO2/LDPE composites. The crystallization behavior and crystallinity of LDPE and three kinds of SiO2/LDPE composites were analyzed, the relative dielectric constant εr and loss factor tanδ changes of each material with frequency were measured, and the conductance current and space charge characteristics of the composites were investigated. The results show that the smaller the particle size is, the smaller the crystal size and grains spacing of the composite materials are. After adding 30 nm SiO2 particles, the crystallinity increases significantly. The microstructure formed by adding 100 nm SiO2 particles can effectively limit the chain segment movement, which makes it difficult to establish the polarization of the composites. The addition of large size particles can destroy the original crystal structure, and the new crystal structure can promote the carrier migration. Among the three SiO2 particles, the addition of SiO2 particles at 30 nm can effectively inhibit the space charge, while the addition of SiO2 particles at 100 nm can cause the heterogeneous charge accumulation near the electrode.
2022, 39(2): 656-663.
doi: 10.13801/j.cnki.fhclxb.20210518.009
Abstract:
TiO2/graphene nanocomposites were synthesized from graphene oxide (GO), C12H28N2 and TiO2 sol by three-step method as follows: Dodecanediamine pre-intercalating, ion exchange, and interlayer in-situ formation of TiO2 by calcined. The properties and structures of TiO2/graphene nanocomposites with sandwich structure were characterized by XRD, Raman, FTIR, TEM, TG, UV-Vis and PL. The photocatalytic degradation performance of TiO2/graphene composites prepared with different amounts of TiO2 were investigated. The crystallization of TiO2 and the reduction of GO were significantly increased simultaneously during calcination. According to XRD and FTIR results, TiO2 nanoparticles have formed in situ between the interlayer of graphene and anchored on graphene with chemically-bonded. Therefore, it can be concluded that the TiO2/graphene nanocomposites with sandwich structure are prepared successfully. TiO2/graphene composites show the best photocatalytic degradation of ciprofloxacin (CIP) when the mass fraction of TiO2 is 65.5wt%, and the degradation rate reaches 90% after 150 min under visible light irradiation, which is higher than pure TiO2 nanoparticles (28%, 150 min). It can be mainly attributed to the special sandwich structure with enhanced photoinduced electron-hole separation. The photocatalyst stability test shows that TiO2/graphene nanocomposites possess high photostability and structure stability for potential practical applications in environmental purification.
TiO2/graphene nanocomposites were synthesized from graphene oxide (GO), C12H28N2 and TiO2 sol by three-step method as follows: Dodecanediamine pre-intercalating, ion exchange, and interlayer in-situ formation of TiO2 by calcined. The properties and structures of TiO2/graphene nanocomposites with sandwich structure were characterized by XRD, Raman, FTIR, TEM, TG, UV-Vis and PL. The photocatalytic degradation performance of TiO2/graphene composites prepared with different amounts of TiO2 were investigated. The crystallization of TiO2 and the reduction of GO were significantly increased simultaneously during calcination. According to XRD and FTIR results, TiO2 nanoparticles have formed in situ between the interlayer of graphene and anchored on graphene with chemically-bonded. Therefore, it can be concluded that the TiO2/graphene nanocomposites with sandwich structure are prepared successfully. TiO2/graphene composites show the best photocatalytic degradation of ciprofloxacin (CIP) when the mass fraction of TiO2 is 65.5wt%, and the degradation rate reaches 90% after 150 min under visible light irradiation, which is higher than pure TiO2 nanoparticles (28%, 150 min). It can be mainly attributed to the special sandwich structure with enhanced photoinduced electron-hole separation. The photocatalyst stability test shows that TiO2/graphene nanocomposites possess high photostability and structure stability for potential practical applications in environmental purification.
2022, 39(2): 664-676.
doi: 10.13801/j.cnki.fhclxb.20210513.007
Abstract:
Carbon nanotubes/polyaniline (CNT/PANI) buckypaper self-supporting flexible electrodes with a diameter of about 120 mm and a thickness of about 10 μm were obtained by directional pressure filtration technology. CNTs distributed uniformly and dispersed in the electrode, and PANI was uniformly embedded in the CNT network. PANI was spherical particles of nanometer to submicron size, with a maximum loading capacity of 2.7 mg·cm−2. The electrode with PANI loading of 2.2 mg·cm−2 has a porosity of 70.33%, a density of 0.4 g·cm−3 and a total pore area of 67.31 m2·g−1. The electrode can be wound several times around the glass rod with diameter of 4 mm without damage. At the current density of 4 mA·cm−2, the specific capacitance of the electrode is 1.88 F·cm−2. In the process of 1200 charging-discharging cycles, the specific capacitance decreases first and then increases, and reaches 2.41 F·cm−2 at the 900th cycle, and the capacity retention rate is 125.78% at the 1 200th cycle. After 500 times of bending at 180° angle, the retention rate of capacity is 78.43%. The symmetrical sandwich structure supercapacitor assembled by this electrode has a capacitance of 0.48 F·cm−2 at a current density of 5 mA·cm−2. Its capacity retention rate after 1000 charge-discharge cycles is 94.3%. Its energy density and power density are 213.75 mW·h·cm−3 and 2163.22 mW·cm−3, respectively.
Carbon nanotubes/polyaniline (CNT/PANI) buckypaper self-supporting flexible electrodes with a diameter of about 120 mm and a thickness of about 10 μm were obtained by directional pressure filtration technology. CNTs distributed uniformly and dispersed in the electrode, and PANI was uniformly embedded in the CNT network. PANI was spherical particles of nanometer to submicron size, with a maximum loading capacity of 2.7 mg·cm−2. The electrode with PANI loading of 2.2 mg·cm−2 has a porosity of 70.33%, a density of 0.4 g·cm−3 and a total pore area of 67.31 m2·g−1. The electrode can be wound several times around the glass rod with diameter of 4 mm without damage. At the current density of 4 mA·cm−2, the specific capacitance of the electrode is 1.88 F·cm−2. In the process of 1200 charging-discharging cycles, the specific capacitance decreases first and then increases, and reaches 2.41 F·cm−2 at the 900th cycle, and the capacity retention rate is 125.78% at the 1 200th cycle. After 500 times of bending at 180° angle, the retention rate of capacity is 78.43%. The symmetrical sandwich structure supercapacitor assembled by this electrode has a capacitance of 0.48 F·cm−2 at a current density of 5 mA·cm−2. Its capacity retention rate after 1000 charge-discharge cycles is 94.3%. Its energy density and power density are 213.75 mW·h·cm−3 and 2163.22 mW·cm−3, respectively.
2022, 39(2): 677-684.
doi: 10.13801/j.cnki.fhclxb.20210513.001
Abstract:
As a widely used antibiotic, tetracycline exists in water environment for a long time and is difficult to be degraded naturally, which does great harm to ecological environment and human health. BiOI and Bi2O3/BiOI photocatalysts were prepared by simple room temperature stirring method and solvothermal method. The morphology and structure of the materials were characterized by XRD, SEM, FTIR, UV-Vis, PL and EIS. The effects of different preparation conditions on the degradation of tetracycline by Bi2O3/BiOI composite photocatalytic material under simulated sunlight were investigated. The results show that when the molar ratio of Bi2O3 to BiOI is 0.8∶1, the reaction pH is 5, the reaction temperature is 180℃, the reaction time is 20 h, the composite photocatalytic material has the best degradation effect on tetracycline, which can reach 75% in 3 h. And the kinetic rate constants are 1.75 times and 1.56 times of that of single BiOI and Bi2O3, respectively. A catalytic mechanism of binary heterojunction photocatalyst is proposed to explain the improved photocatalytic activity.
As a widely used antibiotic, tetracycline exists in water environment for a long time and is difficult to be degraded naturally, which does great harm to ecological environment and human health. BiOI and Bi2O3/BiOI photocatalysts were prepared by simple room temperature stirring method and solvothermal method. The morphology and structure of the materials were characterized by XRD, SEM, FTIR, UV-Vis, PL and EIS. The effects of different preparation conditions on the degradation of tetracycline by Bi2O3/BiOI composite photocatalytic material under simulated sunlight were investigated. The results show that when the molar ratio of Bi2O3 to BiOI is 0.8∶1, the reaction pH is 5, the reaction temperature is 180℃, the reaction time is 20 h, the composite photocatalytic material has the best degradation effect on tetracycline, which can reach 75% in 3 h. And the kinetic rate constants are 1.75 times and 1.56 times of that of single BiOI and Bi2O3, respectively. A catalytic mechanism of binary heterojunction photocatalyst is proposed to explain the improved photocatalytic activity.
2022, 39(2): 685-694.
doi: 10.13801/j.cnki.fhclxb.20210517.002
Abstract:
To improve the mechanical connection performance of fabricated structural joint, the material properties of polypropylene (PP) fiber grouting material and the mechanical properties of its rebar sleeve joint were studied. The mechanical properties of grouting material with different PP fiber contents and length were tested. The optimum content (Volume ratio to ordinary (JZ) grouting material) and length of PP fiber is 0.5% and 9 mm, respectively. Taking JZ grouting material as control group, the anchorage length of 4d, 6d and 8d (d is the diameter of bar) was set and the uniaxial tensile test was carried out. The bond stress distribution of PP fiber grouting material was also studied by using Bragg Grating sensors (FBG) and strain gauge. The results show that: The minimum anchorage length of rebar sleeve of PP fiber reinforced grouting material is more than 6d; PP fiber can effectively improve the joint toughness, enhance the bond anchorage effect of the sleeve, and improve the uniform distribution of the bond stress of the reinforcement, which shows “saddle” or “inclined ladder” distribution; the results of FBG sensor and strain gauge are basically consistent, and the accuracy of strain data collected by FBG sensor is higher than that of strain gauge.
To improve the mechanical connection performance of fabricated structural joint, the material properties of polypropylene (PP) fiber grouting material and the mechanical properties of its rebar sleeve joint were studied. The mechanical properties of grouting material with different PP fiber contents and length were tested. The optimum content (Volume ratio to ordinary (JZ) grouting material) and length of PP fiber is 0.5% and 9 mm, respectively. Taking JZ grouting material as control group, the anchorage length of 4d, 6d and 8d (d is the diameter of bar) was set and the uniaxial tensile test was carried out. The bond stress distribution of PP fiber grouting material was also studied by using Bragg Grating sensors (FBG) and strain gauge. The results show that: The minimum anchorage length of rebar sleeve of PP fiber reinforced grouting material is more than 6d; PP fiber can effectively improve the joint toughness, enhance the bond anchorage effect of the sleeve, and improve the uniform distribution of the bond stress of the reinforcement, which shows “saddle” or “inclined ladder” distribution; the results of FBG sensor and strain gauge are basically consistent, and the accuracy of strain data collected by FBG sensor is higher than that of strain gauge.
2022, 39(2): 695-706.
doi: 10.13801/j.cnki.fhclxb.20210420.003
Abstract:
In order to explore a new way of recycle use of building solid waste, a composite structure with building waste particles constrained by basalt fiber plain woven fabric was proposed. Its mechanical properties and energy absorption characteristics were investigated through quasi-static uniaxial compression test. The impacts of the type of building solid waste particles, the size grade of the building solid waste particles, and the number of constrained layers of basalt plain woven fabric on the response process, failure mode, load transfer, and energy absorption were discussed, respectively. The results show that the peak load of waste brick particles (16.54-27.89 kN) and waste concrete particles (17.99-32.33 kN) under the constraint of single-layer basalt fiber plain woven fabric decrease with increasing particle size. Compared with waste concrete particles, although the waste brick particles provide lower peak load at each particle size grade, the latter exhibits a stable plateau stage (the plateau stress range is 0.87-1.26 MPa) and obvious densification strain (about 0.3), which is an ideal energy-absorbing structure. Increasing the number of constrained layers of basalt plain woven fabric for waste brick particles is able to significantly increase the peak load and specific energy absorption, however, it is not an ideal energy absorption structure due to the lack of plateau stage and obvious densification strain.
In order to explore a new way of recycle use of building solid waste, a composite structure with building waste particles constrained by basalt fiber plain woven fabric was proposed. Its mechanical properties and energy absorption characteristics were investigated through quasi-static uniaxial compression test. The impacts of the type of building solid waste particles, the size grade of the building solid waste particles, and the number of constrained layers of basalt plain woven fabric on the response process, failure mode, load transfer, and energy absorption were discussed, respectively. The results show that the peak load of waste brick particles (16.54-27.89 kN) and waste concrete particles (17.99-32.33 kN) under the constraint of single-layer basalt fiber plain woven fabric decrease with increasing particle size. Compared with waste concrete particles, although the waste brick particles provide lower peak load at each particle size grade, the latter exhibits a stable plateau stage (the plateau stress range is 0.87-1.26 MPa) and obvious densification strain (about 0.3), which is an ideal energy-absorbing structure. Increasing the number of constrained layers of basalt plain woven fabric for waste brick particles is able to significantly increase the peak load and specific energy absorption, however, it is not an ideal energy absorption structure due to the lack of plateau stage and obvious densification strain.
2022, 39(2): 707-717.
doi: 10.13801/j.cnki.fhclxb.20210316.001
Abstract:
In order to study the shear behavior of ultra-high performance concrete (UHPC) beams without stirrups, 9 externally prestressed UHPC beams without stirrups were fabricated. The experimental parameters included the level of prestress, shear span-to-depth ratio, longitudinal reinforcement ratio and volume fraction of steel fibers. Four-point loading method was used to obtain the failure patterns, cracking strength and ultimate strength. The results show that the non-prestressed UHPC beam under the shear span-to-depth ratio of 1.0 suffers from flexural failure. However, the flexural resistance of the normal section of UHPC beam is strengthened by a prestressing tension of 25% ultimate strength of the strands, resulting in an increase of the flexural moment by 157% and turning into a shear failure. Compared with non-prestressed UHPC beam, the cracking loads of UHPC beams tensioned by 25% prestress and 40% prestress increase by 1.2 times and 2.6 times, respectively, which effectively inhibit the formation of cracks. The UHPC beams with 40% prestress under shear span-to-depth ratio of 1.0 and 1.5 fail in shear. However, when the shear span-to-depth ratio increases to 2.0, the UHPC beam suffers from a flexural failure, which leads to concrete crushing in the compression zone. The formulae of the codes underestimate the shear capacity of the externally prestressed UHPC beams, since the average ratios of the experimental shear capacity to the calculated one of the inclined section are 2.28 and 3.21, respectively.
In order to study the shear behavior of ultra-high performance concrete (UHPC) beams without stirrups, 9 externally prestressed UHPC beams without stirrups were fabricated. The experimental parameters included the level of prestress, shear span-to-depth ratio, longitudinal reinforcement ratio and volume fraction of steel fibers. Four-point loading method was used to obtain the failure patterns, cracking strength and ultimate strength. The results show that the non-prestressed UHPC beam under the shear span-to-depth ratio of 1.0 suffers from flexural failure. However, the flexural resistance of the normal section of UHPC beam is strengthened by a prestressing tension of 25% ultimate strength of the strands, resulting in an increase of the flexural moment by 157% and turning into a shear failure. Compared with non-prestressed UHPC beam, the cracking loads of UHPC beams tensioned by 25% prestress and 40% prestress increase by 1.2 times and 2.6 times, respectively, which effectively inhibit the formation of cracks. The UHPC beams with 40% prestress under shear span-to-depth ratio of 1.0 and 1.5 fail in shear. However, when the shear span-to-depth ratio increases to 2.0, the UHPC beam suffers from a flexural failure, which leads to concrete crushing in the compression zone. The formulae of the codes underestimate the shear capacity of the externally prestressed UHPC beams, since the average ratios of the experimental shear capacity to the calculated one of the inclined section are 2.28 and 3.21, respectively.
Preparation and properties of mechanically induced double crosslinked anisotropic cellulose hydrogel
2022, 39(2): 718-725.
doi: 10.13801/j.cnki.fhclxb.20210414.001
Abstract:
In order to improve the softness and fragility of traditional cellulose hydrogel materials, broaden its application area and develop cellulose hydrogels with excellent mechanical properties, the cellulose hydrogel with loose chemical crosslinking network was prepared by adding epichlorohydrin into cellulose dissolved in LiOH-urea aqueous solution. Then the alkali-urea inclusion complex in the acid solution was removed to introduce physical crosslinking. The dual-crosslinking cellulose hydrogel with temporary orientation was obtained. On this basis, the researcher regulated mechanical force to stretch and fix the hydrogel with double network structure along the length direction to obtain anisotropic cellulose hydrogels with different mechanical properties. Research shows, the maximum tensile strength of cellulose hydrogels can reach 2.96 MPa after stretching, and the cellulose hydrogel exhibits color polarization phenomenon under polarized light, showing typical optical anisotropy. This method can construct cellulose hydrogels with high strength and optical anisotropy. This type of hydrogels has good application prospects in the fields of intelligent soft matter and others.
In order to improve the softness and fragility of traditional cellulose hydrogel materials, broaden its application area and develop cellulose hydrogels with excellent mechanical properties, the cellulose hydrogel with loose chemical crosslinking network was prepared by adding epichlorohydrin into cellulose dissolved in LiOH-urea aqueous solution. Then the alkali-urea inclusion complex in the acid solution was removed to introduce physical crosslinking. The dual-crosslinking cellulose hydrogel with temporary orientation was obtained. On this basis, the researcher regulated mechanical force to stretch and fix the hydrogel with double network structure along the length direction to obtain anisotropic cellulose hydrogels with different mechanical properties. Research shows, the maximum tensile strength of cellulose hydrogels can reach 2.96 MPa after stretching, and the cellulose hydrogel exhibits color polarization phenomenon under polarized light, showing typical optical anisotropy. This method can construct cellulose hydrogels with high strength and optical anisotropy. This type of hydrogels has good application prospects in the fields of intelligent soft matter and others.
2022, 39(2): 726-735.
doi: 10.13801/j.cnki.fhclxb.20210514.002
Abstract:
Amidoxime polyacrylonitrile (AOPAN)-β-cyclodextrin (β-CD) nanofiber membranes were synthesized in one step using polyacrylonitrile (PAN) and β-CD as raw materials by in-situ amidoxime modification with hydroxylamine hydrochloride and then electrospinning technology. Evaluating by morphology and adsorption capacity, the preparation condition of modification was optimized. The morphology, composition and properties of the membranes were characterized by SEM, FTIR and surface tension meter. The results show that under the optimized modification process conditions, which the molar ratio of cyanogroup to hydroxylamine is 1∶1 and the modification time is 2 h, the morphology distribution of AOPAN-β-CD nanofiber membrane is more uniform and the fiber diameter is about 230 nm, and the adsorption capacity of the fiber membrane reaches 78.62 mg/g.
Amidoxime polyacrylonitrile (AOPAN)-β-cyclodextrin (β-CD) nanofiber membranes were synthesized in one step using polyacrylonitrile (PAN) and β-CD as raw materials by in-situ amidoxime modification with hydroxylamine hydrochloride and then electrospinning technology. Evaluating by morphology and adsorption capacity, the preparation condition of modification was optimized. The morphology, composition and properties of the membranes were characterized by SEM, FTIR and surface tension meter. The results show that under the optimized modification process conditions, which the molar ratio of cyanogroup to hydroxylamine is 1∶1 and the modification time is 2 h, the morphology distribution of AOPAN-β-CD nanofiber membrane is more uniform and the fiber diameter is about 230 nm, and the adsorption capacity of the fiber membrane reaches 78.62 mg/g.
2022, 39(2): 736-745.
doi: 10.13801/j.cnki.fhclxb.20210506.003
Abstract:
A composite adsorbent of CaC2O4-DB/CTS was prepared using chitosan (CTS) and the hybrid materials of CaC2O4 and direct claret B (CaC2O4-DB/CTS) by the method of blending in-situ immobilization. CTS and CaC2O4-DB/CTS were characterized by SEM, BET and FTIR. The immobilization of CaC2O4-DB only increases the specific surface area and binding sites without changing the morphology and structure of CTS. The effects of adsorption time, the initial concentration of ethyl violet (EV), pH and temperature of the solution on the adsorption properties of CaC2O4-DB/CTS composite material were investigated in detail, and the adsorption kinetics and thermodynamic behavior of EV on CaC2O4-DB/CTS were preliminarily discussed. The results show that the removal rate of dye and chemical oxygen demand (COD) reach 95% and 90% for 100 mg/L EV solution (COD is 187 mg/L), respectively, under conditions of room temperature, CaC2O4-DB/CTS dosage of 6 g/L, adsorption time of 3 h and pH=8. The adsorption behavior of EV by the adsorbent is spontaneous and in accordance with Langmuir model and the quasi-second-order kinetic model. The adsorption process is controlled by intra-particle diffusion and the chemical adsorption.
A composite adsorbent of CaC2O4-DB/CTS was prepared using chitosan (CTS) and the hybrid materials of CaC2O4 and direct claret B (CaC2O4-DB/CTS) by the method of blending in-situ immobilization. CTS and CaC2O4-DB/CTS were characterized by SEM, BET and FTIR. The immobilization of CaC2O4-DB only increases the specific surface area and binding sites without changing the morphology and structure of CTS. The effects of adsorption time, the initial concentration of ethyl violet (EV), pH and temperature of the solution on the adsorption properties of CaC2O4-DB/CTS composite material were investigated in detail, and the adsorption kinetics and thermodynamic behavior of EV on CaC2O4-DB/CTS were preliminarily discussed. The results show that the removal rate of dye and chemical oxygen demand (COD) reach 95% and 90% for 100 mg/L EV solution (COD is 187 mg/L), respectively, under conditions of room temperature, CaC2O4-DB/CTS dosage of 6 g/L, adsorption time of 3 h and pH=8. The adsorption behavior of EV by the adsorbent is spontaneous and in accordance with Langmuir model and the quasi-second-order kinetic model. The adsorption process is controlled by intra-particle diffusion and the chemical adsorption.
2022, 39(2): 746-758.
doi: 10.13801/j.cnki.fhclxb.20210422.001
Abstract:
In order to investigate the effect of corrosion on the surface properties of steel plate and interfacial bonding properties between CFRP plate and corroded steel plate, surface characteristic test of corroded steel plates with six kinds of corrosion duration and tensile test of thirty-four double-lap specimens with CFRP plates and corroded steel plates were carried out. The effects of corrosion duration on the morphology and surface roughness, apparent contact angle and surface free energy of steel plate, and the failure mode, effective bond length and ultimate load of bonding interface between CFRP plate and corroded steel plate were revealed. Test results show that with the increase of corrosion duration, pitting corrosion and uniform corrosion alternately play the dominant role on the surface topography, the surface roughness and surface free energy of the corroded steel plates fluctuate up and down continuously. The failure mode of bonding interface between CFRP plate and corroded steel plate is mainly the mixed of steel/adhesive interfacial debonding and CFRP/adhesive interfacial debonding, and the corrosion duration only has a certain influence on the area proportion of the mixed failure type. As for the specimens with the si-milar adhesive thickness, the effective bond length of the corroded specimens is significantly larger than that of the un-corroded ones, the effective bond length for the specimens with the corrosion duration of 0-12 months and the adhesive thickness of 0.21-0.7 mm are approximately 63.75-91.5 mm. With the increase of corrosion duration, the ultimate bearing capacity of the bonding interface increases at first and tends to be stable afterwards, the increase of surface area, surface free energy and surface roughness caused by corrosion plays the favorable factor on the ultimate bearing capacity.
In order to investigate the effect of corrosion on the surface properties of steel plate and interfacial bonding properties between CFRP plate and corroded steel plate, surface characteristic test of corroded steel plates with six kinds of corrosion duration and tensile test of thirty-four double-lap specimens with CFRP plates and corroded steel plates were carried out. The effects of corrosion duration on the morphology and surface roughness, apparent contact angle and surface free energy of steel plate, and the failure mode, effective bond length and ultimate load of bonding interface between CFRP plate and corroded steel plate were revealed. Test results show that with the increase of corrosion duration, pitting corrosion and uniform corrosion alternately play the dominant role on the surface topography, the surface roughness and surface free energy of the corroded steel plates fluctuate up and down continuously. The failure mode of bonding interface between CFRP plate and corroded steel plate is mainly the mixed of steel/adhesive interfacial debonding and CFRP/adhesive interfacial debonding, and the corrosion duration only has a certain influence on the area proportion of the mixed failure type. As for the specimens with the si-milar adhesive thickness, the effective bond length of the corroded specimens is significantly larger than that of the un-corroded ones, the effective bond length for the specimens with the corrosion duration of 0-12 months and the adhesive thickness of 0.21-0.7 mm are approximately 63.75-91.5 mm. With the increase of corrosion duration, the ultimate bearing capacity of the bonding interface increases at first and tends to be stable afterwards, the increase of surface area, surface free energy and surface roughness caused by corrosion plays the favorable factor on the ultimate bearing capacity.
2022, 39(2): 759-768.
doi: 10.13801/j.cnki.fhclxb.20210513.006
Abstract:
The copper-matrix composites reinforced by graphite flake and carbon fiber were prepared by vacuum hot pressing technique. The effects of carbon fiber content on the microstructure, mechanical properties and thermal properties of the composites were discussed. The results show that the prepared graphite flake-carbon fiber/copper matrix composites have good interface bonding. The carbon fibers can be uniformly dispersed in the matrix and the bending strength of the composites can be improved when the volume fraction of 0.5vol%-1.5vol% carbon fibers is added. When the content of carbon fiber is 1.5vol%, the bending strength reaches the maximum of 126 MPa, which is increased by 46% compared with that without carbon fiber. However, the excessive addition of carbon fiber (2vol% or more) leads to an uneven distribution of carbon fiber, and the bending strength of composites decreases. The thermal conductivity of the composite decreases slightly with the addition of carbon fiber, from 549 W/(m·K) to 527 W/(m·K). The acoustic mismatch model (AMM) was used in conjunction with Digimat’s MF module to effectively predict the thermal conductivity of multiphase composites.
The copper-matrix composites reinforced by graphite flake and carbon fiber were prepared by vacuum hot pressing technique. The effects of carbon fiber content on the microstructure, mechanical properties and thermal properties of the composites were discussed. The results show that the prepared graphite flake-carbon fiber/copper matrix composites have good interface bonding. The carbon fibers can be uniformly dispersed in the matrix and the bending strength of the composites can be improved when the volume fraction of 0.5vol%-1.5vol% carbon fibers is added. When the content of carbon fiber is 1.5vol%, the bending strength reaches the maximum of 126 MPa, which is increased by 46% compared with that without carbon fiber. However, the excessive addition of carbon fiber (2vol% or more) leads to an uneven distribution of carbon fiber, and the bending strength of composites decreases. The thermal conductivity of the composite decreases slightly with the addition of carbon fiber, from 549 W/(m·K) to 527 W/(m·K). The acoustic mismatch model (AMM) was used in conjunction with Digimat’s MF module to effectively predict the thermal conductivity of multiphase composites.
2022, 39(2): 769-776.
doi: 10.13801/j.cnki.fhclxb.20210529.001
Abstract:
Based on the good neutron absorption property of B4C and the moderated neutron property of carbon fiber (CF), CF-B4C mixed-reinforced 6061Al matrix composites with different CF contents were prepared by vacuum hot pressing sintering method. The microstructure and mechanical properties of the composites were analyzed. After hot rolling with large deformation, the B4C particles are distributed evenly without large area of particle aggregation, but a small amount of B4C particles and CF are brittle. When the deformation reaches 60%, the tensile strength of the material can reach (265±3) MPa. Compared with the tensile strength of 6061Al alloy, the tensile strength values of CF-B4C/Al composites with different thicknesses increase by 80% and 112% respectively. With the increase of CF content, the strength and elongation of CF-B4C/Al composites decrease. When the content of CF reaches 5wt%, the main reason of fracture is the aggregation of fibers and the arrangement of fibers along the fracture direction.
Based on the good neutron absorption property of B4C and the moderated neutron property of carbon fiber (CF), CF-B4C mixed-reinforced 6061Al matrix composites with different CF contents were prepared by vacuum hot pressing sintering method. The microstructure and mechanical properties of the composites were analyzed. After hot rolling with large deformation, the B4C particles are distributed evenly without large area of particle aggregation, but a small amount of B4C particles and CF are brittle. When the deformation reaches 60%, the tensile strength of the material can reach (265±3) MPa. Compared with the tensile strength of 6061Al alloy, the tensile strength values of CF-B4C/Al composites with different thicknesses increase by 80% and 112% respectively. With the increase of CF content, the strength and elongation of CF-B4C/Al composites decrease. When the content of CF reaches 5wt%, the main reason of fracture is the aggregation of fibers and the arrangement of fibers along the fracture direction.
2022, 39(2): 777-787.
doi: 10.13801/j.cnki.fhclxb.20210323.001
Abstract:
Based on the transient dynamics theory and genetic optimization algorithm, the layup sequence of composite gas cylinder was optimized with the optimization goal of improving the resistance to impact damage. The genetic algorithm was realized by MATLAB software, and the impact damage analysis of composite gas cylinders was carried out by ANSYS. Through the information transmission between the two software, the optimized process was realized. Taking an aluminum-lined composite gas cylinder as an example for optimization, the results show that under the same impact energy, the matrix rupture area and the number of matrix rupture layers of optimized gas cylinder are greatly reduced, and the remaining burst pressure is significantly increased. When the impact energy is 60 J, the rupture matrix area on the surface reduces 8.8%, the number of rupture layers in the matrix reduces 14.3%, and the remaining burst pressure value increases 9.6%. The optimization algorithm established in this paper can be used to optimize the design of composite gas cylinders.
Based on the transient dynamics theory and genetic optimization algorithm, the layup sequence of composite gas cylinder was optimized with the optimization goal of improving the resistance to impact damage. The genetic algorithm was realized by MATLAB software, and the impact damage analysis of composite gas cylinders was carried out by ANSYS. Through the information transmission between the two software, the optimized process was realized. Taking an aluminum-lined composite gas cylinder as an example for optimization, the results show that under the same impact energy, the matrix rupture area and the number of matrix rupture layers of optimized gas cylinder are greatly reduced, and the remaining burst pressure is significantly increased. When the impact energy is 60 J, the rupture matrix area on the surface reduces 8.8%, the number of rupture layers in the matrix reduces 14.3%, and the remaining burst pressure value increases 9.6%. The optimization algorithm established in this paper can be used to optimize the design of composite gas cylinders.
2022, 39(2): 788-801.
doi: 10.13801/j.cnki.fhclxb.20210328.001
Abstract:
The effect of impact positions on the damage tolerance of T-stiffened composite panels was investigated by experimental methods. Low velocity impact (LVI) was carried out at two typical locations, namely the center of skin between two stiffeners and the stiffener flange tip of the panels, to introduce visible impact damage (VID). With the help of visual inspection and nondestructive detection, obvious differences in damage morphology from different impact positions were observed. Compared with the skin impact, the damage types induced by the flange tip impact were more complicated, including fiber fracture, matrix cracks, delamination, ply splitting and interface debonding. Compression-after-impact (CAI) tests were performed on the intact, skin-impacted and flange-impacted stiffened panels respectively. The experimental results show that the deformation of skin-impacted panels is restricted due to blade supports, inducing the damage initiation and causing ultimate destruction, which is extremely similar to intact panels. For the flange tip impact, whilst, damage propagation is along the transverse direction from the impact location, which is entirely different from skin impact in the damage scenario, promoting the structural failure and reducing significantly the residual compressive strength. Additionally, the digital image correlation (DIC) was used to monitor the deformation of the specimens during compression and compared with the results of contact measurement, which verified the feasibility and superiority of the test method applied to the mechanical properties of materials.
The effect of impact positions on the damage tolerance of T-stiffened composite panels was investigated by experimental methods. Low velocity impact (LVI) was carried out at two typical locations, namely the center of skin between two stiffeners and the stiffener flange tip of the panels, to introduce visible impact damage (VID). With the help of visual inspection and nondestructive detection, obvious differences in damage morphology from different impact positions were observed. Compared with the skin impact, the damage types induced by the flange tip impact were more complicated, including fiber fracture, matrix cracks, delamination, ply splitting and interface debonding. Compression-after-impact (CAI) tests were performed on the intact, skin-impacted and flange-impacted stiffened panels respectively. The experimental results show that the deformation of skin-impacted panels is restricted due to blade supports, inducing the damage initiation and causing ultimate destruction, which is extremely similar to intact panels. For the flange tip impact, whilst, damage propagation is along the transverse direction from the impact location, which is entirely different from skin impact in the damage scenario, promoting the structural failure and reducing significantly the residual compressive strength. Additionally, the digital image correlation (DIC) was used to monitor the deformation of the specimens during compression and compared with the results of contact measurement, which verified the feasibility and superiority of the test method applied to the mechanical properties of materials.
2022, 39(2): 802-811.
doi: 10.13801/j.cnki.fhclxb.20210401.001
Abstract:
A method was proposed to analysis the axisymmetric problem of composite tubes made up of winding layers with arbitrary angles. The traditional Lekhnitskii theory can obtain the exact elastic solution of the thick composite tubes with common winding layers. However, when there are 0° winding layers or isotropic layers in the thick walled tubes, singular parameters will appear in the both special layers. And the discontinuity condition between the special layer and the common layer could not be satisfied. Therefore, the reasons for the existence of singular parameters in special layers were discussed. Then, the continuity analysis and limit calculation of these parameters were carried out, so that the problem of parameter singularity was solved and the application of Lekhnitskii theory was extended to composite thick tubes with arbitrary angles. Finally, the mechanical responses of different compo-site tubes were analyzed by ABAQUS, and the results of finite element calculation were basically consistent with the developed theoretical results.
A method was proposed to analysis the axisymmetric problem of composite tubes made up of winding layers with arbitrary angles. The traditional Lekhnitskii theory can obtain the exact elastic solution of the thick composite tubes with common winding layers. However, when there are 0° winding layers or isotropic layers in the thick walled tubes, singular parameters will appear in the both special layers. And the discontinuity condition between the special layer and the common layer could not be satisfied. Therefore, the reasons for the existence of singular parameters in special layers were discussed. Then, the continuity analysis and limit calculation of these parameters were carried out, so that the problem of parameter singularity was solved and the application of Lekhnitskii theory was extended to composite thick tubes with arbitrary angles. Finally, the mechanical responses of different compo-site tubes were analyzed by ABAQUS, and the results of finite element calculation were basically consistent with the developed theoretical results.
2022, 39(2): 812-822.
doi: 10.13801/j.cnki.fhclxb.20210425.002
Abstract:
For composite material structure bolt connection, different operating conditions will change the friction coefficient between the bearing surface and the thread, thus affecting the torque coefficient, which makes the changing trend of the clamping force with tightening torque very complicated. Firstly, the theoretical analysis of the bolt tightening process was made and the express formulas of the clamping force and the bolt yield clamping force under the state of combined stress were obtained. Then, taking a certain type of bolt as the object for experimental research, under the specified target clamping force, the tightening curves under different operating conditions of lubrication, washer, and tightening speed were tested respectively. The test results show that, different lubrication conditions, washer conditions and tightening speeds have certain influences on the dispersion of clamping force and tightening torque curves, the tightening torque required when the clamping force reaches the same size, and the changing trend of clamping force with tightening torque. By studying the clamping force during bolt tightening process under the above operating conditions, it can provide some reference and basis for the precision of bolt connection structure and process design in composite material components.
For composite material structure bolt connection, different operating conditions will change the friction coefficient between the bearing surface and the thread, thus affecting the torque coefficient, which makes the changing trend of the clamping force with tightening torque very complicated. Firstly, the theoretical analysis of the bolt tightening process was made and the express formulas of the clamping force and the bolt yield clamping force under the state of combined stress were obtained. Then, taking a certain type of bolt as the object for experimental research, under the specified target clamping force, the tightening curves under different operating conditions of lubrication, washer, and tightening speed were tested respectively. The test results show that, different lubrication conditions, washer conditions and tightening speeds have certain influences on the dispersion of clamping force and tightening torque curves, the tightening torque required when the clamping force reaches the same size, and the changing trend of clamping force with tightening torque. By studying the clamping force during bolt tightening process under the above operating conditions, it can provide some reference and basis for the precision of bolt connection structure and process design in composite material components.
2022, 39(2): 823-833.
doi: 10.13801/j.cnki.fhclxb.20210420.002
Abstract:
To investigate the hyperelasticity of silicone gel, its mechanical properties were characterized by uniaxial tensile (UT) test in the temperature from −30℃ to 30℃. The stress-strain curves of silicone gel at different temperatures were obtained and found that the initial elastic modulus of silicone gel is positively correlated with temperature from −30℃ to 0℃ and negatively correlated with temperature from 0℃ to 30℃. According to UT experimental data, the selection strategies and parameter determination methods of in-built hyperelastic constitutive equations (Neo Hookean, Mooney-Rivlin, Yeoh, Arruda-Boyce, etc.) were discussed in the finite element simulation. Then based on the selected Neo Hookean model, a temperature-dependent hyperelastic constitutive model was established to describe the stress-strain response of silicone gel over a wide temperature range. The temperature-dependent model was written using UHYPER subroutine of ABAQUS. In combination with fiber Bragg grating (FBG) monitoring technology, numerical simulation and experimental monitoring of silicone gel for typical encapsulation structures were carried out during high-low temperature cycles between −30℃ and 30℃. The strain results at the observation points show that the final error between experimental measurement and numerical prediction is 7%, revealing the validity of the hyperelastic constitutive equation derived in this paper and its value in practical application.
To investigate the hyperelasticity of silicone gel, its mechanical properties were characterized by uniaxial tensile (UT) test in the temperature from −30℃ to 30℃. The stress-strain curves of silicone gel at different temperatures were obtained and found that the initial elastic modulus of silicone gel is positively correlated with temperature from −30℃ to 0℃ and negatively correlated with temperature from 0℃ to 30℃. According to UT experimental data, the selection strategies and parameter determination methods of in-built hyperelastic constitutive equations (Neo Hookean, Mooney-Rivlin, Yeoh, Arruda-Boyce, etc.) were discussed in the finite element simulation. Then based on the selected Neo Hookean model, a temperature-dependent hyperelastic constitutive model was established to describe the stress-strain response of silicone gel over a wide temperature range. The temperature-dependent model was written using UHYPER subroutine of ABAQUS. In combination with fiber Bragg grating (FBG) monitoring technology, numerical simulation and experimental monitoring of silicone gel for typical encapsulation structures were carried out during high-low temperature cycles between −30℃ and 30℃. The strain results at the observation points show that the final error between experimental measurement and numerical prediction is 7%, revealing the validity of the hyperelastic constitutive equation derived in this paper and its value in practical application.
2022, 39(2): 834-844.
doi: 10.13801/j.cnki.fhclxb.20210420.004
Abstract:
This subject mainly studies the damage evolution process and failure mode of the resin-mineral composite material used for the machine bed under typical working conditions. In this study, a four media discrete element model was established based on particle flow numerical simulation technology (Three-dimensional particle flow code, PFC3D), as well as grading and random aggregate shape. The model includes aggregate, interfacial transition zone, resin matrix and porous resin mineral composites. The failure evolution and crack distribution of resin mineral composites were studied under the typical working conditions of machine tool and the formation mechanism of crack initiation, propagation and penetration was studied from a meso-level perspective. The results show that: (1) Damage evolution of resin mineral composites can be divided into four stages. (2) Cracks appeared earlier in the interface between aggregate and resin matrix. In addition, the crushing phenomenon occurs at the weak position with parallel loading and no large aggregate support. This study provides an important reference for the study of damage properties of resin mineral composites as basic parts of machine tools.
This subject mainly studies the damage evolution process and failure mode of the resin-mineral composite material used for the machine bed under typical working conditions. In this study, a four media discrete element model was established based on particle flow numerical simulation technology (Three-dimensional particle flow code, PFC3D), as well as grading and random aggregate shape. The model includes aggregate, interfacial transition zone, resin matrix and porous resin mineral composites. The failure evolution and crack distribution of resin mineral composites were studied under the typical working conditions of machine tool and the formation mechanism of crack initiation, propagation and penetration was studied from a meso-level perspective. The results show that: (1) Damage evolution of resin mineral composites can be divided into four stages. (2) Cracks appeared earlier in the interface between aggregate and resin matrix. In addition, the crushing phenomenon occurs at the weak position with parallel loading and no large aggregate support. This study provides an important reference for the study of damage properties of resin mineral composites as basic parts of machine tools.
2022, 39(2): 845-853.
doi: 10.13801/j.cnki.fhclxb.20210331.002
Abstract:
In engineering practice, strains are used for stress analysis of composite aircraft structures, instead of stresses due to their stacking sequence dependence. Besides, for composite airplane, damage tolerant design is necessary, the compliance of airworthiness for composite structures with damages, especially barely visible impact damages (BVID) should be assessed. Thus for civil aircraft structural design, a credible strain based failure criterion for composites that containing damage is in demand for stress prediction. In this paper, a combined strain failure criterion for laminates was introduced. In order to verify the conservation of this failure criterion, biaxial loading tests were designed. Quasi-isotropic T800 carbon fiber reinforced epoxy resin matrix composite laminates with BVID were used for in-plane failure tests under various load conditions. Various load conditions with different combination of tension, compression and shearing loads were obtained through diversified design of load ratios. It is shown from the comparison of theoretical results and test results that all the theoretical failure loads are lower than experimental ones with a ratio of about 80%. The criterion is conserved to assure the safety of structures, but not too conserved to bring unnecessary weight to structures, thus it is suitable for engineering exercise.
In engineering practice, strains are used for stress analysis of composite aircraft structures, instead of stresses due to their stacking sequence dependence. Besides, for composite airplane, damage tolerant design is necessary, the compliance of airworthiness for composite structures with damages, especially barely visible impact damages (BVID) should be assessed. Thus for civil aircraft structural design, a credible strain based failure criterion for composites that containing damage is in demand for stress prediction. In this paper, a combined strain failure criterion for laminates was introduced. In order to verify the conservation of this failure criterion, biaxial loading tests were designed. Quasi-isotropic T800 carbon fiber reinforced epoxy resin matrix composite laminates with BVID were used for in-plane failure tests under various load conditions. Various load conditions with different combination of tension, compression and shearing loads were obtained through diversified design of load ratios. It is shown from the comparison of theoretical results and test results that all the theoretical failure loads are lower than experimental ones with a ratio of about 80%. The criterion is conserved to assure the safety of structures, but not too conserved to bring unnecessary weight to structures, thus it is suitable for engineering exercise.
2022, 39(2): 854-862.
doi: 10.13801/j.cnki.fhclxb.20210420.001
Abstract:
Composites are termed as important lightweight materials because of their high specific stiffness and strength. The application of composites in automotive industry can be one effective way to reduce environmental pollution and energy shortages. A composites bumper, which is 27% lighter than the aluminum counterpart, was designed and fabricated using wet compression molding with carbon fiber. Then, 40% frontal collision following RCAR standard were performed on these bumpers. Meanwhile, the finite element models were built up in LS-DYNA and used for parameter discussion after validation. The thickness of energy absorption box can increase the crashworthiness of the bumper, while the energy absorption capability can be enhanced after introducing a bioinspired helicoidal fiber arrangement. Also, the composites bumper is demonstrated to outperform the metal one under the same weight.
Composites are termed as important lightweight materials because of their high specific stiffness and strength. The application of composites in automotive industry can be one effective way to reduce environmental pollution and energy shortages. A composites bumper, which is 27% lighter than the aluminum counterpart, was designed and fabricated using wet compression molding with carbon fiber. Then, 40% frontal collision following RCAR standard were performed on these bumpers. Meanwhile, the finite element models were built up in LS-DYNA and used for parameter discussion after validation. The thickness of energy absorption box can increase the crashworthiness of the bumper, while the energy absorption capability can be enhanced after introducing a bioinspired helicoidal fiber arrangement. Also, the composites bumper is demonstrated to outperform the metal one under the same weight.
