2020 Vol. 37, No. 1
2020, 37(1): 1-15.
doi: 10.13801/j.cnki.fhclxb.20190917.004
Abstract:
Based on the demand of the third generation of advanced composites characterized by high strength, high toughness, high modulus and the balance of compressive and tensile strength, the development history of prediction model of continuous fiber reinforced polymer composite compressive strength was reviewed. The compressive failure mechanisms of continuous fiber reinforced polymer composites were discussed according to fiber microbuckling model, fiber kink-band model, combined model and progressive damage failure model. On the basis of the combined prediction model, the effects of carbon fiber (monofilament diameter, elastic modulus, volume fraction, initial deflection angle), polymer matrix (elastic modulus and shear modulus) and fiber/polymer interface on compressive strength and failure mode of continuous fiber reinforced polymer composite were investigated.
Based on the demand of the third generation of advanced composites characterized by high strength, high toughness, high modulus and the balance of compressive and tensile strength, the development history of prediction model of continuous fiber reinforced polymer composite compressive strength was reviewed. The compressive failure mechanisms of continuous fiber reinforced polymer composites were discussed according to fiber microbuckling model, fiber kink-band model, combined model and progressive damage failure model. On the basis of the combined prediction model, the effects of carbon fiber (monofilament diameter, elastic modulus, volume fraction, initial deflection angle), polymer matrix (elastic modulus and shear modulus) and fiber/polymer interface on compressive strength and failure mode of continuous fiber reinforced polymer composite were investigated.
2020, 37(1): 16-26.
doi: 10.13801/j.cnki.fhclxb.20190929.003
Abstract:
The fiber reinforced resin composites have enormous development potentials in the field of deep-sea submersible equipment, and become key strategic materials owing to their light-mass and excellent mechanical properties. It should be noted that the pressure shell is an important part to ensure the safety and stability of a deep-sea submersible. Also, it is closely related to the quality requirements and general performances of submersible. This paper mainly focuses on the deep-sea fiber reinforced resin cylindrical pressure shells. In detail, the structural design characteristics, mechanics performance testing and numerical simulations were reviewed. Moreover, the existing problems were pointed out, and it is expected that these can provide the selection basis for the design and mechanical analysis of the deep-sea cylindrical pressure shells in the future.
The fiber reinforced resin composites have enormous development potentials in the field of deep-sea submersible equipment, and become key strategic materials owing to their light-mass and excellent mechanical properties. It should be noted that the pressure shell is an important part to ensure the safety and stability of a deep-sea submersible. Also, it is closely related to the quality requirements and general performances of submersible. This paper mainly focuses on the deep-sea fiber reinforced resin cylindrical pressure shells. In detail, the structural design characteristics, mechanics performance testing and numerical simulations were reviewed. Moreover, the existing problems were pointed out, and it is expected that these can provide the selection basis for the design and mechanical analysis of the deep-sea cylindrical pressure shells in the future.
2020, 37(1): 27-34.
doi: 10.13801/j.cnki.fhclxb.20190409.001
Abstract:
The surface-modified hollow glass beads with reduced graphene oxide (rGO@HGB) were prepared by electrostatic self-assembly method and then blended with conductive carbon black (CB), graphene nanoplates (GNPs) and epoxy resin (EP), and were further used to prepare CB-GNPs-rGO@HGB/EP composites. The microstructure, conductivity properties and dielectric properties of the CB-GNPs-rGO@HGB/EPcomposites were systematically studied. The results show that rGO@HGB can significantly improve the electrical conductivity and dielectric constant of rGO@HGB/EP composites. After further addition of CB and GNPs, a segregated conductive percolation network is formed by rGO@HGB. There are efficient synergistic effects of rGO, CB and GNPs on improving the properties of CB-GNPs-rGO@HGB/EP composites. With 0.2vol% CB-GNPs at the volume ratio of 10:1, the properties of CB-GNPs-rGO@HGB/EP composites are optimal with the volume resistivity of 1.88×104 Ωcm and the dielectric constant of 454.5 at 1 kHz, which is 11.3% and 10.7% higher than that of CB-rGO@HGB/EP and GNPs-rGO@HGB/EP composites, respectively, while the dielectric loss is only 0.065.
The surface-modified hollow glass beads with reduced graphene oxide (rGO@HGB) were prepared by electrostatic self-assembly method and then blended with conductive carbon black (CB), graphene nanoplates (GNPs) and epoxy resin (EP), and were further used to prepare CB-GNPs-rGO@HGB/EP composites. The microstructure, conductivity properties and dielectric properties of the CB-GNPs-rGO@HGB/EPcomposites were systematically studied. The results show that rGO@HGB can significantly improve the electrical conductivity and dielectric constant of rGO@HGB/EP composites. After further addition of CB and GNPs, a segregated conductive percolation network is formed by rGO@HGB. There are efficient synergistic effects of rGO, CB and GNPs on improving the properties of CB-GNPs-rGO@HGB/EP composites. With 0.2vol% CB-GNPs at the volume ratio of 10:1, the properties of CB-GNPs-rGO@HGB/EP composites are optimal with the volume resistivity of 1.88×104 Ωcm and the dielectric constant of 454.5 at 1 kHz, which is 11.3% and 10.7% higher than that of CB-rGO@HGB/EP and GNPs-rGO@HGB/EP composites, respectively, while the dielectric loss is only 0.065.
Preparation and properties of kaolin grafted alkyl amine type dripping agent/polyethylene composites
2020, 37(1): 35-41.
doi: 10.13801/j.cnki.fhclxb.20190416.002
Abstract:
The eighteen alkyl diethanolamine acrylic monoester dripping agent (AAM) was grafted onto kaolin (Ka) by surface grafting, the grafting of AAM and Ka (Ka-g-AAM) was prepared. Then Ka-g-AAM/linear low density polyethylene (LLDPE) composites were prepared by melt extrusion. The structure and properties of Ka-g-AAM/LLDPE were investigated by FTIR, SEM, DSC and acceleration dripping testing etc. The results indicate that AAM is grafted onto the surface of Ka. Compared with AAM/LLDPE and Ka-AAM/LLDPE composite, Ka-g-AAM/LLDPE composites have inconspicuous changes on the melting temperature, the crystallization temperature and mechanical properties. The acceleration dripping duration of Ka-g-AAM/LLDPE composite films is 23 days at 60℃, which is 4 days longer than that of AAM/LLDPE composite.
The eighteen alkyl diethanolamine acrylic monoester dripping agent (AAM) was grafted onto kaolin (Ka) by surface grafting, the grafting of AAM and Ka (Ka-g-AAM) was prepared. Then Ka-g-AAM/linear low density polyethylene (LLDPE) composites were prepared by melt extrusion. The structure and properties of Ka-g-AAM/LLDPE were investigated by FTIR, SEM, DSC and acceleration dripping testing etc. The results indicate that AAM is grafted onto the surface of Ka. Compared with AAM/LLDPE and Ka-AAM/LLDPE composite, Ka-g-AAM/LLDPE composites have inconspicuous changes on the melting temperature, the crystallization temperature and mechanical properties. The acceleration dripping duration of Ka-g-AAM/LLDPE composite films is 23 days at 60℃, which is 4 days longer than that of AAM/LLDPE composite.
2020, 37(1): 42-49.
doi: 10.13801/j.cnki.fhclxb.20190509.003
Abstract:
The bisphenol A cyanate ester(BCE) was modified by 4,5-epoxyhexane-1,2-dicarboxylic acid diglycidyl ester(TDE-85), phenyl glycidyl ether(PGE) and nonylphenol (NP) (TPNCE), and high strength and high modulus polyimide fiber/TPNCE(PI/TPNCE) composites were prepared by wet winding and autoclave molding process. The mechanical properties and dielectric properties of TPNCE resin and PI/TPNCE composites were analyzed. The results show that the impact strength of TPNCE resin reaches 14.2 kJ/m2, which is nearly double that of the BCE. Compared with the unmodified system, the TPNCE resin keep excellent dielectric properties, the curing temperature drops by about 43℃, and the interface is better with PI fiber. In addition, the PI/TPNCE composite has 0°tensile strength of 1485 MPa, bending strength of 758 MPa, compressive strength of 322 MPa, dielectric constant of about 3.15 and dielectric loss factor of 0.005-0.0075 at 7-18 GHz. The glass transition temperature of PI/TPNCE composite is 197℃ and density is 1.28 g/cm3. This study realizes an important breakthrough in the combination of high-strength and high-modulus PI fiber and cyanate ester, and provides a new idea for the design and material selection of lightweight high-strength structural-functional integrated composites.
The bisphenol A cyanate ester(BCE) was modified by 4,5-epoxyhexane-1,2-dicarboxylic acid diglycidyl ester(TDE-85), phenyl glycidyl ether(PGE) and nonylphenol (NP) (TPNCE), and high strength and high modulus polyimide fiber/TPNCE(PI/TPNCE) composites were prepared by wet winding and autoclave molding process. The mechanical properties and dielectric properties of TPNCE resin and PI/TPNCE composites were analyzed. The results show that the impact strength of TPNCE resin reaches 14.2 kJ/m2, which is nearly double that of the BCE. Compared with the unmodified system, the TPNCE resin keep excellent dielectric properties, the curing temperature drops by about 43℃, and the interface is better with PI fiber. In addition, the PI/TPNCE composite has 0°tensile strength of 1485 MPa, bending strength of 758 MPa, compressive strength of 322 MPa, dielectric constant of about 3.15 and dielectric loss factor of 0.005-0.0075 at 7-18 GHz. The glass transition temperature of PI/TPNCE composite is 197℃ and density is 1.28 g/cm3. This study realizes an important breakthrough in the combination of high-strength and high-modulus PI fiber and cyanate ester, and provides a new idea for the design and material selection of lightweight high-strength structural-functional integrated composites.
2020, 37(1): 50-56.
doi: 10.13801/j.cnki.fhclxb.20190425.001
Abstract:
The halloysite nanotubes/waterborne polyurethane (HNTs/WPU) composite film was synthesized by both in-situ polymerization and surface fluorination method. The effects of the content of amine-modified halloysite nanotubes(AHNTs) and the modification of fluoroalkylsilane(FAS) on the properties of AHNTs/WPU composite film were also investigated. The results show that the mechanical properties and thermal resistance of the AHNTs/WPU composite film increase first and then decrease with the increase of the mass ratio of AHNTs to WPU, and the hydrophobicity improve. When the mass ratio of AHNTs to WPU is 1.5%, the AHNTs/WPU composite film has better comprehensive properties. The tensile strength of the AHNTs/WPU composite film increases by 50% and the elongation at break increases by 35%; the initial thermal degradation temperature (Td5) increases by 9℃ comparing with pure WPU. The water absorption ratio of the AHNTs/WPU composite film decreases to 5.8%, the water contact angle increases to 95.1°. After fluorination of the AHNTs/WPU composite film, the water contact angle of the composite film is 114.5°. The AHNTs/WPU composite film shows hydrophobicity. The surface fluorination treatment has significant effect on the mechanical properties and water absorption ratio of the AHNTs/WPU composite film.
The halloysite nanotubes/waterborne polyurethane (HNTs/WPU) composite film was synthesized by both in-situ polymerization and surface fluorination method. The effects of the content of amine-modified halloysite nanotubes(AHNTs) and the modification of fluoroalkylsilane(FAS) on the properties of AHNTs/WPU composite film were also investigated. The results show that the mechanical properties and thermal resistance of the AHNTs/WPU composite film increase first and then decrease with the increase of the mass ratio of AHNTs to WPU, and the hydrophobicity improve. When the mass ratio of AHNTs to WPU is 1.5%, the AHNTs/WPU composite film has better comprehensive properties. The tensile strength of the AHNTs/WPU composite film increases by 50% and the elongation at break increases by 35%; the initial thermal degradation temperature (Td5) increases by 9℃ comparing with pure WPU. The water absorption ratio of the AHNTs/WPU composite film decreases to 5.8%, the water contact angle increases to 95.1°. After fluorination of the AHNTs/WPU composite film, the water contact angle of the composite film is 114.5°. The AHNTs/WPU composite film shows hydrophobicity. The surface fluorination treatment has significant effect on the mechanical properties and water absorption ratio of the AHNTs/WPU composite film.
2020, 37(1): 57-66.
doi: 10.13801/j.cnki.fhclxb.20190412.005
Abstract:
The three different kinds of nano montmorillonites (nMMT) (Na-montmorillonite(Na-MMT), nMMT modified by amino acid(OMMT-A), and nMMT modified by CH3(CH2)17N(CH3)[(CH2CH2OH)2]+(OMMT-B)) were added into the polyamide 6-66 (PA6-66) matrix through melt blending to prepare different nano montmorillonite/polyamide 6-66 (nMMT/PA6-66) composites. The effects of different surface modified nMMTs on crystallization behaviors, rheology properties and mechanical properties of PA6-66 were investigated. It is observed that nMMTs can promote the formation of γ-crystal and increase the crystallization temperature of nMMT/PA6-66 composites, but the efficiency of heterogeneous nucleation of OMMT-B decreases to a certain extent. Simultaneously, OMMT-B has better ability to improve the storage modulus and flow ability of PA6-66 compared with other two nMMTs. The mechanical properties results show that nMMTs can increase the strength and decrease the toughness of PA6-66, but the effects are different. Among these composites, the nMMT/PA6-66 composite incorporated with OMMT-B has the best mechanical performance, not only the tensile strength and the flexural strength are raise 26% and 28% compare with the pure PA6-66, respectively; but also the toughness is close to unchanged. Based on the comprehensive results, the effects of different surface modified nMMTs on the properties of PA6-66 have been studied systemic, which is mainly depends on the interaction between the organic modifier of nMMT and PA6-66 molecular chains.
The three different kinds of nano montmorillonites (nMMT) (Na-montmorillonite(Na-MMT), nMMT modified by amino acid(OMMT-A), and nMMT modified by CH3(CH2)17N(CH3)[(CH2CH2OH)2]+(OMMT-B)) were added into the polyamide 6-66 (PA6-66) matrix through melt blending to prepare different nano montmorillonite/polyamide 6-66 (nMMT/PA6-66) composites. The effects of different surface modified nMMTs on crystallization behaviors, rheology properties and mechanical properties of PA6-66 were investigated. It is observed that nMMTs can promote the formation of γ-crystal and increase the crystallization temperature of nMMT/PA6-66 composites, but the efficiency of heterogeneous nucleation of OMMT-B decreases to a certain extent. Simultaneously, OMMT-B has better ability to improve the storage modulus and flow ability of PA6-66 compared with other two nMMTs. The mechanical properties results show that nMMTs can increase the strength and decrease the toughness of PA6-66, but the effects are different. Among these composites, the nMMT/PA6-66 composite incorporated with OMMT-B has the best mechanical performance, not only the tensile strength and the flexural strength are raise 26% and 28% compare with the pure PA6-66, respectively; but also the toughness is close to unchanged. Based on the comprehensive results, the effects of different surface modified nMMTs on the properties of PA6-66 have been studied systemic, which is mainly depends on the interaction between the organic modifier of nMMT and PA6-66 molecular chains.
2020, 37(1): 67-73.
doi: 10.13801/j.cnki.fhclxb.20190412.002
Abstract:
Because of its excellent mechanical properties and reinforcing ability, microfibrillated cellulose (MFC) has become a promising candidate for developing nanocomposite. However MFC was easy to agglomerate, which affected its enhancement ability. In this study, MFC was pretreated by freeze-drying(FDMFC). Then FDMFC and linear low density polyethylene (LLDPE) were melted and compounded by a micro-cone twin screw extruder, and the FDMFC/LLDPE composite film was prepared by hot pressing-cold pressing method. The tensile property, dynamic thermomechanical performance (DMA), thermal decomposition process and dispersibility of FDMFC/LLDPE composite were evaluated. The results show that freeze-drying make FDMFC uniformly disperse in LLDPE matrix comparing with the untreated MFC. A reasonable amount of FDMFC can effectively improve the tensile property of FDMFC/LLDPE composite. When adding 10wt% FDMFC, the FDMFC/LLDPE composite increases by 60.3% in tensile strength and 161.9% in Young's modulus comparing to LLDPE. DMA test results show that both storage modulus and loss modulus of the FDMFC/LLDPE composite are improved with the increase of FDMFC content. Thermal analysis indicates that FDMFC can increase the pyrolysis temperature of the FDMFC/LLDPE composite film, and the maximum pyrolysis temperature increases by 14℃ comparing to LLDPE.
Because of its excellent mechanical properties and reinforcing ability, microfibrillated cellulose (MFC) has become a promising candidate for developing nanocomposite. However MFC was easy to agglomerate, which affected its enhancement ability. In this study, MFC was pretreated by freeze-drying(FDMFC). Then FDMFC and linear low density polyethylene (LLDPE) were melted and compounded by a micro-cone twin screw extruder, and the FDMFC/LLDPE composite film was prepared by hot pressing-cold pressing method. The tensile property, dynamic thermomechanical performance (DMA), thermal decomposition process and dispersibility of FDMFC/LLDPE composite were evaluated. The results show that freeze-drying make FDMFC uniformly disperse in LLDPE matrix comparing with the untreated MFC. A reasonable amount of FDMFC can effectively improve the tensile property of FDMFC/LLDPE composite. When adding 10wt% FDMFC, the FDMFC/LLDPE composite increases by 60.3% in tensile strength and 161.9% in Young's modulus comparing to LLDPE. DMA test results show that both storage modulus and loss modulus of the FDMFC/LLDPE composite are improved with the increase of FDMFC content. Thermal analysis indicates that FDMFC can increase the pyrolysis temperature of the FDMFC/LLDPE composite film, and the maximum pyrolysis temperature increases by 14℃ comparing to LLDPE.
2020, 37(1): 74-81.
doi: 10.13801/j.cnki.fhclxb.20190412.004
Abstract:
The hydroxylated multi-walled carbon nanotubes (MWCNTs-OH) initiated the ring-opening polymerization of ε-caprolactone (ε-CL), and polycaprolactone (PCL) grafted MWCNTs-OH (MWCNTs-OH-g-PCL) was prepared. The MWCNTs-OH-g-PCL/poly(L-lactic acid) (PLLA) composites were obtained by solution blending which had different contents of MWCNTs-OH-g-PCL. The grafted product was characterized by FTIR. It is found that MWCNTs-OH-g-PCL exhibits a carbonyl (C=O) stretching vibration peak in PCL at near 1 720 cm-1, indicating that the grafted product is synthesized successfully. The effects of MWCNTs-OH-g-PCL on the crystallization behavior and thermal stability of PLLA homopolymers were investigated by DSC, polarized optical microscope (POM) and TGA. The results show that the crystallinity and the optimum temperaturerate of isothermal crystallization of the MWCNTs-OH-g-PCL/PLLA composites increase by the heterogeneous nucleation of MWCNTs-OH-g-PCL and the plasticization of PCL. The results also show that the grafting amounts of PCL in the MWCNTs-OH-g-PCL is 66%, and the decomposition temperature of the MWCNTs-OH-g-PCL/PLLA composites increases by about 30℃.
The hydroxylated multi-walled carbon nanotubes (MWCNTs-OH) initiated the ring-opening polymerization of ε-caprolactone (ε-CL), and polycaprolactone (PCL) grafted MWCNTs-OH (MWCNTs-OH-g-PCL) was prepared. The MWCNTs-OH-g-PCL/poly(L-lactic acid) (PLLA) composites were obtained by solution blending which had different contents of MWCNTs-OH-g-PCL. The grafted product was characterized by FTIR. It is found that MWCNTs-OH-g-PCL exhibits a carbonyl (C=O) stretching vibration peak in PCL at near 1 720 cm-1, indicating that the grafted product is synthesized successfully. The effects of MWCNTs-OH-g-PCL on the crystallization behavior and thermal stability of PLLA homopolymers were investigated by DSC, polarized optical microscope (POM) and TGA. The results show that the crystallinity and the optimum temperaturerate of isothermal crystallization of the MWCNTs-OH-g-PCL/PLLA composites increase by the heterogeneous nucleation of MWCNTs-OH-g-PCL and the plasticization of PCL. The results also show that the grafting amounts of PCL in the MWCNTs-OH-g-PCL is 66%, and the decomposition temperature of the MWCNTs-OH-g-PCL/PLLA composites increases by about 30℃.
2020, 37(1): 82-88.
doi: 10.13801/j.cnki.fhclxb.20190412.001
Abstract:
In order to investigate the resistance characteristics of unidirectional carbon fiber/epoxy prepreg subjected to lightning currents, low simulated lightning currents of 10/350 μs waveform were applied on the unidirectional carbon fiber/epoxy prepreg. The direct current (DC) resistance data of the unidirectional carbon fiber/epoxy prepreg before and after the tests were measured adopting the four-probe method. The SEM and Raman spectrum were used to characterize the morphology and phase structure of carbon fiber/epoxy prepreg before and after the test. The causes of the DC resistance change were analyzed. The results show that the DC resistance of the carbon fiber/epoxy prepreg does not change monotonously with the increase of lightning current, but tends to decrease first and then increase. This trend is the combined effects of graphitization, epoxy insulation deterioration, fiber fracture and tunnel effect.
In order to investigate the resistance characteristics of unidirectional carbon fiber/epoxy prepreg subjected to lightning currents, low simulated lightning currents of 10/350 μs waveform were applied on the unidirectional carbon fiber/epoxy prepreg. The direct current (DC) resistance data of the unidirectional carbon fiber/epoxy prepreg before and after the tests were measured adopting the four-probe method. The SEM and Raman spectrum were used to characterize the morphology and phase structure of carbon fiber/epoxy prepreg before and after the test. The causes of the DC resistance change were analyzed. The results show that the DC resistance of the carbon fiber/epoxy prepreg does not change monotonously with the increase of lightning current, but tends to decrease first and then increase. This trend is the combined effects of graphitization, epoxy insulation deterioration, fiber fracture and tunnel effect.
2020, 37(1): 89-95.
doi: 10.13801/j.cnki.fhclxb.20190318.001
Abstract:
The aramid fiber-reinforced polymer(AFRP) composite are proverbial difficult-to-machining materials, it is easy to generate defects of burr and ablation. At present, there is lacks of the effective processing methods for AFRP composite. In order to raise processing quality, the drilling experiment of AFRP composite using liquid nitrogen as cooling medium was studied. A comparative test of dry cutting and cryogenic machining under the same cutting parameters was carried out. The axial cutting force and temperature in the vicinity of the hole in the cutting process were measured, and the delamination factor and fuzzing area after drilling were calculated. The causes of AFRP composite machining defects were analyzed, and the changing rules of defects under different cutting conditions were discussed. The results show that compared with dry cutting, the cutting force increases by 15.2%, the cutting temperature decreases by 141.6℃, and the burr area decreases by 24.7%. The ablation phenomenon caused by cutting heat is inhibited, visibly improving the processing quality of AFRP composite when liquid nitrogen ultralow temperature cooling is used.
The aramid fiber-reinforced polymer(AFRP) composite are proverbial difficult-to-machining materials, it is easy to generate defects of burr and ablation. At present, there is lacks of the effective processing methods for AFRP composite. In order to raise processing quality, the drilling experiment of AFRP composite using liquid nitrogen as cooling medium was studied. A comparative test of dry cutting and cryogenic machining under the same cutting parameters was carried out. The axial cutting force and temperature in the vicinity of the hole in the cutting process were measured, and the delamination factor and fuzzing area after drilling were calculated. The causes of AFRP composite machining defects were analyzed, and the changing rules of defects under different cutting conditions were discussed. The results show that compared with dry cutting, the cutting force increases by 15.2%, the cutting temperature decreases by 141.6℃, and the burr area decreases by 24.7%. The ablation phenomenon caused by cutting heat is inhibited, visibly improving the processing quality of AFRP composite when liquid nitrogen ultralow temperature cooling is used.
2020, 37(1): 96-103.
doi: 10.13801/j.cnki.fhclxb.20190416.001
Abstract:
The aramid fibrid-polydopamine/polyimide-phenolic resin (AF-PDA/PI-PF) composite films with 15wt% AF and 7.5wt% PDA were prepared by wet forming and hot-pressing curing technique using PDA modified PI fiber and PF as the matrix with the introduction of AF as reinforcement. The effects of the addition of AF and PDA modification on the mechanical properties and friction and wear properties of PI-PF composite films and wear mechanism were mainly studied. The results show that when adding AF and using PDA modified PI fiber simultaneously, the stress, the tensile index and the interlayer bonding strength of AF-PDA/PI-PF composite films are 47.54 MPa, 56.91 Nmg-1 and 1 265.6 Jm-2, respectively, which increase by 33.65%, 41.67% and 64.11% compared with PI-PF composite films. The wear rate of AF-PDA/PI-PF composite films is 1.01×10-4 mm3 J-1, which is 34.84% lower than PI-PF composite films. The main wear mechanism of AF-PDA/PI-PF composite films is proposed to be adhesive wear. The PI fiber and AF can form "interpenetrating networks" structure, and the PDA modification of PI fiber improves the surface activity of PI fiber, which plays a synergistic role in improving the interfacial bonding strength between PI fiber and PF, as well as the mechanical properties and friction and wear properties of AF-PDA/PI-PF composite films.
The aramid fibrid-polydopamine/polyimide-phenolic resin (AF-PDA/PI-PF) composite films with 15wt% AF and 7.5wt% PDA were prepared by wet forming and hot-pressing curing technique using PDA modified PI fiber and PF as the matrix with the introduction of AF as reinforcement. The effects of the addition of AF and PDA modification on the mechanical properties and friction and wear properties of PI-PF composite films and wear mechanism were mainly studied. The results show that when adding AF and using PDA modified PI fiber simultaneously, the stress, the tensile index and the interlayer bonding strength of AF-PDA/PI-PF composite films are 47.54 MPa, 56.91 Nmg-1 and 1 265.6 Jm-2, respectively, which increase by 33.65%, 41.67% and 64.11% compared with PI-PF composite films. The wear rate of AF-PDA/PI-PF composite films is 1.01×10-4 mm3 J-1, which is 34.84% lower than PI-PF composite films. The main wear mechanism of AF-PDA/PI-PF composite films is proposed to be adhesive wear. The PI fiber and AF can form "interpenetrating networks" structure, and the PDA modification of PI fiber improves the surface activity of PI fiber, which plays a synergistic role in improving the interfacial bonding strength between PI fiber and PF, as well as the mechanical properties and friction and wear properties of AF-PDA/PI-PF composite films.
2020, 37(1): 104-112.
doi: 10.13801/j.cnki.fhclxb.20190517.002
Abstract:
The flexural properties of carbon fiber/epoxy (T700/TR1219B) composite were investigated under different hygrothermal conditions, including single moisture, temperature and coupled moisture-temperature conditions. Combined with fracture morphology and surface roughness, the degradation mechanism was analyzed. The experimental results show that the flexural properties decrease significantly under hygrothermal conditions. With the moisture absorption rate of 2%, the flexural strength decreases sharply from 1 440.60 MPa to 1 081.07 MPa due to the interfacial debonding caused by water absorption. The flexural properties decrease with temperature increasing and exhibit a steep fall in the range of glass transition temperature Tg. The flexural modulus and flexural strength decrease by 71.18% and 93.32% at 180℃, respectively, caused by resin degradation under high temperature. The coupled moisture-temperature condition results in the steep fall of properties at lower temperature range. The residual strength model is established and verified concerning the effects of hygrothermal conditions. The life-time estimation of T700/TR1219B composite is realized by introducing the aging time and environmental equivalence.
The flexural properties of carbon fiber/epoxy (T700/TR1219B) composite were investigated under different hygrothermal conditions, including single moisture, temperature and coupled moisture-temperature conditions. Combined with fracture morphology and surface roughness, the degradation mechanism was analyzed. The experimental results show that the flexural properties decrease significantly under hygrothermal conditions. With the moisture absorption rate of 2%, the flexural strength decreases sharply from 1 440.60 MPa to 1 081.07 MPa due to the interfacial debonding caused by water absorption. The flexural properties decrease with temperature increasing and exhibit a steep fall in the range of glass transition temperature Tg. The flexural modulus and flexural strength decrease by 71.18% and 93.32% at 180℃, respectively, caused by resin degradation under high temperature. The coupled moisture-temperature condition results in the steep fall of properties at lower temperature range. The residual strength model is established and verified concerning the effects of hygrothermal conditions. The life-time estimation of T700/TR1219B composite is realized by introducing the aging time and environmental equivalence.
2020, 37(1): 113-120.
doi: 10.13801/j.cnki.fhclxb.20190403.001
Abstract:
Micro damage in composites usually leads to catastrophic failures in the following applications and therefore needs to be detected. However, it is difficult to detect transverse cracks in composite laminates by using ultrasonic nondestructive testing. In this research, a highly-sensitive and broad bandwidth phase-shifted fiber Bragg grating ultrasonic sensing system was developed and applied to detect Lamb wave propagating in a cross-ply carbon fiber reinforced polymer composites. After conducting data process on the detected Lamb wave, it is found that along the increase of crack numbers induced by the standard three-point bending test, the amplitude of the waveform and the peak value of the spectrum both linearly decrease. After compared with conventional lead-zirconate-titanate sensor, all research results demonstrate that the Lamb wave detected by phase-shifted fiber Bragg grating sensor shows a higher declining rate when the number of matrix cracks increase. Thus, the novel optical-fiber-based sensor succeeds in detection of weak ultrasonic signals with middle frequency of 300 kHz, and can precisely evaluate the micro transverse cracks in composite laminate.
Micro damage in composites usually leads to catastrophic failures in the following applications and therefore needs to be detected. However, it is difficult to detect transverse cracks in composite laminates by using ultrasonic nondestructive testing. In this research, a highly-sensitive and broad bandwidth phase-shifted fiber Bragg grating ultrasonic sensing system was developed and applied to detect Lamb wave propagating in a cross-ply carbon fiber reinforced polymer composites. After conducting data process on the detected Lamb wave, it is found that along the increase of crack numbers induced by the standard three-point bending test, the amplitude of the waveform and the peak value of the spectrum both linearly decrease. After compared with conventional lead-zirconate-titanate sensor, all research results demonstrate that the Lamb wave detected by phase-shifted fiber Bragg grating sensor shows a higher declining rate when the number of matrix cracks increase. Thus, the novel optical-fiber-based sensor succeeds in detection of weak ultrasonic signals with middle frequency of 300 kHz, and can precisely evaluate the micro transverse cracks in composite laminate.
2020, 37(1): 121-131.
doi: 10.13801/j.cnki.fhclxb.20190308.001
Abstract:
The experimental tensile tests have been performed on adhesively bonded single-lap joints of carbon fiber reinforced polymer(CFRP) composite laminates with different lap lengths and stacking sequences. The relevant mechanical responses and damage behaviors were observed during the test process. Finite element (FE) models were built, in which the intralaminar damage was captured using the continuum damage mechanics (CDM) theory derived from 3D Hashin damage criteria, and the delamination of CFRP composite laminates as well as the failure of adhesive were simulated by cohesive zone model (CZM). The numerical prediction is in a good agreement with the experimental results, which validates the numerical modeling strategy. The effect of lap length and stacking sequence on the bonding strength and damage behaviors was investigated for adhesively bonded joints with single-lap and double-lap configurations. The optimization configuration was obtained using the numerical simulation for adhesively bonded joint of CFRP composite laminates. The results show that the ultimate failure load rises with the increase of the lap length for both single-lap and double-lap configurations, and it finally tends to be a stable value. The failure modes of the joints gradually transform from the shear failure within adhesive film to the delamination within laminates adjacent to the ahesive film. The bonding strength and failure modes also change as the stacking sequence varies, and the optimal stacking sequence is obtained as[03/903]2 s by comparing and analysing three stacking sequences. When the lap length varies in the range of 5-20 mm, the optimum is obtained as 17 mm for single-lap configuration, and that value is 19.3 mm in the double-lap case. Compared with joint with the lap length of 20 mm, the bonding strengths of adhesively bonding single-lap and double-lap joints are increased by 13.26% and 0.43%, respectively.
The experimental tensile tests have been performed on adhesively bonded single-lap joints of carbon fiber reinforced polymer(CFRP) composite laminates with different lap lengths and stacking sequences. The relevant mechanical responses and damage behaviors were observed during the test process. Finite element (FE) models were built, in which the intralaminar damage was captured using the continuum damage mechanics (CDM) theory derived from 3D Hashin damage criteria, and the delamination of CFRP composite laminates as well as the failure of adhesive were simulated by cohesive zone model (CZM). The numerical prediction is in a good agreement with the experimental results, which validates the numerical modeling strategy. The effect of lap length and stacking sequence on the bonding strength and damage behaviors was investigated for adhesively bonded joints with single-lap and double-lap configurations. The optimization configuration was obtained using the numerical simulation for adhesively bonded joint of CFRP composite laminates. The results show that the ultimate failure load rises with the increase of the lap length for both single-lap and double-lap configurations, and it finally tends to be a stable value. The failure modes of the joints gradually transform from the shear failure within adhesive film to the delamination within laminates adjacent to the ahesive film. The bonding strength and failure modes also change as the stacking sequence varies, and the optimal stacking sequence is obtained as[03/903]2 s by comparing and analysing three stacking sequences. When the lap length varies in the range of 5-20 mm, the optimum is obtained as 17 mm for single-lap configuration, and that value is 19.3 mm in the double-lap case. Compared with joint with the lap length of 20 mm, the bonding strengths of adhesively bonding single-lap and double-lap joints are increased by 13.26% and 0.43%, respectively.
2020, 37(1): 132-139.
doi: 10.13801/j.cnki.fhclxb.20190324.002
Abstract:
The undulation effect of fiber bundles on plain weave composites causes the variety of slave material principal direction and the concentration of out-of-plane shear stress. A meso-scale finite model based on the improved voxel meshes for a unit cell was utilized to explore the influence on the mechanical properties and damage behavior for plain weave composites. In the model, the variety of slave material principal direction was defined according to the undulated curve of fiber bundles, and a shear correction factor was introduced into Hashin criterion which was used to predict the initial damage of fiber bundles to consider the effect of out-of-plane shear stress on in-plane tensile damage. The model can accurately simulate the in-plane tensile strength and damage process. The results indicate that the undulation of slave material principle direction gives rise to the decline of in-plane tensile strength for plain weave composite. The concentration of out-of-plane shear stress is the main factor leading to the failure of composites, and reduces the tensile strength significantly with the increase of shear correction factor. In addition, both the two factors have affected the damage behavior and failure mechanism of plain weave composites, which need to be expressed accurately in numerical analysis.
The undulation effect of fiber bundles on plain weave composites causes the variety of slave material principal direction and the concentration of out-of-plane shear stress. A meso-scale finite model based on the improved voxel meshes for a unit cell was utilized to explore the influence on the mechanical properties and damage behavior for plain weave composites. In the model, the variety of slave material principal direction was defined according to the undulated curve of fiber bundles, and a shear correction factor was introduced into Hashin criterion which was used to predict the initial damage of fiber bundles to consider the effect of out-of-plane shear stress on in-plane tensile damage. The model can accurately simulate the in-plane tensile strength and damage process. The results indicate that the undulation of slave material principle direction gives rise to the decline of in-plane tensile strength for plain weave composite. The concentration of out-of-plane shear stress is the main factor leading to the failure of composites, and reduces the tensile strength significantly with the increase of shear correction factor. In addition, both the two factors have affected the damage behavior and failure mechanism of plain weave composites, which need to be expressed accurately in numerical analysis.
2020, 37(1): 140-146.
doi: 10.13801/j.cnki.fhclxb.20190314.003
Abstract:
To investigate the degradation mechanism of new material adhesive structures applied to automobile after experiencing continuous high temperature environment, adhesively bonded aluminum alloy-aluminum alloy(Al-Al) and basalt fiber reinforced polymer composite-aluminum alloy(BFRP-Al) single lap joints were manufactured and then were exposed at 80℃ for 0 day, 5 days, 10 days, 15 days. DSC and FTIR were used to analyze the glass transition temperature (Tg) and chemical components changes of the adhesive and BFRP composite after high temperature exposure. The quasi-static state tensile tests were conducted to acquire the failure loads and the failure modes were also analyzed. The results show that the adhesive involves post-curing and oxidation reactions and the BFRP composite involves thermal decomposition and oxidation reactions under the continuous high temperature environment. The failure load of the Al-Al joints constantly increases and the failure mode is cohesive failure before and after aging which is determined by the adhesive. While the failure load of the BFRP-Al joints firstly increases and then decreases and the failure mode is mixed failure of cohesive and fiber tear with different aging time which is affected by the adhesive and BFRP composite together. With the increase of aging time, the area of the BFRP composite tear gets larger and the failure mode tends to be the basalt fiber/resin interface failure which shows that the effect of the degradation of BFRP composite is more and more significant.
To investigate the degradation mechanism of new material adhesive structures applied to automobile after experiencing continuous high temperature environment, adhesively bonded aluminum alloy-aluminum alloy(Al-Al) and basalt fiber reinforced polymer composite-aluminum alloy(BFRP-Al) single lap joints were manufactured and then were exposed at 80℃ for 0 day, 5 days, 10 days, 15 days. DSC and FTIR were used to analyze the glass transition temperature (Tg) and chemical components changes of the adhesive and BFRP composite after high temperature exposure. The quasi-static state tensile tests were conducted to acquire the failure loads and the failure modes were also analyzed. The results show that the adhesive involves post-curing and oxidation reactions and the BFRP composite involves thermal decomposition and oxidation reactions under the continuous high temperature environment. The failure load of the Al-Al joints constantly increases and the failure mode is cohesive failure before and after aging which is determined by the adhesive. While the failure load of the BFRP-Al joints firstly increases and then decreases and the failure mode is mixed failure of cohesive and fiber tear with different aging time which is affected by the adhesive and BFRP composite together. With the increase of aging time, the area of the BFRP composite tear gets larger and the failure mode tends to be the basalt fiber/resin interface failure which shows that the effect of the degradation of BFRP composite is more and more significant.
2020, 37(1): 147-154.
doi: 10.13801/j.cnki.fhclxb.20190425.003
Abstract:
Large deflection dynamic response of fully clamped square and circular (fiber/polymer)-metal laminates subjected to impact loading was studied theoretically. Based on rigid-perfectly plastic assumption and the plastic limit yield condition, theoretical models of the large deflection dynamic response of (fiber/polymer)-metal laminates subjected to mass impact and blast loading were developed and analytical solutions which considered the interaction between bending and stretching were obtained. Furthermore, the membrane model solutions which neglected effect of bending moment were given. The results show that good agreement between theoretical predictions and experimental results is achieved. The theoretical models can predict the maximum deflections of (fiber/polymer)-metal-laminates subjected to mass impact and explosion loading effectively.
Large deflection dynamic response of fully clamped square and circular (fiber/polymer)-metal laminates subjected to impact loading was studied theoretically. Based on rigid-perfectly plastic assumption and the plastic limit yield condition, theoretical models of the large deflection dynamic response of (fiber/polymer)-metal laminates subjected to mass impact and blast loading were developed and analytical solutions which considered the interaction between bending and stretching were obtained. Furthermore, the membrane model solutions which neglected effect of bending moment were given. The results show that good agreement between theoretical predictions and experimental results is achieved. The theoretical models can predict the maximum deflections of (fiber/polymer)-metal-laminates subjected to mass impact and explosion loading effectively.
2020, 37(1): 155-163.
doi: 10.13801/j.cnki.fhclxb.20190417.003
Abstract:
Based on the mechanism of parallel spring system, theoretical and finite element models of honeycomb with parallel design (HPD) were created based on the concept of functional gradient. The effects of graded coefficient on the in-plane mechanical properties of HPD, including deformation mode, plateau stress and energy absorption, were discussed. The results show that variation of graded coefficient can influence the deformation modes of HPD only under dynamic compression. When the graded coefficient is relatively large, parallel design can improve the plateau property of HPD. Meanwhile, the energy absorption of HPD is also improved. This research provides deep insight into the in-plane properties of HPD with different graded coefficients.
Based on the mechanism of parallel spring system, theoretical and finite element models of honeycomb with parallel design (HPD) were created based on the concept of functional gradient. The effects of graded coefficient on the in-plane mechanical properties of HPD, including deformation mode, plateau stress and energy absorption, were discussed. The results show that variation of graded coefficient can influence the deformation modes of HPD only under dynamic compression. When the graded coefficient is relatively large, parallel design can improve the plateau property of HPD. Meanwhile, the energy absorption of HPD is also improved. This research provides deep insight into the in-plane properties of HPD with different graded coefficients.
2020, 37(1): 164-172.
doi: 10.13801/j.cnki.fhclxb.20190505.003
Abstract:
The AZ91 alloy was introduced into SiCP reinforced magnesium alloy(AZ91) (SiCP/AZ91) composites by hot extrusion, and then the AZ91-(SiCP/AZ91) clad plate with the thickness of 2 mm was prepared in present work. After that, the microstructure and mechanical properties of SiCP/AZ91 clad plate influenced by hot rolling were investigated. The results indicate that the rolling formability of SiCP/AZ91 is significantly improved by introducing AZ91 alloy. As compared with AZ91 layer, the SiCP/AZ91 layer possesses much finer grain size and higher hardness. With the increase of rolling deformation amount, the grains in the AZ91-(SiCP/AZ91) clad plate grow up, the amount of precipitated phase decreases accompanied with the increase of its size. All above phenomena account for the decreasing micro-hardness. As compared with the extruded AZ91-(SiCP/AZ91) clad plate, the yield strength of rolled clad plate increases from 272 MPa to 341 MPa and the tensile strength increases from 353 MPa to 404 MPa with the deformation amount of 50%. During the tensile process, the crack initiation and propagation occur preferentially in the SiCP/AZ91 layer due to the interfacial debonding between SiCP and Mg matrix alloy. However, the existence of the AZ91 layer will hinder the propagation of micro-cracks.
The AZ91 alloy was introduced into SiCP reinforced magnesium alloy(AZ91) (SiCP/AZ91) composites by hot extrusion, and then the AZ91-(SiCP/AZ91) clad plate with the thickness of 2 mm was prepared in present work. After that, the microstructure and mechanical properties of SiCP/AZ91 clad plate influenced by hot rolling were investigated. The results indicate that the rolling formability of SiCP/AZ91 is significantly improved by introducing AZ91 alloy. As compared with AZ91 layer, the SiCP/AZ91 layer possesses much finer grain size and higher hardness. With the increase of rolling deformation amount, the grains in the AZ91-(SiCP/AZ91) clad plate grow up, the amount of precipitated phase decreases accompanied with the increase of its size. All above phenomena account for the decreasing micro-hardness. As compared with the extruded AZ91-(SiCP/AZ91) clad plate, the yield strength of rolled clad plate increases from 272 MPa to 341 MPa and the tensile strength increases from 353 MPa to 404 MPa with the deformation amount of 50%. During the tensile process, the crack initiation and propagation occur preferentially in the SiCP/AZ91 layer due to the interfacial debonding between SiCP and Mg matrix alloy. However, the existence of the AZ91 layer will hinder the propagation of micro-cracks.
2020, 37(1): 173-181.
doi: 10.13801/j.cnki.fhclxb.20190417.001
Abstract:
The silk fibroin (SF) nanofibers were prepared by electrospinning with rich domestic silk as raw material and calcium chloride/formic acid as dissolve system. The mesoporous SiO2 nanotubes (MSNTs) were obtained with calcining after coating SiO2 on SF nanofibers templates. Utilizing dynamic covalent bond between aldehyde group (-CHO), which grafting on the wall of MSNTs, and amino group in doxorubicin hydrochloride (DOXHCl), pH-sensitive drug release system was prepared. The microstructure, functionalization of MSNTs and pH-responsive performance of drug loading system were characterized by SEM, TEM, TG, specific surface area (BET) analysis, FTIR and ultraviolet and visible (UV-Vis) spectroscopy. The results show that when SF concentration is 15wt%-17wt%, cylindrical SF fiber templates can be obtained with adjustable diameters ranging from (113±27) nm to (134±32) nm. The wall thickness of MSNTs can be regulated by adjusting the concentration of cetyl trimethyl ammonium bromide (CTAB) in the coating solution. When the concentration of CTAB increases from 1.25 mg/mL to 3.75 mg/mL, the wall thickness of MSNTs increases from 30-39 nm to 63-65 nm, the corresponding specific surface area decreasing from 154 m2/g to 98 m2/g, and the average mesoporous diameter decreasing from 12.5 nm to 10.0 nm. The drug release rate of the MSNTs modified by aldehyde loading with DOXHCl (MSNT-CHO-DOX) reach 23%, 35% and 75% respectively at 100 h when the release is carried out in dipotassium hydrogen phosphate-potassium phosphate monobasic (PB) buffer solution with pH values of 7.4, 6.5 and 5.5, respectively, achieving pH-responsive release of MSNT-CHO-DOX system.
The silk fibroin (SF) nanofibers were prepared by electrospinning with rich domestic silk as raw material and calcium chloride/formic acid as dissolve system. The mesoporous SiO2 nanotubes (MSNTs) were obtained with calcining after coating SiO2 on SF nanofibers templates. Utilizing dynamic covalent bond between aldehyde group (-CHO), which grafting on the wall of MSNTs, and amino group in doxorubicin hydrochloride (DOXHCl), pH-sensitive drug release system was prepared. The microstructure, functionalization of MSNTs and pH-responsive performance of drug loading system were characterized by SEM, TEM, TG, specific surface area (BET) analysis, FTIR and ultraviolet and visible (UV-Vis) spectroscopy. The results show that when SF concentration is 15wt%-17wt%, cylindrical SF fiber templates can be obtained with adjustable diameters ranging from (113±27) nm to (134±32) nm. The wall thickness of MSNTs can be regulated by adjusting the concentration of cetyl trimethyl ammonium bromide (CTAB) in the coating solution. When the concentration of CTAB increases from 1.25 mg/mL to 3.75 mg/mL, the wall thickness of MSNTs increases from 30-39 nm to 63-65 nm, the corresponding specific surface area decreasing from 154 m2/g to 98 m2/g, and the average mesoporous diameter decreasing from 12.5 nm to 10.0 nm. The drug release rate of the MSNTs modified by aldehyde loading with DOXHCl (MSNT-CHO-DOX) reach 23%, 35% and 75% respectively at 100 h when the release is carried out in dipotassium hydrogen phosphate-potassium phosphate monobasic (PB) buffer solution with pH values of 7.4, 6.5 and 5.5, respectively, achieving pH-responsive release of MSNT-CHO-DOX system.
2020, 37(1): 182-190.
doi: 10.13801/j.cnki.fhclxb.20190505.002
Abstract:
The bisphenol A (BPA) is widely used in food packaging materials. It can cause endocrine disorders in human body and lead to abnormal immune and reproductive system, so it is very important to detect BPA in water. In this paper, the ferric oxide-reduced graphene oxide (Fe2O3-rGO) composite was synthesized and characterized by one step hydrothermal method. Based on the Fe2O3-rGO composite, the Fe2O3-rGO/glassy carbon electrode electrochemical sensor was constructed for the detection of BPA in water. The results of FTIR, XRD and SEM show that Fe2O3 nanoparticles are successfully attached to rGO. The electrochemical detection of BPA by differential pulse voltammetry (DPV) shows that the linear range of BPA is 0.1-100 μmol/L and the detection limit is 0.033 μmol/L (signal to noise ratio is 3). Meanwhile, the Fe2O3-rGO/glassy carbon electrode electrochemical sensor has good anti-interference ability to electroactive substances and common metal ions and the real sample detection results are ideal.
The bisphenol A (BPA) is widely used in food packaging materials. It can cause endocrine disorders in human body and lead to abnormal immune and reproductive system, so it is very important to detect BPA in water. In this paper, the ferric oxide-reduced graphene oxide (Fe2O3-rGO) composite was synthesized and characterized by one step hydrothermal method. Based on the Fe2O3-rGO composite, the Fe2O3-rGO/glassy carbon electrode electrochemical sensor was constructed for the detection of BPA in water. The results of FTIR, XRD and SEM show that Fe2O3 nanoparticles are successfully attached to rGO. The electrochemical detection of BPA by differential pulse voltammetry (DPV) shows that the linear range of BPA is 0.1-100 μmol/L and the detection limit is 0.033 μmol/L (signal to noise ratio is 3). Meanwhile, the Fe2O3-rGO/glassy carbon electrode electrochemical sensor has good anti-interference ability to electroactive substances and common metal ions and the real sample detection results are ideal.
2020, 37(1): 191-197.
doi: 10.13801/j.cnki.fhclxb.20190505.004
Abstract:
Glass curtain is foggy and difficult to clean, which increases the cost of wall maintenance. The water-borne polyurethane(PU), hydrophilic SiO2, tetraethyl orthosilicate(TEOS) and ethanol were used as basic materials, and the PU-SiO2 coatings were sprayed on glass curtain wall by spraying process. After curing at room temperature, a transparent PU-SiO2 coating with good wear resistance and fog resistance could be obtained. The surface morphology of the PU-SiO2 coatings was characterized by SEM and the causes of surface wettability were explored through comparative experiments. The principle of superhydrophilicity of the PU-SiO2 coatings was analyzed. The results of wear resistance and fog resistance test show that the PU-SiO2 coating can withstand the maximum pressure of about 26 kPa and has good fog resistance. Ultraviolet-visible spectrophotometer test results show that the PU-SiO2 coating has good transparency. The outdoor experiment shows that the PU-SiO2 coating has good weatherability. The method used in this paper solves the problems of complex process and environmental protection of existing methods, and can be directly applied to the glass curtain wall surface of existing buildings.
Glass curtain is foggy and difficult to clean, which increases the cost of wall maintenance. The water-borne polyurethane(PU), hydrophilic SiO2, tetraethyl orthosilicate(TEOS) and ethanol were used as basic materials, and the PU-SiO2 coatings were sprayed on glass curtain wall by spraying process. After curing at room temperature, a transparent PU-SiO2 coating with good wear resistance and fog resistance could be obtained. The surface morphology of the PU-SiO2 coatings was characterized by SEM and the causes of surface wettability were explored through comparative experiments. The principle of superhydrophilicity of the PU-SiO2 coatings was analyzed. The results of wear resistance and fog resistance test show that the PU-SiO2 coating can withstand the maximum pressure of about 26 kPa and has good fog resistance. Ultraviolet-visible spectrophotometer test results show that the PU-SiO2 coating has good transparency. The outdoor experiment shows that the PU-SiO2 coating has good weatherability. The method used in this paper solves the problems of complex process and environmental protection of existing methods, and can be directly applied to the glass curtain wall surface of existing buildings.
2020, 37(1): 198-204.
doi: 10.13801/j.cnki.fhclxb.20190402.005
Abstract:
In order to accelerate the impact of simulated marine tidal zone environment on the durability of concrete, the mineral powder and nano modified mineral admixture were added, and the effect of dry-wet cycling of NaCl on the resistance to chloride ion erosion and microstructure of concrete was studied, which was compared with the immersion test. The results show that the dry-wet cycling coarsens the pore structure of the concrete surface, increases the pore content of pore size larger than 50 nm and significantly increases the free and total chloride ion concentration; the incorporation of nano-modified mineral admixture can reduce the internal porosity of concrete and the harmful pore content, while can improve the chloride ion binding capacity of concrete. After 60 days of wet and dry cycling, the Ca(OH)2 on the surface layer is gradually consumed, and the Friedel salt and CaCO3 are formed.
In order to accelerate the impact of simulated marine tidal zone environment on the durability of concrete, the mineral powder and nano modified mineral admixture were added, and the effect of dry-wet cycling of NaCl on the resistance to chloride ion erosion and microstructure of concrete was studied, which was compared with the immersion test. The results show that the dry-wet cycling coarsens the pore structure of the concrete surface, increases the pore content of pore size larger than 50 nm and significantly increases the free and total chloride ion concentration; the incorporation of nano-modified mineral admixture can reduce the internal porosity of concrete and the harmful pore content, while can improve the chloride ion binding capacity of concrete. After 60 days of wet and dry cycling, the Ca(OH)2 on the surface layer is gradually consumed, and the Friedel salt and CaCO3 are formed.
2020, 37(1): 205-213.
doi: 10.13801/j.cnki.fhclxb.20190425.002
Abstract:
Based on the tests of five groups of polyvinyl alcohol fiber reinforced engineered cementitious composite (PVA/ECC) specimens, the creep performance of PVA/ECC with different fiber contents under pressure was studied in this paper. The results show that the incorporation of PVA fibers can lower density and elastic modulus of substrate materials and lead to a decline of capacity of resistance to creep. Additionally, within 0-2vol% of volume fraction of PVA fiber, the large or small volume fraction of PVA fiber is found to increase the creep coefficient of PVA/ECC, and the medium volume of PVA fiber can decrease the creep coefficient. The creep speeds of specimens all have a character that increasing rapidly at the initial and then increasing slowly, the creep amount in initial 7 days is about 40% of total amount, that in initial 60 days is about 80% of total amount, and creep amount gradually gets convergent after 60 days. Based on the result of regression analysis to the experimental data, the calculation models of creep coefficient and creep degree of PVA/ECC were presented.
Based on the tests of five groups of polyvinyl alcohol fiber reinforced engineered cementitious composite (PVA/ECC) specimens, the creep performance of PVA/ECC with different fiber contents under pressure was studied in this paper. The results show that the incorporation of PVA fibers can lower density and elastic modulus of substrate materials and lead to a decline of capacity of resistance to creep. Additionally, within 0-2vol% of volume fraction of PVA fiber, the large or small volume fraction of PVA fiber is found to increase the creep coefficient of PVA/ECC, and the medium volume of PVA fiber can decrease the creep coefficient. The creep speeds of specimens all have a character that increasing rapidly at the initial and then increasing slowly, the creep amount in initial 7 days is about 40% of total amount, that in initial 60 days is about 80% of total amount, and creep amount gradually gets convergent after 60 days. Based on the result of regression analysis to the experimental data, the calculation models of creep coefficient and creep degree of PVA/ECC were presented.
2020, 37(1): 214-222.
doi: 10.13801/j.cnki.fhclxb.20190429.001
Abstract:
In order to investigate the alkali resistance of basalt fiber mesh and glass fiber mesh and their influence on the biaxial bending properties of fiber textile reinforced concrete panel, the alkali resistance test of basalt fiber and glass fiber and the biaxial flexural properties of fiber textile reinforced concrete slab were carried out. Based on the two-way slab test in accordance with EFNARC, the biaxial effect of different fiber textile was analyzed. The results show that the corrosion resistance of alkali resistance glass fiber is superior to that of basalt fiber. The high two-way tensile properties of the fiber textile can improve the inner force redistribution and stress redistribution ability of the two-way slab. The incorporation of basalt fiber mesh and alkali-resistant glass fiber mesh improves the bending resistance load capacity of the concrete matrix slab by 48% and 59%, respectively. Besides, the bidirectional reinforcement of alkali-resistant glass fiber mesh is better than basalt fiber mesh.
In order to investigate the alkali resistance of basalt fiber mesh and glass fiber mesh and their influence on the biaxial bending properties of fiber textile reinforced concrete panel, the alkali resistance test of basalt fiber and glass fiber and the biaxial flexural properties of fiber textile reinforced concrete slab were carried out. Based on the two-way slab test in accordance with EFNARC, the biaxial effect of different fiber textile was analyzed. The results show that the corrosion resistance of alkali resistance glass fiber is superior to that of basalt fiber. The high two-way tensile properties of the fiber textile can improve the inner force redistribution and stress redistribution ability of the two-way slab. The incorporation of basalt fiber mesh and alkali-resistant glass fiber mesh improves the bending resistance load capacity of the concrete matrix slab by 48% and 59%, respectively. Besides, the bidirectional reinforcement of alkali-resistant glass fiber mesh is better than basalt fiber mesh.
2020, 37(1): 223-235.
doi: 10.13801/j.cnki.fhclxb.20190511.001
Abstract:
The static bending and free vibration of functionally graded (FG) sandwich microbeams were investigated based on the modified couple stress theory (MCST) and the sinusoidal shear deformation theory. The two types of FG sandwich microbeams were taken into consideration. Governing equations were derived by using the Hamilton' principle. Analytical solutions of bending and vibration with simply supported boundary condition were obtained in the basis of the Navier's solution procedure. The results with general boundary conditions were obtained by using the Ritz method. The numerical results demonstrate that the static and dynamic behavior of FG sandwich microbeams is size-dependent and affected by the microbeam's nondimensional thickness, FG index, the ratio of length to thickness and the structure type. This study may be helpful for the design and performance optimization of the FG sandwich structures.
The static bending and free vibration of functionally graded (FG) sandwich microbeams were investigated based on the modified couple stress theory (MCST) and the sinusoidal shear deformation theory. The two types of FG sandwich microbeams were taken into consideration. Governing equations were derived by using the Hamilton' principle. Analytical solutions of bending and vibration with simply supported boundary condition were obtained in the basis of the Navier's solution procedure. The results with general boundary conditions were obtained by using the Ritz method. The numerical results demonstrate that the static and dynamic behavior of FG sandwich microbeams is size-dependent and affected by the microbeam's nondimensional thickness, FG index, the ratio of length to thickness and the structure type. This study may be helpful for the design and performance optimization of the FG sandwich structures.
