2015 Vol. 32, No. 6
2015, 32(6): 1547-1557.
doi: 10.13801/j.cnki.fhclxb.20150211.003
Abstract:
In order to guide the optimization design of inorganic particles reinforced polymer matrix wear-resistance composites better, a comprehensive review of the effects of composite constituents on wear-resistance performance of composites was introduced. In terms of the constituents of the composites,the factors impacting wear-resistance performances of inorganic particles reinforced polymer matrix composites were classified into five parts: filler content of nano/micro inorganic particle, filler size of nano/micro particle, inorganic particle gradation with different particle sizes, synergetic enhancement of inorganic particle and fiber, inorganic particle surface treatment. The effects of each factor on wear-resistance performances of the composites were evaluated, using the view of energy, which shows the influence of each factor on external impact and friction work absorbed by fracture of internal combination bonds.Both the best particle content and the best particle size where wear-resistance performances of the composites are best are found in the part of review of the first two factors. For microparticle (particle size>50 μm), because the particle content has more influences on the wear-resistance performances of composites than the particle size, the best content should be as high as possible. But for nanoparticle, because the particle size is the key factor that influences the wear-resistance performance of composites, the best particle size should be as low as possible. Moreover, surface modification and gradation of particle can further improve wear-resistance performance of the composites, through developing the best particle content and comprehensive mechanical properties of the composites. Hybrid of inorganic particle and nano fiber can make composites have optimal wear-resistance performance, friction coefficient and good variable load adaptability.
In order to guide the optimization design of inorganic particles reinforced polymer matrix wear-resistance composites better, a comprehensive review of the effects of composite constituents on wear-resistance performance of composites was introduced. In terms of the constituents of the composites,the factors impacting wear-resistance performances of inorganic particles reinforced polymer matrix composites were classified into five parts: filler content of nano/micro inorganic particle, filler size of nano/micro particle, inorganic particle gradation with different particle sizes, synergetic enhancement of inorganic particle and fiber, inorganic particle surface treatment. The effects of each factor on wear-resistance performances of the composites were evaluated, using the view of energy, which shows the influence of each factor on external impact and friction work absorbed by fracture of internal combination bonds.Both the best particle content and the best particle size where wear-resistance performances of the composites are best are found in the part of review of the first two factors. For microparticle (particle size>50 μm), because the particle content has more influences on the wear-resistance performances of composites than the particle size, the best content should be as high as possible. But for nanoparticle, because the particle size is the key factor that influences the wear-resistance performance of composites, the best particle size should be as low as possible. Moreover, surface modification and gradation of particle can further improve wear-resistance performance of the composites, through developing the best particle content and comprehensive mechanical properties of the composites. Hybrid of inorganic particle and nano fiber can make composites have optimal wear-resistance performance, friction coefficient and good variable load adaptability.
2015, 32(6): 1558-1566.
doi: 10.13801/j.cnki.fhclxb.20150130.001
Abstract:
In order to solve the complex nonlinear problem conveniently, the unified nonlinear constitutive model considering strength-differential effects of fiber reinforced resin matrix composites was proposed firstly. Then, the three-dimensional expression form of the constitutive model was deduced ulteriorly on the basis to be appropriate for the development of nonlinear finite element analysis tool. After that, using user-defined subroutine UMAT which was provided by finite element program ABAQUS, elastic-plastic stress analysis program in cases of two-dimensional and three-dimensional was self-compiled. Finally, the prediction and testing results of stress-strain curves for unidirectional composite laminates and angle-ply composite laminates under off-axis tension/compression were compared using the program, the elastic-plastic problems of composite cantilever beams were discussed, and the differences of stress distribution and deflection response between the cases of with and without considering strength-differential effects were analyzed and compared. The results show that using the proposed constitutive model to analyze the elastic-plastic deformation considering tension and compression asymmetric problems is quite efficient. The constitutive model is expected to become the practical numerical analysis tool, thus guides engineering practices.
In order to solve the complex nonlinear problem conveniently, the unified nonlinear constitutive model considering strength-differential effects of fiber reinforced resin matrix composites was proposed firstly. Then, the three-dimensional expression form of the constitutive model was deduced ulteriorly on the basis to be appropriate for the development of nonlinear finite element analysis tool. After that, using user-defined subroutine UMAT which was provided by finite element program ABAQUS, elastic-plastic stress analysis program in cases of two-dimensional and three-dimensional was self-compiled. Finally, the prediction and testing results of stress-strain curves for unidirectional composite laminates and angle-ply composite laminates under off-axis tension/compression were compared using the program, the elastic-plastic problems of composite cantilever beams were discussed, and the differences of stress distribution and deflection response between the cases of with and without considering strength-differential effects were analyzed and compared. The results show that using the proposed constitutive model to analyze the elastic-plastic deformation considering tension and compression asymmetric problems is quite efficient. The constitutive model is expected to become the practical numerical analysis tool, thus guides engineering practices.
2015, 32(6): 1567-1572.
doi: 10.13801/j.cnki.fhclxb.20150417.002
Abstract:
In order to improve the value of recycling utilization of the textile waste rubber powder (TWRP), a series of nylon fiber (NF)/TWRP sound absorption composites were prepared using TWRP and single-hole hollow NF firstly. Then, the properties and microstructure of the composites were measured and analyzed by instruments of dynamic thermo-mechanical analysis apparatus (DMA), scanning electron microscopy (SEM), absorption instrument and electronic fabric tensile tester et al. The results illustrate that the addition of NF leads to the decreasing of the peak value of damping loss factor and the corresponding glass transition temperature of peak value. With the NF content increasing, the peak value of damping loss factor continues to decrease, whereas the glass transition temperature changes little. The hollow fiber network structure formed by NF makes the composite endowed with sound absorption property, and the rigidity and strength of composites have been obviously improved. The higher the NF content is, the more perfect the fiber network structure will be, and the sound absorption properties of composites improve; the higher the stress of composites is, the lower the strain is. When the NF content is 50wt%, the sound absorption coefficient of NF/TWRP composites with the thickness of 1 mm will be up to 0.476 under the frequency of 2 500 Hz. When the NF content increases from 10wt% to 50wt%, the stress of NF/TWRP composites increases from 112.1 MPa to 161.6 MPa, and the corresponding strain varies from 136.6% to 13.2%. The obtained conclusions provide theoretical basis for functional development of sound absorption materials by using TWRP.
In order to improve the value of recycling utilization of the textile waste rubber powder (TWRP), a series of nylon fiber (NF)/TWRP sound absorption composites were prepared using TWRP and single-hole hollow NF firstly. Then, the properties and microstructure of the composites were measured and analyzed by instruments of dynamic thermo-mechanical analysis apparatus (DMA), scanning electron microscopy (SEM), absorption instrument and electronic fabric tensile tester et al. The results illustrate that the addition of NF leads to the decreasing of the peak value of damping loss factor and the corresponding glass transition temperature of peak value. With the NF content increasing, the peak value of damping loss factor continues to decrease, whereas the glass transition temperature changes little. The hollow fiber network structure formed by NF makes the composite endowed with sound absorption property, and the rigidity and strength of composites have been obviously improved. The higher the NF content is, the more perfect the fiber network structure will be, and the sound absorption properties of composites improve; the higher the stress of composites is, the lower the strain is. When the NF content is 50wt%, the sound absorption coefficient of NF/TWRP composites with the thickness of 1 mm will be up to 0.476 under the frequency of 2 500 Hz. When the NF content increases from 10wt% to 50wt%, the stress of NF/TWRP composites increases from 112.1 MPa to 161.6 MPa, and the corresponding strain varies from 136.6% to 13.2%. The obtained conclusions provide theoretical basis for functional development of sound absorption materials by using TWRP.
2015, 32(6): 1573-1580.
doi: 10.13801/j.cnki.fhclxb.20150410.002
Abstract:
Strain invariant failure theory (SIFT) is a new type of strength theory for composites based on physical failure mode, which is applied to the failure analysis of composite structures widely. In order to improve the accuracy of theoretical analysis, SIFT was extended to be used to analyze the static loading compressive progressive failure mechanism and strength for carbon fiber reinforced polymer (CFRP) composite laminate open-hole structures firstly. The implementation methods of developed SIFT include two parts of material strength characterization and structure strength prediction. The structure strength prediction based on the ABAQUS platform and was realized by using the user defined material subroutine (UMAT) wrote by Fortran scripts. Then, the predicted values of SIFT as well as the predicted results of classical composites strength theories such as Tsai-Wu and Hashin theories were compared with the testing results, and the results showed that the accuracy of SIFT prediction was the best. Meanwhile, based on SIFT, the failure mechanisms evolution from initial failure to final failure of AS4/3501-6 laminate open-hole structures under static loading compression were analyzed in details. Finally, the static loading compressive failure mechanisms of AS4/3501-6 laminate open-hole structures predicted by SIFT were compared with testing results. The results show that the progressive failure mechanisms predicted by SIFT agree well with the testing results. The obtained conclusions provide new thoughts for the strength prediction of CFRP structures.
Strain invariant failure theory (SIFT) is a new type of strength theory for composites based on physical failure mode, which is applied to the failure analysis of composite structures widely. In order to improve the accuracy of theoretical analysis, SIFT was extended to be used to analyze the static loading compressive progressive failure mechanism and strength for carbon fiber reinforced polymer (CFRP) composite laminate open-hole structures firstly. The implementation methods of developed SIFT include two parts of material strength characterization and structure strength prediction. The structure strength prediction based on the ABAQUS platform and was realized by using the user defined material subroutine (UMAT) wrote by Fortran scripts. Then, the predicted values of SIFT as well as the predicted results of classical composites strength theories such as Tsai-Wu and Hashin theories were compared with the testing results, and the results showed that the accuracy of SIFT prediction was the best. Meanwhile, based on SIFT, the failure mechanisms evolution from initial failure to final failure of AS4/3501-6 laminate open-hole structures under static loading compression were analyzed in details. Finally, the static loading compressive failure mechanisms of AS4/3501-6 laminate open-hole structures predicted by SIFT were compared with testing results. The results show that the progressive failure mechanisms predicted by SIFT agree well with the testing results. The obtained conclusions provide new thoughts for the strength prediction of CFRP structures.
2015, 32(6): 1581-1589.
doi: 10.13801/j.cnki.fhclxb.20150303.003
Abstract:
In order to make use of the superior photocatalytic activity of TiO2 and the structural properties of montmorillonite (MMT), TiO2/MMT composites were fabricated by hydrolysis precipitation method using MMT as carrier, TiCl4 as raw material and ammonium hydroxide as precipitant firstly. Then, the component, crystal form, structure and morphology were characterized by FTIR, XRD and SEM. Finally, under the irradiation of ultraviolet light, the photocatalysis degradation activity of TiO2/MMT composites with different TiO2 contents for simulation phenol waste water were investigated, and the tracking experiments were conducted for the process of phenol photocatalysis degradation by composites combined with ultraviolet-visible spectra. The results illustrate that TiO2 in the prepared TiO2/MMT composites is anatase phase, and the crystallite dimension on MMT is 7.8 nm. The domain components of interlayer in TiO2/MMT composites are replaced by titanium pillars, and the pillared reaction processes in the interlayer regions. Thus the basic frame of MMT does not change, and TiO2 spreads on the surfaces of MMT. When the initial concentration of phenol is 10 mg/L, the pH of phenol solution is 6 and the ultraviolet irradiation time is 150 min, the degradation rate of 37.5wt% TiO2/MMT composites for phenol is 63%, superior than that of MMT (4.5%) and pure TiO2 (55%), displays that the loading of MMT improves the photocatalytic activity of TiO2.
In order to make use of the superior photocatalytic activity of TiO2 and the structural properties of montmorillonite (MMT), TiO2/MMT composites were fabricated by hydrolysis precipitation method using MMT as carrier, TiCl4 as raw material and ammonium hydroxide as precipitant firstly. Then, the component, crystal form, structure and morphology were characterized by FTIR, XRD and SEM. Finally, under the irradiation of ultraviolet light, the photocatalysis degradation activity of TiO2/MMT composites with different TiO2 contents for simulation phenol waste water were investigated, and the tracking experiments were conducted for the process of phenol photocatalysis degradation by composites combined with ultraviolet-visible spectra. The results illustrate that TiO2 in the prepared TiO2/MMT composites is anatase phase, and the crystallite dimension on MMT is 7.8 nm. The domain components of interlayer in TiO2/MMT composites are replaced by titanium pillars, and the pillared reaction processes in the interlayer regions. Thus the basic frame of MMT does not change, and TiO2 spreads on the surfaces of MMT. When the initial concentration of phenol is 10 mg/L, the pH of phenol solution is 6 and the ultraviolet irradiation time is 150 min, the degradation rate of 37.5wt% TiO2/MMT composites for phenol is 63%, superior than that of MMT (4.5%) and pure TiO2 (55%), displays that the loading of MMT improves the photocatalytic activity of TiO2.
2015, 32(6): 1590-1595.
doi: 10.13801/j.cnki.fhclxb.20150327.001
Abstract:
In order to prepare the nanoparticles filling silicone composites with favorable thermal conductivity, thermal stability, electrical conductivity and flexibility, vinyl terminated polydimethylsiloxane (PDMS) was used as matrix material and carbon coated cobalt nanoparticles (C@Co) was used as filler, C@Co/PDMS composite thermal interface materials were prepared by ground co-blend method firstly. Then, TEM, XRD, Raman, and SEM were employed to investigate the microstructure, phase, degree of graphitization and dispersibility of C@Co. Finally, the effects of C@Co content on thermal conductivity, thermal stability, electrical conductivity and flexibility of composite thermal interface materials were investigated. The results show that the thermal conductivity of the composite thermal interface materials increases with the C@Co content increasing, when the C@Co content is 24wt%, the thermal conductivity of the composite reaches the maximum 1.64 W/(m·K), which is 10.7 times higher than that of neat PDMS. TG analysis indicates that after the addition of 24wt% C@Co, the initial decomposition temperature and final decomposition temperature of composites increase about 70 ℃ and 80 ℃ comparing to that of the neat PDMS respectively, accounting for C@Co can enhance the thermal stability of the composites. With the C@Co content increasing, the electrical conductivity of the composite thermal interface materials increases nonlinearly, and the percolation threshold value of fitting trial and error calculation is 10wt%, which means that when the C@Co content is less than 10wt%, the insulativity of composite is favorable; but when filled with 24wt% C@Co, the electrical conductivity of composite is 9.38×10-3 S·m-1. The hardness of composites is moderate, which is in the range of 17.6-26.8 HA and indicates that the flexibility of the composite is preferable. Therefore, 24wt% C@Co/PDMS composite can not only meet the basic requirements of the electrical properties of thermal interface materials, but also have favorable thermal conductivity, thermal stability and flexibility.
In order to prepare the nanoparticles filling silicone composites with favorable thermal conductivity, thermal stability, electrical conductivity and flexibility, vinyl terminated polydimethylsiloxane (PDMS) was used as matrix material and carbon coated cobalt nanoparticles (C@Co) was used as filler, C@Co/PDMS composite thermal interface materials were prepared by ground co-blend method firstly. Then, TEM, XRD, Raman, and SEM were employed to investigate the microstructure, phase, degree of graphitization and dispersibility of C@Co. Finally, the effects of C@Co content on thermal conductivity, thermal stability, electrical conductivity and flexibility of composite thermal interface materials were investigated. The results show that the thermal conductivity of the composite thermal interface materials increases with the C@Co content increasing, when the C@Co content is 24wt%, the thermal conductivity of the composite reaches the maximum 1.64 W/(m·K), which is 10.7 times higher than that of neat PDMS. TG analysis indicates that after the addition of 24wt% C@Co, the initial decomposition temperature and final decomposition temperature of composites increase about 70 ℃ and 80 ℃ comparing to that of the neat PDMS respectively, accounting for C@Co can enhance the thermal stability of the composites. With the C@Co content increasing, the electrical conductivity of the composite thermal interface materials increases nonlinearly, and the percolation threshold value of fitting trial and error calculation is 10wt%, which means that when the C@Co content is less than 10wt%, the insulativity of composite is favorable; but when filled with 24wt% C@Co, the electrical conductivity of composite is 9.38×10-3 S·m-1. The hardness of composites is moderate, which is in the range of 17.6-26.8 HA and indicates that the flexibility of the composite is preferable. Therefore, 24wt% C@Co/PDMS composite can not only meet the basic requirements of the electrical properties of thermal interface materials, but also have favorable thermal conductivity, thermal stability and flexibility.
2015, 32(6): 1596-1601.
doi: 10.13801/j.cnki.fhclxb.20150325.001
Abstract:
Preparing phase change composites by mixing expanded graphite powders and paraffin can improve the heat transfer performance of the energy storage materials effectively. In order to investigate the thermal conductivity mechanism of expanded graphite/paraffin phase change composites, the calculation method of the effective thermal conductivity coefficients of three scales solid after the mixture of expanded graphite powders and paraffin was put forward. Then, by numerically simulation calculation, the effective thermal conductivity coefficients of expanded graphite/paraffin phase change composites containing expanded graphite thermal conductive particles with different volume fractions and different thermal conductivity coefficients were obtained. The results show that expanded graphite can improve the heat conduction performance of paraffin greatly, and when the volume fraction of expanded graphite is 10%, the effective thermal conductivity coefficient of expanded graphite/paraffin phase change composite is as high as 9 times of the pure paraffin. In addition, improving the mixing degree of graphite sheets and paraffin in bottom scale and reducing the volume fraction of the bottom scale graphite both can improve the effective thermal conductivity coefficient of expanded graphite/paraffin phase change composites effectively. The conclusions obtained lay a foundation for the investigation of the mechanisms of expanded graphite powders improving the thermal conductivity coefficients of phase change composites.
Preparing phase change composites by mixing expanded graphite powders and paraffin can improve the heat transfer performance of the energy storage materials effectively. In order to investigate the thermal conductivity mechanism of expanded graphite/paraffin phase change composites, the calculation method of the effective thermal conductivity coefficients of three scales solid after the mixture of expanded graphite powders and paraffin was put forward. Then, by numerically simulation calculation, the effective thermal conductivity coefficients of expanded graphite/paraffin phase change composites containing expanded graphite thermal conductive particles with different volume fractions and different thermal conductivity coefficients were obtained. The results show that expanded graphite can improve the heat conduction performance of paraffin greatly, and when the volume fraction of expanded graphite is 10%, the effective thermal conductivity coefficient of expanded graphite/paraffin phase change composite is as high as 9 times of the pure paraffin. In addition, improving the mixing degree of graphite sheets and paraffin in bottom scale and reducing the volume fraction of the bottom scale graphite both can improve the effective thermal conductivity coefficient of expanded graphite/paraffin phase change composites effectively. The conclusions obtained lay a foundation for the investigation of the mechanisms of expanded graphite powders improving the thermal conductivity coefficients of phase change composites.
Preparation and properties characterization of nano hydroxyapatite/polyamide 6 biomedical composites
2015, 32(6): 1602-1610.
doi: 10.13801/j.cnki.fhclxb.20150413.001
Abstract:
In order to prevent the conglomerating of nano hydroxyapatite (nano HAP) powders, the nano HAP/polyamide 6 (PA6) composite powders were prepared by solvent precipitation method, and nano HAP/PA6 composites were obtained through hot-press forming of the powders. Then, the constituent, structure and morphology of nano HAP/PA6 composites were investigated using FTIR, XRD and SEM, and thermal stability, mechanical properties and cellular compatibility of composites were measured as well. The results show that the crystalline size of prepared nano HAP/PA6 composites is uniform, and PA6 only has the crystal of α form. For new hydrogen bonds and COO—Ca forming on the interface of nano HAP and PA6, the composites have good synthetic performances. Nano HAP/PA6 composite does not split within 350 ℃, and the mechanical properties are close to human skeleton. The bending strength, compressive strength and elastic modulus of 50wt% nano HAP/PA6 composite are 146.87 MPa, 98.44 MPa and 5.44 GPa, respectively. The situations of MG-63 bone tumor cells attaching and growth on the surfaces of nano HAP/PA6 composites are good, which indicates the nano HAP/PA6 composites have good cellular compatibility. The conclusions obtainted show that nano HAP/PA6 composites have application values in bone repair aspect.
In order to prevent the conglomerating of nano hydroxyapatite (nano HAP) powders, the nano HAP/polyamide 6 (PA6) composite powders were prepared by solvent precipitation method, and nano HAP/PA6 composites were obtained through hot-press forming of the powders. Then, the constituent, structure and morphology of nano HAP/PA6 composites were investigated using FTIR, XRD and SEM, and thermal stability, mechanical properties and cellular compatibility of composites were measured as well. The results show that the crystalline size of prepared nano HAP/PA6 composites is uniform, and PA6 only has the crystal of α form. For new hydrogen bonds and COO—Ca forming on the interface of nano HAP and PA6, the composites have good synthetic performances. Nano HAP/PA6 composite does not split within 350 ℃, and the mechanical properties are close to human skeleton. The bending strength, compressive strength and elastic modulus of 50wt% nano HAP/PA6 composite are 146.87 MPa, 98.44 MPa and 5.44 GPa, respectively. The situations of MG-63 bone tumor cells attaching and growth on the surfaces of nano HAP/PA6 composites are good, which indicates the nano HAP/PA6 composites have good cellular compatibility. The conclusions obtainted show that nano HAP/PA6 composites have application values in bone repair aspect.
2015, 32(6): 1611-1617.
doi: 10.13801/j.cnki.fhclxb.20150325.002
Abstract:
In order to promote the stiffness and thermal dimensional stability of carbon fiber/epoxy composites, carbon fiber network reinforcement (CFNR) was fabricated firstly by short carbon fiber, and mixed with epoxy to prepare new type of CFRN/epoxy composites. Then, the microstructure and thermal mechanical properties of CFRN/epoxy composite were characterized by scanning electron microscopy and thermal mechanical analyzer, respectively. The results indicate that there are obvious network nodes of carbon-based adhesive points in CFNR/epoxy composites, and CFNR/epoxy composites exhibit relatively high electric conductivity, high stiffness and low thermal expansion, the elastic modulus is about 3 times and 6 times of that of regular short carbon fiber/epoxy composite and pure epoxy, respectively. The average thermal expansion coefficient (60-200 ℃) is 1/15 of that of regular short carbon fiber/epoxy composite, and 1/40 of that of pure epoxy, respectively. With the temperature increasing, the elastic moduli of CFNR/epoxy composite, regular short carbon fiber/epoxy composite and pure epoxy are dropping due to the softening of epoxy. When the temperature is above 80 ℃, the elastic modulus of CFNR/epoxy composite is about 7 times of that of regular short carbon fiber/epoxy composite, and nearly 70 times of that of pure epoxy. The research conclusions can provide experimental basis and theoretical direction for the exploring of polymer matrix composites with high stiffness and low thermal expansion.
In order to promote the stiffness and thermal dimensional stability of carbon fiber/epoxy composites, carbon fiber network reinforcement (CFNR) was fabricated firstly by short carbon fiber, and mixed with epoxy to prepare new type of CFRN/epoxy composites. Then, the microstructure and thermal mechanical properties of CFRN/epoxy composite were characterized by scanning electron microscopy and thermal mechanical analyzer, respectively. The results indicate that there are obvious network nodes of carbon-based adhesive points in CFNR/epoxy composites, and CFNR/epoxy composites exhibit relatively high electric conductivity, high stiffness and low thermal expansion, the elastic modulus is about 3 times and 6 times of that of regular short carbon fiber/epoxy composite and pure epoxy, respectively. The average thermal expansion coefficient (60-200 ℃) is 1/15 of that of regular short carbon fiber/epoxy composite, and 1/40 of that of pure epoxy, respectively. With the temperature increasing, the elastic moduli of CFNR/epoxy composite, regular short carbon fiber/epoxy composite and pure epoxy are dropping due to the softening of epoxy. When the temperature is above 80 ℃, the elastic modulus of CFNR/epoxy composite is about 7 times of that of regular short carbon fiber/epoxy composite, and nearly 70 times of that of pure epoxy. The research conclusions can provide experimental basis and theoretical direction for the exploring of polymer matrix composites with high stiffness and low thermal expansion.
2015, 32(6): 1618-1624.
doi: 10.13801/j.cnki.fhclxb.20151113.002
Abstract:
In order to verify the synergistic flame-retardant effects of silicon-containing macromolecular compatibilizer in halogen-free flame-retardant systems, using maleic anhydride, silicone rubber and polyethylene as raw materials, a novel silicon-containing flame-retardant macromolecular compatibilizer was prepared by melting graft copolymerization firstly. Then the polyethylene composites were inflaming retarded synergistically by compounding of aluminium hydroxide, magnesium hydroxide and silicon-containing macromolecular compatibilizer. Finally, the effects of silicon-containing macromolecular compatibilizer on limiting oxygen index, parameters of cone calorimetry, tensile properties and microstructures of the composites were investigated. The results show that compared with polyethylene grafted maleic anhydride, when the silicon-containing macromolecular compatibilizer content is 10wt%, the inorganic flame-retardants are dispersed better in matrix resin. With the macromolecular compatibilizer content increasing, the tensile strength of composite increases but the elongation at break decreases. The limiting oxygen index increases to 34.0%, and the peak value of heat release rate and total heat release of burning decrease siginificantly, which means that the silicon-containing macromolecular compatibilizer can not only play a favorable compatible role in the composites, but also shows a better synergistic flame-retardant effect.
In order to verify the synergistic flame-retardant effects of silicon-containing macromolecular compatibilizer in halogen-free flame-retardant systems, using maleic anhydride, silicone rubber and polyethylene as raw materials, a novel silicon-containing flame-retardant macromolecular compatibilizer was prepared by melting graft copolymerization firstly. Then the polyethylene composites were inflaming retarded synergistically by compounding of aluminium hydroxide, magnesium hydroxide and silicon-containing macromolecular compatibilizer. Finally, the effects of silicon-containing macromolecular compatibilizer on limiting oxygen index, parameters of cone calorimetry, tensile properties and microstructures of the composites were investigated. The results show that compared with polyethylene grafted maleic anhydride, when the silicon-containing macromolecular compatibilizer content is 10wt%, the inorganic flame-retardants are dispersed better in matrix resin. With the macromolecular compatibilizer content increasing, the tensile strength of composite increases but the elongation at break decreases. The limiting oxygen index increases to 34.0%, and the peak value of heat release rate and total heat release of burning decrease siginificantly, which means that the silicon-containing macromolecular compatibilizer can not only play a favorable compatible role in the composites, but also shows a better synergistic flame-retardant effect.
2015, 32(6): 1625-1632.
doi: 10.13801/j.cnki.fhclxb.20150210.001
Abstract:
In order to investigate the flocking performances and sound insulating properties of nylon 66 fibers/aluminium alloy 6061 composite plates under different flocking technology conditions, aluminium alloy 6061 plates and nylon 66 fibers were composited to prepare the sound insulation composite plates by electrostatic flocking technology. Then, the effects of processing parameters such as flocking time, flocking voltage, plate distance and adhesive coating amount et al on flocking areal density and wearability of flocking fibers were investigated. Finally, the sound insulation properties of nylon 66 fibers/aluminium alloy 6061 composite plates under different frequencies of incoming audio and with different structural parameters of fibers were investigated by reverberation-anechoic chamber method. The results show that in the flocking time range of 0-40 s, the flocking areal density increases continuously with the flocking time increasing and then remains unchanged. While in the voltage range of 0-90 kV, with the increasing of voltage, flocking areal density increases continuously and then increases or decreases for the difference of plate distance. Wearability of flocking fibers increases with the increasing of adhesive coating amount, but after the coating amount surpasses 155 g/m2, the gas bubbles generate. When the flocking time is 40 s, flocking voltage is 90 kV, plate distance is 11.5 cm and adhesive coating amount is 155 g/m2, the nylon 66 fibers/aluminium alloy 6061 composite plates have the best properties. The composite plates have preferable sound insulating properties at medium and high frequencies, sound reduction index goes with the rule of 6 dB/octave within the frequency range of 500-1 600 Hz, and the tally effect occurs after 2 000 Hz. The sound reduction index of the nylon 66 fibers/aluminium alloy 6061 composite plates can be enhanced by increasing the flocking areal density and decreasing the nylon 66 fiber diameter. The research conclusions can lay the foundation for the development and application of new sound insulating composites used in architecture.
In order to investigate the flocking performances and sound insulating properties of nylon 66 fibers/aluminium alloy 6061 composite plates under different flocking technology conditions, aluminium alloy 6061 plates and nylon 66 fibers were composited to prepare the sound insulation composite plates by electrostatic flocking technology. Then, the effects of processing parameters such as flocking time, flocking voltage, plate distance and adhesive coating amount et al on flocking areal density and wearability of flocking fibers were investigated. Finally, the sound insulation properties of nylon 66 fibers/aluminium alloy 6061 composite plates under different frequencies of incoming audio and with different structural parameters of fibers were investigated by reverberation-anechoic chamber method. The results show that in the flocking time range of 0-40 s, the flocking areal density increases continuously with the flocking time increasing and then remains unchanged. While in the voltage range of 0-90 kV, with the increasing of voltage, flocking areal density increases continuously and then increases or decreases for the difference of plate distance. Wearability of flocking fibers increases with the increasing of adhesive coating amount, but after the coating amount surpasses 155 g/m2, the gas bubbles generate. When the flocking time is 40 s, flocking voltage is 90 kV, plate distance is 11.5 cm and adhesive coating amount is 155 g/m2, the nylon 66 fibers/aluminium alloy 6061 composite plates have the best properties. The composite plates have preferable sound insulating properties at medium and high frequencies, sound reduction index goes with the rule of 6 dB/octave within the frequency range of 500-1 600 Hz, and the tally effect occurs after 2 000 Hz. The sound reduction index of the nylon 66 fibers/aluminium alloy 6061 composite plates can be enhanced by increasing the flocking areal density and decreasing the nylon 66 fiber diameter. The research conclusions can lay the foundation for the development and application of new sound insulating composites used in architecture.
2015, 32(6): 1633-1640.
doi: 10.13801/j.cnki.fhclxb.20150420.002
Abstract:
U3160 carbon fabric reinforced 3266 epoxy composites toughened by polyamide nonwoven fabric (PNF) (U3160-PNF/3266) were fabricated using PNF as structured toughening layer. Both the in-plane mechanical properties of U3160-PNF/3266 composites and the effect of hygrothermal ageing on mechanical properties were investigated. The interlaminar morphological analysis of the composites was also performed before and after hygrothermal ageing. The results show that the use of PNF as toughening layer does not lead to the decline of in-plane mechanical properties of composites. Meanwhile tensile properties of the toughened U3160-PNF/3266 composites in 90° even slightly increase compared with untoughened U3160 carbon fabric reinforced 3266 epoxy (U3160/3266) composites. While the matrix and interfacial properties of U3160-PNF/3266 composites are noticeable influenced by hygrothermal ageing, especially for the interfacial bonding property between the nylon fiber and the resin matrix. The retention rates of properties of compression in 90° and interlaminar shear of the toughened composites are lower than those of the untoughened composites obviously after hygrothermal ageing.
U3160 carbon fabric reinforced 3266 epoxy composites toughened by polyamide nonwoven fabric (PNF) (U3160-PNF/3266) were fabricated using PNF as structured toughening layer. Both the in-plane mechanical properties of U3160-PNF/3266 composites and the effect of hygrothermal ageing on mechanical properties were investigated. The interlaminar morphological analysis of the composites was also performed before and after hygrothermal ageing. The results show that the use of PNF as toughening layer does not lead to the decline of in-plane mechanical properties of composites. Meanwhile tensile properties of the toughened U3160-PNF/3266 composites in 90° even slightly increase compared with untoughened U3160 carbon fabric reinforced 3266 epoxy (U3160/3266) composites. While the matrix and interfacial properties of U3160-PNF/3266 composites are noticeable influenced by hygrothermal ageing, especially for the interfacial bonding property between the nylon fiber and the resin matrix. The retention rates of properties of compression in 90° and interlaminar shear of the toughened composites are lower than those of the untoughened composites obviously after hygrothermal ageing.
2015, 32(6): 1641-1648.
doi: 10.13801/j.cnki.fhclxb.20150310.001
Abstract:
To analyze the interfacial compatibility mechanism in wood flour/polymer composites, the temperature spectra and frequency spectra of polar wood flour/polypropylene composites with different loading levels of silane coupling agent were researched through dielectric relaxation process and then the apparent activation energy and thermodynamic quantity in dielectric relaxation process were calculated. The results show that there is relaxation process in poplar wood flour/polypropylene composites with silane coupling agent which is based on reorientation of the methynol groups in amorphous region of wood cell wall. The dielectric relaxation strength decreases first then slowly increases with silane coupling agent loading. The distribution peaks of relaxation time are high and narrow at the beginning then are broader and lower, finally narrower and higher again with increasing silane coupling agent. The values of apparent activation energy, activation enthalpy, activation free energy and activation entropy tend to increase first and then decrease with increasing silane coupling agent. Apparent activation energy and activation enthalpy of 2.0% silane coupling agent modified composites show the maximal value among all the tested conditions, which is 28.12 kJ/mol and 26.35 kJ/mol,respectively, more than twice and 117.9% as likely to samples without coupling agent. It suggestes that the reorientation of the methylol groups becomes very difficult under the strong hindrance. The compatibility between poplar wood flour and polypropylene plastic is better, and the internal bonding and interface strength is stronger, property is more stable.
To analyze the interfacial compatibility mechanism in wood flour/polymer composites, the temperature spectra and frequency spectra of polar wood flour/polypropylene composites with different loading levels of silane coupling agent were researched through dielectric relaxation process and then the apparent activation energy and thermodynamic quantity in dielectric relaxation process were calculated. The results show that there is relaxation process in poplar wood flour/polypropylene composites with silane coupling agent which is based on reorientation of the methynol groups in amorphous region of wood cell wall. The dielectric relaxation strength decreases first then slowly increases with silane coupling agent loading. The distribution peaks of relaxation time are high and narrow at the beginning then are broader and lower, finally narrower and higher again with increasing silane coupling agent. The values of apparent activation energy, activation enthalpy, activation free energy and activation entropy tend to increase first and then decrease with increasing silane coupling agent. Apparent activation energy and activation enthalpy of 2.0% silane coupling agent modified composites show the maximal value among all the tested conditions, which is 28.12 kJ/mol and 26.35 kJ/mol,respectively, more than twice and 117.9% as likely to samples without coupling agent. It suggestes that the reorientation of the methylol groups becomes very difficult under the strong hindrance. The compatibility between poplar wood flour and polypropylene plastic is better, and the internal bonding and interface strength is stronger, property is more stable.
2015, 32(6): 1649-1657.
doi: 10.13801/j.cnki.fhclxb.20150302.002
Abstract:
Novel liquid composites of polyester/cellulose evenly dispersed in aqueous phase were prepared by blending polyethylene glycol (PEG) modified poly(butylene succinate) (PEG/PBS) and modified cellulose carboxymethylcellulose (CMC) and hydroxyethyl cellulose (HEC) respectively. The interaction mechanism of liquid composites was investigated by molecular simulation technology. The results show that the desired structure of PEG/PBS copolymer is successfully achieved by 1H-NMR. Molecular dynamics simulation displays that the polarity and flexibility of copolymer chain have been effectively improved by the modification on double helix structure of PBS with PEG. The introduction of PEG changes the structure regularity. As a consequence, the compatibility between it and cellulose derivatives is improved. The analysis on energy distribution of composites indicates that strong hydrogen bonding and Van der Waals interaction exist between ether and ester group of PEG/PBS and hydroxyl groups of cellulose derivatives. These results have been explained by the deviation of absorption peak frequency on functional groups (such as OH, -OCO-, -COOH and -C-O-C-) in FTIR spectra, the change of surface interfacial morphologies in SEM photographs and the content change of C and O elements in EDS spectrum. The results show that the interaction is produced between functional groups of PBS, etherification PEG/PBS and CMC. And the interaction is improved after etherification modification. The transmittance of composites increases from 50% to more than 70%, the thermal stabilities and flexibility are also enhanced which verifies the results of molecular simulation.
Novel liquid composites of polyester/cellulose evenly dispersed in aqueous phase were prepared by blending polyethylene glycol (PEG) modified poly(butylene succinate) (PEG/PBS) and modified cellulose carboxymethylcellulose (CMC) and hydroxyethyl cellulose (HEC) respectively. The interaction mechanism of liquid composites was investigated by molecular simulation technology. The results show that the desired structure of PEG/PBS copolymer is successfully achieved by 1H-NMR. Molecular dynamics simulation displays that the polarity and flexibility of copolymer chain have been effectively improved by the modification on double helix structure of PBS with PEG. The introduction of PEG changes the structure regularity. As a consequence, the compatibility between it and cellulose derivatives is improved. The analysis on energy distribution of composites indicates that strong hydrogen bonding and Van der Waals interaction exist between ether and ester group of PEG/PBS and hydroxyl groups of cellulose derivatives. These results have been explained by the deviation of absorption peak frequency on functional groups (such as OH, -OCO-, -COOH and -C-O-C-) in FTIR spectra, the change of surface interfacial morphologies in SEM photographs and the content change of C and O elements in EDS spectrum. The results show that the interaction is produced between functional groups of PBS, etherification PEG/PBS and CMC. And the interaction is improved after etherification modification. The transmittance of composites increases from 50% to more than 70%, the thermal stabilities and flexibility are also enhanced which verifies the results of molecular simulation.
2015, 32(6): 1658-1662.
doi: 10.13801/j.cnki.fhclxb.20150323.001
Abstract:
The electric-arc-produced graphene materials were characterized and evaluated by a series of methods such as X-ray photoelectron spectroscopy, Raman spectra, infrared spectroscopy and scanning electron microscope analysis. Results show that the content of C element in graphene is 89.77%, and those of O and N elements are 3.03% and 7.21%. The sample has been identified as multilayer graphene-based Raman spectra G peak and 2D peak position. Adsorption of water in graphene sample is also detected by infrared spectroscopy. The layer number and size of graphene layer structure are observed through microscopic observation. This paper summarized a series of test schemes to characterize graphene,which provides a basis of evaluation for the dissemination and application of graphene in composites.
The electric-arc-produced graphene materials were characterized and evaluated by a series of methods such as X-ray photoelectron spectroscopy, Raman spectra, infrared spectroscopy and scanning electron microscope analysis. Results show that the content of C element in graphene is 89.77%, and those of O and N elements are 3.03% and 7.21%. The sample has been identified as multilayer graphene-based Raman spectra G peak and 2D peak position. Adsorption of water in graphene sample is also detected by infrared spectroscopy. The layer number and size of graphene layer structure are observed through microscopic observation. This paper summarized a series of test schemes to characterize graphene,which provides a basis of evaluation for the dissemination and application of graphene in composites.
2015, 32(6): 1663-1672.
doi: 10.13801/j.cnki.fhclxb.20150316.001
Abstract:
The light stabilizer/di-methyl silicon oil blend composites were prepared by adding hydroxy-4-methoxy-benzophenone (UV-9) and a hindered amine light stabilizer named GW-783 into di-methyl silicon oil and the composites applied as heat transfer medium for concentrator solar cells were studied. By accelerated life test, the weather resistance of the composites, viscosity and spectral transmittance were investigated and the mass fraction range of light stabilizer in composites during working process were defined. And the performance of concentrator soalr cells before and after test was also detected and analyzed. The results show that the aging effect on light stabilizer/di-methyl silicon oil blend composites can be inhibited efficiently and there are no interaction between concentrator solar cells and composites. Hence, the power performance of concentrator solar cells can be kept stable when concentrating photovoltaic (CPV) system is running for a long time. The most effect composite is UV-9-GW-783/di-methyl silicon oil.
The light stabilizer/di-methyl silicon oil blend composites were prepared by adding hydroxy-4-methoxy-benzophenone (UV-9) and a hindered amine light stabilizer named GW-783 into di-methyl silicon oil and the composites applied as heat transfer medium for concentrator solar cells were studied. By accelerated life test, the weather resistance of the composites, viscosity and spectral transmittance were investigated and the mass fraction range of light stabilizer in composites during working process were defined. And the performance of concentrator soalr cells before and after test was also detected and analyzed. The results show that the aging effect on light stabilizer/di-methyl silicon oil blend composites can be inhibited efficiently and there are no interaction between concentrator solar cells and composites. Hence, the power performance of concentrator solar cells can be kept stable when concentrating photovoltaic (CPV) system is running for a long time. The most effect composite is UV-9-GW-783/di-methyl silicon oil.
2015, 32(6): 1673-1680.
doi: 10.13801/j.cnki.fhclxb.20150331.001
Abstract:
Carbon fiber(T700)/bismaleimide (HT280) composites were performed by air thermal cycles experiments from -60 ℃ to 180 ℃. The low-velocity impact property and mass loss rate of materials were tested before and after air thermal cycles, respectively. Internal damage condition of materials after impact was analyzed using ultrasonic C-scanning. The experimental results show that the mass loss rate rises rapidly and then levels off with increasing air thermal cycles. The average damage area size of sample before and after air thermal cycles increases and the fracture mode varies with the increase of low-velocity impact energy. The average damage area size and absorbed energy of sample after air thermal cycles are bigger than the ones of sample in original state when subjected to the same low-velocity impact energy.
Carbon fiber(T700)/bismaleimide (HT280) composites were performed by air thermal cycles experiments from -60 ℃ to 180 ℃. The low-velocity impact property and mass loss rate of materials were tested before and after air thermal cycles, respectively. Internal damage condition of materials after impact was analyzed using ultrasonic C-scanning. The experimental results show that the mass loss rate rises rapidly and then levels off with increasing air thermal cycles. The average damage area size of sample before and after air thermal cycles increases and the fracture mode varies with the increase of low-velocity impact energy. The average damage area size and absorbed energy of sample after air thermal cycles are bigger than the ones of sample in original state when subjected to the same low-velocity impact energy.
2015, 32(6): 1681-1687.
doi: 10.13801/j.cnki.fhclxb.20150505.002
Abstract:
To evaluate the properties of mesoporous nano hydroxyapatite (MHA)/poly(L-lactide) (PLLA) composites, MHA was synthesized with cetyltrimethylammonium bromide (CTAB) as template. MHA/PLLA porous scaffold composites with different contents of nano particles were prepared using solution phase separation and particle-leaching method, and the compressive property and micro-structure of quenching fracture cross-sections were evaluated. And then MHA/PLLA composite films were prepared using solvent casting method and the tensile property and micro-structure of tensile fracture cross-sections were evaluated. FTIR, XRD, TEM and N2 adsorption test results show that the prepared MHA has typical crystal structure, mesoporous structure and higher specific surface area. The mechanical test show that the MHA/PLLA porous scaffold composites with filler content of 1%, 5% and 10% exhibit increasing compressive strength under 10% compression deformation with the filler content increasing, and are 37.0%、67.7% and 144.7% higher than those of corresponding content of nano hydroxyapatite (HA)/PLLA porous scaffold composites, respectively. With the filler content of 5% and 10%, the tensile strength of MHA/PLLA composite films are 38.7% and 46.1% higher than those of HA/PLLA composite films, the strength modulus are 35.4% and 14.5% higher, respectively. And MHA/PLLA composite films possess higher elongation at break. With the filler content of 1%, 5% and 10%, the elongation at break are 91.3%, 79.7% and 96.1% higher than those of HA/PLLA composite films, respectively. FESEM photographs show that the distribution of filler particles in MHA/PLLA porous scaffold composites or composite films is more uniform than that in HA/PLLA when the filler content is higher. The results indicate that, compared with HA/PLLA composites, better mechanical property and more evenly MHA distribution in PLLA matrix are obtained as the increasing content of MHA.
To evaluate the properties of mesoporous nano hydroxyapatite (MHA)/poly(L-lactide) (PLLA) composites, MHA was synthesized with cetyltrimethylammonium bromide (CTAB) as template. MHA/PLLA porous scaffold composites with different contents of nano particles were prepared using solution phase separation and particle-leaching method, and the compressive property and micro-structure of quenching fracture cross-sections were evaluated. And then MHA/PLLA composite films were prepared using solvent casting method and the tensile property and micro-structure of tensile fracture cross-sections were evaluated. FTIR, XRD, TEM and N2 adsorption test results show that the prepared MHA has typical crystal structure, mesoporous structure and higher specific surface area. The mechanical test show that the MHA/PLLA porous scaffold composites with filler content of 1%, 5% and 10% exhibit increasing compressive strength under 10% compression deformation with the filler content increasing, and are 37.0%、67.7% and 144.7% higher than those of corresponding content of nano hydroxyapatite (HA)/PLLA porous scaffold composites, respectively. With the filler content of 5% and 10%, the tensile strength of MHA/PLLA composite films are 38.7% and 46.1% higher than those of HA/PLLA composite films, the strength modulus are 35.4% and 14.5% higher, respectively. And MHA/PLLA composite films possess higher elongation at break. With the filler content of 1%, 5% and 10%, the elongation at break are 91.3%, 79.7% and 96.1% higher than those of HA/PLLA composite films, respectively. FESEM photographs show that the distribution of filler particles in MHA/PLLA porous scaffold composites or composite films is more uniform than that in HA/PLLA when the filler content is higher. The results indicate that, compared with HA/PLLA composites, better mechanical property and more evenly MHA distribution in PLLA matrix are obtained as the increasing content of MHA.
2015, 32(6): 1688-1695.
doi: 10.13801/j.cnki.fhclxb.20150327.003
Abstract:
The glass fiber-hollow glass microsphere/epoxy syntactic foam material with different fiber mass fractions were prepared. The effects of fiber mass fraction on mechanical properties of composite foam material were studied by three point bending test. Composite foam material specimens were put in distilled water and seawater. The influences of soak corrosion on flexural properties of specimens were studied, and the reasons were analyzed by combining with the scanning electron microscopy photos. The research reveals that the moisture rate of glass fiber-hollow glass microsphere/epoxy composites increases with the increase of fiber mass fraction, and the moisture rate of specimen in distilled water is greater than that of specimen in seawater. The flexural strength of specimens increases with the increasing fiber mass fraction, and it goes to be maximum when the fiber mass fraction is 10%, more than that of specimen without fiber by 51%, then it decreases with further adding fibers. The flexural properties of specimens are reduced by soak corrosion, and it is lower in seawater than that in distilled water. The interface layers between glass microsphere, glass fiber and epoxy matrix are damaged by soak corrosion, and it is the reason of the decrease of flexural strength of glass fiber-hollow glass microsphere/epoxy composites.
The glass fiber-hollow glass microsphere/epoxy syntactic foam material with different fiber mass fractions were prepared. The effects of fiber mass fraction on mechanical properties of composite foam material were studied by three point bending test. Composite foam material specimens were put in distilled water and seawater. The influences of soak corrosion on flexural properties of specimens were studied, and the reasons were analyzed by combining with the scanning electron microscopy photos. The research reveals that the moisture rate of glass fiber-hollow glass microsphere/epoxy composites increases with the increase of fiber mass fraction, and the moisture rate of specimen in distilled water is greater than that of specimen in seawater. The flexural strength of specimens increases with the increasing fiber mass fraction, and it goes to be maximum when the fiber mass fraction is 10%, more than that of specimen without fiber by 51%, then it decreases with further adding fibers. The flexural properties of specimens are reduced by soak corrosion, and it is lower in seawater than that in distilled water. The interface layers between glass microsphere, glass fiber and epoxy matrix are damaged by soak corrosion, and it is the reason of the decrease of flexural strength of glass fiber-hollow glass microsphere/epoxy composites.
2015, 32(6): 1696-1702.
doi: 10.13801/j.cnki.fhclxb.20150323.003
Abstract:
In order to investigate the influence of fiber chemical composition on interfacial properties of the reinforced composites, the back propagation (BP) neural network training sample was constructed with the composition cellulose, hemicellulose, pectin, lignin, water-soluble material, grease waxand moisture regain of bast fibers as factors, and the interfacial properties of bast fibers/unsaturated polyester resin (UP) composites as the results. The gray relational analysis method was employed to investigate the correlation degree of factors which have influence on the interfacial properties of bast fibers/UP composites, and the factors were ranked according to the size of influence degree.A three layer BP neural network model was constructed for iterative training. The effects of chemical composition content on interfacial properties of bast fibers/UP composites can be predicted. The prediction results show that the prediction model output is close to the measured values after learning. It proves that the BP neural network has strong ability to learn which means that the BP neural network can be used in the prediction of interfacial shear force of bast fibers/UP composites. The prediction accuracy is greatly improved and can be reduced by as large as 83.28% with the combination of gray relational analysis and BP neural network.
In order to investigate the influence of fiber chemical composition on interfacial properties of the reinforced composites, the back propagation (BP) neural network training sample was constructed with the composition cellulose, hemicellulose, pectin, lignin, water-soluble material, grease waxand moisture regain of bast fibers as factors, and the interfacial properties of bast fibers/unsaturated polyester resin (UP) composites as the results. The gray relational analysis method was employed to investigate the correlation degree of factors which have influence on the interfacial properties of bast fibers/UP composites, and the factors were ranked according to the size of influence degree.A three layer BP neural network model was constructed for iterative training. The effects of chemical composition content on interfacial properties of bast fibers/UP composites can be predicted. The prediction results show that the prediction model output is close to the measured values after learning. It proves that the BP neural network has strong ability to learn which means that the BP neural network can be used in the prediction of interfacial shear force of bast fibers/UP composites. The prediction accuracy is greatly improved and can be reduced by as large as 83.28% with the combination of gray relational analysis and BP neural network.
2015, 32(6): 1703-1713.
doi: 10.13801/j.cnki.fhclxb.20150316.003
Abstract:
The needle rod-like cellulose whiskers (NCW) with nano size and certain length-diameter ratiowere prepared by acid hydrolysis, and then were surface modified with poly (L-lactic acid) (PLLA) segments through thering-opening polymerization of L-lactide initiated by surfacehydroxyl groups to obtain grafted cellulose whiskers(g-NCW). PLLA membrane and NCW/PLLA and g-NCW/PLLA composite membranes with different ratios were prepared by solution casting method. Morphologies and properties of the modified and unmodified NCW were observed, and the morphologies, crystallization properties, thermostability, hydrophilicity/hydrophobicity and tensile properties of the composite membranes were studied too. The results show that the morphology and crystallization property of NCW change little after graft modification, but the dispersion of g-NCW in ethanol and PLLA solution is improved significantly. The grafting percentage of PLLA segments on surface of g-NCW is 23.61% as the ratio of amount of substance of NCW to L-lactide is 1∶5. The crystallization rateof PLLA matrix increases significantly due to the heterogeneous nucleating effect of the NCW and g-NCW. In addition, the hydrophilicity and thermostability of material are improved by the introduction of the whiskers.When adding some content of NCW and g-NCWto PLLA, the strength and toughness of the PLLA matrix are evidently improved. With the content of whiskers increasing, the tensile strength and breaking energy increase first and then decrease for NCW/PLLA and g-NCW/PLLA composite membranes, as the mass fraction of NCW and g-NCW is 5%, the highest tensile strength and breaking energy of 22.02 MPa and 20.01 MPa, 102.39 J/m3 and 117.83 J/m3 are obtained for NCW/PLLA and g-NCW/PLLAcomposite membranes respectively. Due to the excellent dispersionof g-NCW in matrix and interfacial adhesion, the tensile strength and toughness of g-NCW/PLLA composite membranes are obviously superior to those of the pure PLLA and NCW/PLLA membranes.
The needle rod-like cellulose whiskers (NCW) with nano size and certain length-diameter ratiowere prepared by acid hydrolysis, and then were surface modified with poly (L-lactic acid) (PLLA) segments through thering-opening polymerization of L-lactide initiated by surfacehydroxyl groups to obtain grafted cellulose whiskers(g-NCW). PLLA membrane and NCW/PLLA and g-NCW/PLLA composite membranes with different ratios were prepared by solution casting method. Morphologies and properties of the modified and unmodified NCW were observed, and the morphologies, crystallization properties, thermostability, hydrophilicity/hydrophobicity and tensile properties of the composite membranes were studied too. The results show that the morphology and crystallization property of NCW change little after graft modification, but the dispersion of g-NCW in ethanol and PLLA solution is improved significantly. The grafting percentage of PLLA segments on surface of g-NCW is 23.61% as the ratio of amount of substance of NCW to L-lactide is 1∶5. The crystallization rateof PLLA matrix increases significantly due to the heterogeneous nucleating effect of the NCW and g-NCW. In addition, the hydrophilicity and thermostability of material are improved by the introduction of the whiskers.When adding some content of NCW and g-NCWto PLLA, the strength and toughness of the PLLA matrix are evidently improved. With the content of whiskers increasing, the tensile strength and breaking energy increase first and then decrease for NCW/PLLA and g-NCW/PLLA composite membranes, as the mass fraction of NCW and g-NCW is 5%, the highest tensile strength and breaking energy of 22.02 MPa and 20.01 MPa, 102.39 J/m3 and 117.83 J/m3 are obtained for NCW/PLLA and g-NCW/PLLAcomposite membranes respectively. Due to the excellent dispersionof g-NCW in matrix and interfacial adhesion, the tensile strength and toughness of g-NCW/PLLA composite membranes are obviously superior to those of the pure PLLA and NCW/PLLA membranes.
2015, 32(6): 1714-1720.
doi: 10.13801/j.cnki.fhclxb.20150428.004
Abstract:
Ammonium polyphosphate (APP) was used as flame retardant to modify benzoxazine (BOZ) resin and glass fiber (GF) /BOZ composites. The flame retardant mechanism of material was investigated by thermal analysis and microstructure analysis. The results show that APP can significantly improve the flame retardancy of BOZ resin. With the increase of APP content, the limiting oxygen index of resin system increase gradually. The limiting oxygen index of 3wt% APP-BOZ resin increases from 31.5% of matrix to 34.5% and the UL 94 of V-0 is obtained. The APP-BOZ modified resins decompose earlier than BOZ resin, and the glass transition temperatures reduce a little. The curing reactions of modified resin system start at lower temperatures and operate more mildly. With the incorporation of APP, the flame retardancy of GF/BOZ composites gets further improved, and the limiting oxygen index of 10wt% GF/APP-BOZ composites increases from 51.0% of GF/BOZ to 57.7%. Microstructure analysis shows that APP can help to form denser char of APP-BOZ modified resins and GF/APP-BOZ composites to improve the flame retardancy.
Ammonium polyphosphate (APP) was used as flame retardant to modify benzoxazine (BOZ) resin and glass fiber (GF) /BOZ composites. The flame retardant mechanism of material was investigated by thermal analysis and microstructure analysis. The results show that APP can significantly improve the flame retardancy of BOZ resin. With the increase of APP content, the limiting oxygen index of resin system increase gradually. The limiting oxygen index of 3wt% APP-BOZ resin increases from 31.5% of matrix to 34.5% and the UL 94 of V-0 is obtained. The APP-BOZ modified resins decompose earlier than BOZ resin, and the glass transition temperatures reduce a little. The curing reactions of modified resin system start at lower temperatures and operate more mildly. With the incorporation of APP, the flame retardancy of GF/BOZ composites gets further improved, and the limiting oxygen index of 10wt% GF/APP-BOZ composites increases from 51.0% of GF/BOZ to 57.7%. Microstructure analysis shows that APP can help to form denser char of APP-BOZ modified resins and GF/APP-BOZ composites to improve the flame retardancy.
2015, 32(6): 1721-1728.
doi: 10.13801/j.cnki.fhclxb.20150410.001
Abstract:
Carbon nanotubes (CNTs) were prepared directly on carbon fibers by chemical vapor deposition (CVD) method. The different process parameters such as catalyst, deposition temperature, hydrogen flow rate and distance between samples and intake were investigated in relation to morphology and structure. The samples were characterized and analyzed by SEM and high resolution transmission electron microscopy (HRTEM). Results show that CNTs in-situ grown on surface of CF is multi-wall structure. CNTs which grow on carbon fibers surface using Ni-catalyst are thin and uniform distribution. The diameter and length of CNTs using Fe-catalyst reduce and yield decrease when the deposition temperature rises from 600 ℃ to 750 ℃. The diameter and length of CNTs raise with hydrogen flow rate increasing. It is in favor of preparing high quality CNTs at 30 cm from fibers to intake, at which CNTs densely distribute on the carbon fiber surface and their diameter are uniform.
Carbon nanotubes (CNTs) were prepared directly on carbon fibers by chemical vapor deposition (CVD) method. The different process parameters such as catalyst, deposition temperature, hydrogen flow rate and distance between samples and intake were investigated in relation to morphology and structure. The samples were characterized and analyzed by SEM and high resolution transmission electron microscopy (HRTEM). Results show that CNTs in-situ grown on surface of CF is multi-wall structure. CNTs which grow on carbon fibers surface using Ni-catalyst are thin and uniform distribution. The diameter and length of CNTs using Fe-catalyst reduce and yield decrease when the deposition temperature rises from 600 ℃ to 750 ℃. The diameter and length of CNTs raise with hydrogen flow rate increasing. It is in favor of preparing high quality CNTs at 30 cm from fibers to intake, at which CNTs densely distribute on the carbon fiber surface and their diameter are uniform.
2015, 32(6): 1729-1736.
doi: 10.13801/j.cnki.fhclxb.20150211.001
Abstract:
TiB whiskers reinforced Ti60 alloy matrix (TiBW/Ti60) composites with the reinforcement distributing as network microstructure were successfully fabricated by using large spherical Ti60 alloy powders and fine TiB2 powders and processes of low energy milling and reactive hot pressingsintering. Heat treatment was performed on TiBW/Ti60 composites to improve their microstructure and mechanical properties. The results show that the fraction of the primary α phase (hexagonal closepacked phase)in TiBW/Ti60 matrix decreases while that of the transformed β microstructure including α' (martensite) and residual β phase (body-centered cubic phase) increases with increasing solid solution temperatures. Therefore, the tensile strength of TiBW/Ti60 composites increases while the ductility decreases with increasing solid solution temperatures. After solid solution by 1 100 ℃/1 h, the tensile strength of TiBW/Ti60 composites is 1 470 MPa at room temperature along with an elongation of 1.9%. The α' phase in the transformed β microstructure translates into fine α+β phases after aging process. After solid solution by 1 100 ℃/1 h followed by aging at 600 ℃ for 8 h,the hardness of TiBW/Ti60 composites reaches to HV538 and the tensile strength increases to 1 552 MPa along with an elongation of 1.5%.After solid solution by 1 000 ℃/1 h followed by aging at 600 ℃ for 8 h,the tensile strength increases to 1 460 MPa along with an elongation of 2.2%.
TiB whiskers reinforced Ti60 alloy matrix (TiBW/Ti60) composites with the reinforcement distributing as network microstructure were successfully fabricated by using large spherical Ti60 alloy powders and fine TiB2 powders and processes of low energy milling and reactive hot pressingsintering. Heat treatment was performed on TiBW/Ti60 composites to improve their microstructure and mechanical properties. The results show that the fraction of the primary α phase (hexagonal closepacked phase)in TiBW/Ti60 matrix decreases while that of the transformed β microstructure including α' (martensite) and residual β phase (body-centered cubic phase) increases with increasing solid solution temperatures. Therefore, the tensile strength of TiBW/Ti60 composites increases while the ductility decreases with increasing solid solution temperatures. After solid solution by 1 100 ℃/1 h, the tensile strength of TiBW/Ti60 composites is 1 470 MPa at room temperature along with an elongation of 1.9%. The α' phase in the transformed β microstructure translates into fine α+β phases after aging process. After solid solution by 1 100 ℃/1 h followed by aging at 600 ℃ for 8 h,the hardness of TiBW/Ti60 composites reaches to HV538 and the tensile strength increases to 1 552 MPa along with an elongation of 1.5%.After solid solution by 1 000 ℃/1 h followed by aging at 600 ℃ for 8 h,the tensile strength increases to 1 460 MPa along with an elongation of 2.2%.
2015, 32(6): 1737-1744.
doi: 10.13801/j.cnki.fhclxb.20150625.001
Abstract:
A gradient based optimization method for variable stiffness design of laminates was proposed. The optimal element density and orientations were determined in the optimization process. In order to attain industrial relevance, the manufacturing constraint should be satisfied and candidate orientations were limited to a finite set. For the purpose of eliminating the number of constraints and design variables in optimization model, the density distribution curve method (DDCM) was established to parameterize element density. The elastic matrix of element was determined on basis of interpolation scheme in bi-value coding parameterization(BCP) method, according to element density and design variables of orientations. Strucrure compliance and volume were treated as optimization objective and constraint respectively in optimization process. The optimization problem was solved by the convex programming dual algorithm. Numerical examples for the carbon fiber composite demonstrate that reasonable results can be got by DDCM with relatively high convergence rate.
A gradient based optimization method for variable stiffness design of laminates was proposed. The optimal element density and orientations were determined in the optimization process. In order to attain industrial relevance, the manufacturing constraint should be satisfied and candidate orientations were limited to a finite set. For the purpose of eliminating the number of constraints and design variables in optimization model, the density distribution curve method (DDCM) was established to parameterize element density. The elastic matrix of element was determined on basis of interpolation scheme in bi-value coding parameterization(BCP) method, according to element density and design variables of orientations. Strucrure compliance and volume were treated as optimization objective and constraint respectively in optimization process. The optimization problem was solved by the convex programming dual algorithm. Numerical examples for the carbon fiber composite demonstrate that reasonable results can be got by DDCM with relatively high convergence rate.
2015, 32(6): 1745-1753.
doi: 10.13801/j.cnki.fhclxb.20150505.001
Abstract:
In order to overcome the disadvantage of traditional cohesive zone damage model (CZM) that it cannot present the effect of intralaminar cracks on delamination interface, a modified CZM has been developed for simulation of damage process of composite laminates subject to low-velocity impact. By means of the modification of the damage initiation criteria of cohesion constitutive model used in interface element, the influences of damage status and stress distribution of matrix and fiber in neighboring interface layers on interlaminar strength and delamination propagation have been taken into account. The proposed model, combined with intralaminar failure criterion, was implemented to ABAQUS as a user defined subroutine VUMAT to simulate the progressive damage process of composite laminate under low-velocity impact. In order to valid the accuracy and rationality of this method, the damage status of composite laminates with different ply orientations and material properties are compared with test results.
In order to overcome the disadvantage of traditional cohesive zone damage model (CZM) that it cannot present the effect of intralaminar cracks on delamination interface, a modified CZM has been developed for simulation of damage process of composite laminates subject to low-velocity impact. By means of the modification of the damage initiation criteria of cohesion constitutive model used in interface element, the influences of damage status and stress distribution of matrix and fiber in neighboring interface layers on interlaminar strength and delamination propagation have been taken into account. The proposed model, combined with intralaminar failure criterion, was implemented to ABAQUS as a user defined subroutine VUMAT to simulate the progressive damage process of composite laminate under low-velocity impact. In order to valid the accuracy and rationality of this method, the damage status of composite laminates with different ply orientations and material properties are compared with test results.
2015, 32(6): 1754-1761.
doi: 10.13801/j.cnki.fhclxb.20150410.006
Abstract:
To study the impact and fatigue properties of composite stiffened panels, which are widely used in aircraft vertical tail, the multi-impact, high cycle fatigue and residual compressive strength tests were designed based on the composite stiffened panels. The effects of different impact energy on impact damage of stiffener edge were discussed, and damage area development condition under fatigue load of low stress level was also studied. The effect of fatigue on residual compressive strength after impact was given. Results show that the damage areas and dent depth of 40 J impact energy are large, and the damage morphologies of C-scan test are more irregular. The new damage is promoted from main damage area after one million low stress fatigue, and the crack induced by compression failure is propagated to the top and bottom fixed jig. The stiffened panels exhibit better impact and fatigue damage resistance since the retention rate of breaking load after fatigue is about 95.6%. The results can be used for durability and postbuckling design of stiffened panels.
To study the impact and fatigue properties of composite stiffened panels, which are widely used in aircraft vertical tail, the multi-impact, high cycle fatigue and residual compressive strength tests were designed based on the composite stiffened panels. The effects of different impact energy on impact damage of stiffener edge were discussed, and damage area development condition under fatigue load of low stress level was also studied. The effect of fatigue on residual compressive strength after impact was given. Results show that the damage areas and dent depth of 40 J impact energy are large, and the damage morphologies of C-scan test are more irregular. The new damage is promoted from main damage area after one million low stress fatigue, and the crack induced by compression failure is propagated to the top and bottom fixed jig. The stiffened panels exhibit better impact and fatigue damage resistance since the retention rate of breaking load after fatigue is about 95.6%. The results can be used for durability and postbuckling design of stiffened panels.
2015, 32(6): 1762-1768.
doi: 10.13801/j.cnki.fhclxb.20151113.003
Abstract:
In order to study damage initiation, evolution ways and damage characteristic of carbon fiber reinforced resin matrix composites open-hole laminates under compression load, compressive tests of open-hole domestic CCF300/5228A laminates of three kinds of layup [45/0/-45/90]4s, [452/02/-452/902]2s, [454/04/-454/904]s were investigated based on four methods: macro photography, ultrasonic C-scan together with multi-stage loading, X-scan and scanning electron microscope. The damage initiation and damage propagation of open-hole laminates under compression load were observed and compared. The fiber micro-buckling, fiber extrusion, cracks and delamination on hole edge during tests were analyzed and explained. The test results show that delamination occurs easily at positions between 45° and 90° layups of laminates under compression load. Phenomenon of progressive damage is obvious at the edge of the hole in laminates within positions between 45° and 90° layups. The relief of stress concentration and strain energy on the hole edge are caused by the early initiation and propagation of damage. The relief delays the final failure and increases compressive bearing capacity of the laminates. The results can provide a guidance for the damage tolerance design of composite structures.
In order to study damage initiation, evolution ways and damage characteristic of carbon fiber reinforced resin matrix composites open-hole laminates under compression load, compressive tests of open-hole domestic CCF300/5228A laminates of three kinds of layup [45/0/-45/90]4s, [452/02/-452/902]2s, [454/04/-454/904]s were investigated based on four methods: macro photography, ultrasonic C-scan together with multi-stage loading, X-scan and scanning electron microscope. The damage initiation and damage propagation of open-hole laminates under compression load were observed and compared. The fiber micro-buckling, fiber extrusion, cracks and delamination on hole edge during tests were analyzed and explained. The test results show that delamination occurs easily at positions between 45° and 90° layups of laminates under compression load. Phenomenon of progressive damage is obvious at the edge of the hole in laminates within positions between 45° and 90° layups. The relief of stress concentration and strain energy on the hole edge are caused by the early initiation and propagation of damage. The relief delays the final failure and increases compressive bearing capacity of the laminates. The results can provide a guidance for the damage tolerance design of composite structures.
2015, 32(6): 1769-1776.
doi: 10.13801/j.cnki.fhclxb.20150424.001
Abstract:
Based on Voxel finite element mesh, the stress analysis of spherical inclusion composites was conducted. The obvious stress concentration phenomenon of elements neighboring interface was induced by the stepped interface within Voxel mesh. A local stress averaging method was proposed to treat the stress concentration induced by Voxel finite element mesh. In addition, the effects of stress averaging domain, stress averaging weight function and mesh density were taken into account. It is found that the local stress averaging method can effectively reduce the stress concentration of elements neighboring interface. But the averaging domain size should be not too big or too small. The two depth layer Voxel elements are the best choice as the averaging domain through calculation, which also has mesh independence. The method can be further used in the progressive damage evolution analysis of the spherical inclusion composites.
Based on Voxel finite element mesh, the stress analysis of spherical inclusion composites was conducted. The obvious stress concentration phenomenon of elements neighboring interface was induced by the stepped interface within Voxel mesh. A local stress averaging method was proposed to treat the stress concentration induced by Voxel finite element mesh. In addition, the effects of stress averaging domain, stress averaging weight function and mesh density were taken into account. It is found that the local stress averaging method can effectively reduce the stress concentration of elements neighboring interface. But the averaging domain size should be not too big or too small. The two depth layer Voxel elements are the best choice as the averaging domain through calculation, which also has mesh independence. The method can be further used in the progressive damage evolution analysis of the spherical inclusion composites.
2015, 32(6): 1777-1783.
doi: 10.13801/j.cnki.fhclxb.20150323.002
Abstract:
In order to investigate the friction and wear properties of ZrO2 reinforced hydroxyapatite (HA) composite coatings in bovine serum lubrication environment, HA bio-ceramic coatings whose ZrO2 contents were 0, 15wt% and 30wt% respectively were prepared on titanium alloy substrates by plasma spraying technology firstly. Then, the phase formation and bonding strength of ZrO2/HA composite coatings were analyzed. Finally, the friction and wear properties of ZrO2/HA composite coatings in bovine serum lubrication environment were investigated with UMT-3 pin-disk wear tester, the morphologies of wear surfaces of coatings were observed and the wear mechanisms were analyzed. The results show that the main phase of HA coatings are HA, the ZrO2 in 15wt% ZrO2/HA composite coating and 30wt% ZrO2/HA composite coating exists as cubic phase formation and the diffraction peak intensities are higher than that of HA. As the ZrO2 content increasing, the bonding strength of coatings increases significantly. The ZrO2/HA composite coatings have superior wear resistance and lower friction coefficients compared with those of pure HA coating. The wear mechanisms of pure HA coating are ploughing and abrasive wear primarily, while the wear mechanisms of 15wt% ZrO2/HA composite coating and 30wt% ZrO2/HA composite coating are brittle spalling wear.
In order to investigate the friction and wear properties of ZrO2 reinforced hydroxyapatite (HA) composite coatings in bovine serum lubrication environment, HA bio-ceramic coatings whose ZrO2 contents were 0, 15wt% and 30wt% respectively were prepared on titanium alloy substrates by plasma spraying technology firstly. Then, the phase formation and bonding strength of ZrO2/HA composite coatings were analyzed. Finally, the friction and wear properties of ZrO2/HA composite coatings in bovine serum lubrication environment were investigated with UMT-3 pin-disk wear tester, the morphologies of wear surfaces of coatings were observed and the wear mechanisms were analyzed. The results show that the main phase of HA coatings are HA, the ZrO2 in 15wt% ZrO2/HA composite coating and 30wt% ZrO2/HA composite coating exists as cubic phase formation and the diffraction peak intensities are higher than that of HA. As the ZrO2 content increasing, the bonding strength of coatings increases significantly. The ZrO2/HA composite coatings have superior wear resistance and lower friction coefficients compared with those of pure HA coating. The wear mechanisms of pure HA coating are ploughing and abrasive wear primarily, while the wear mechanisms of 15wt% ZrO2/HA composite coating and 30wt% ZrO2/HA composite coating are brittle spalling wear.
2015, 32(6): 1784-1790.
doi: 10.13801/j.cnki.fhclxb.20150518.002
Abstract:
In order to reveal the effect laws of non-woven short fiber tissues on interlaminar fracture toughness of carbon fiber-reinforced polymer (CFRP) laminates, the mode I interlaminar fracture toughness of CFRP laminates toughened with non-woven carbon fiber tissues of different areal densities (1.95, 3.90, 7.80 and 15.60 mg/cm2) and different average lengths of fibers (0.8 mm and 4.3 mm) were investigated. The experimental results show that for the CFRP laminates toughened with different short fibers, the toughening performance of short fibers whose average length is 0.8 mm is better than that of short fibers whose average length is 4.3 mm, and the non-woven carbon fiber tissue with the areal density of 7.8 mg/cm2, thickness about 150 μm and average length of 0.8 mm significantly enhances the interlaminar fracture toughness of CFRP laminates, the energy release rate is improved by 99% at best comparing with that of unmodified CFRP laminate. The optical microscopy observation results show that the short fibers whose length is 0.8 mm have 3D interleaved structure in epoxy matrix, the structure can prevent the cracks form propagation effectively. SEM observation results indicate that the debonding and pullout of short fibers from epoxy matrix and plastic deformation of epoxy matrix around short fibers are the main toughening mechanisms of CFRP laminates. The research conclusions lay down the foundation for application of short fibers toughening technique for laminates.
In order to reveal the effect laws of non-woven short fiber tissues on interlaminar fracture toughness of carbon fiber-reinforced polymer (CFRP) laminates, the mode I interlaminar fracture toughness of CFRP laminates toughened with non-woven carbon fiber tissues of different areal densities (1.95, 3.90, 7.80 and 15.60 mg/cm2) and different average lengths of fibers (0.8 mm and 4.3 mm) were investigated. The experimental results show that for the CFRP laminates toughened with different short fibers, the toughening performance of short fibers whose average length is 0.8 mm is better than that of short fibers whose average length is 4.3 mm, and the non-woven carbon fiber tissue with the areal density of 7.8 mg/cm2, thickness about 150 μm and average length of 0.8 mm significantly enhances the interlaminar fracture toughness of CFRP laminates, the energy release rate is improved by 99% at best comparing with that of unmodified CFRP laminate. The optical microscopy observation results show that the short fibers whose length is 0.8 mm have 3D interleaved structure in epoxy matrix, the structure can prevent the cracks form propagation effectively. SEM observation results indicate that the debonding and pullout of short fibers from epoxy matrix and plastic deformation of epoxy matrix around short fibers are the main toughening mechanisms of CFRP laminates. The research conclusions lay down the foundation for application of short fibers toughening technique for laminates.
2015, 32(6): 1791-1799.
doi: 10.13801/j.cnki.fhclxb.20150325.004
Abstract:
In order to estimate the effects of thermoplasticity crystalline polymer polyvinylidene fluoride (PVDF) on dynamic mechanical and damping properties of co-cured composites, PVDF was loaded on aramid nonwoven fabric (ANF), and PVDF-ANF/epoxy (EP) structural damping composites were fabricated by co-cured process firstly. Then, the temperature spectra of loss factor, loss modulus and storage modulus were tested through dynamic mechanical analyzer; flexural strength, flexural modulus and interlaminar shear strength were measured to evaluate the static mechanical properties of the composites; the resonant frequencies and decaying curves of free vibration were tested by single cantilever beam vibration experiment and the loss factors were calculated; the fracture toughness and toughening mechanisms were investigated by type I and type II interlaminar fracture toughness experiments as well as the observation of fracture surface micro morphologies. At last, the microstructure of the composites were analyzed to discuss the structural internal reasons for having both mechanical properties and damping properties. The results indicate that the damping properties and interlaminar fracture toughness of PVDF-ANF/EP composites can be improved further more by loading PVDF on the surfaces of ANF without leading to an obvious decrease of mechanical properties of the composite. The loss factor of composite is improved by 33.3%, and the fracture toughness of type I and type II are improved by 168% and 208%, respectively.
In order to estimate the effects of thermoplasticity crystalline polymer polyvinylidene fluoride (PVDF) on dynamic mechanical and damping properties of co-cured composites, PVDF was loaded on aramid nonwoven fabric (ANF), and PVDF-ANF/epoxy (EP) structural damping composites were fabricated by co-cured process firstly. Then, the temperature spectra of loss factor, loss modulus and storage modulus were tested through dynamic mechanical analyzer; flexural strength, flexural modulus and interlaminar shear strength were measured to evaluate the static mechanical properties of the composites; the resonant frequencies and decaying curves of free vibration were tested by single cantilever beam vibration experiment and the loss factors were calculated; the fracture toughness and toughening mechanisms were investigated by type I and type II interlaminar fracture toughness experiments as well as the observation of fracture surface micro morphologies. At last, the microstructure of the composites were analyzed to discuss the structural internal reasons for having both mechanical properties and damping properties. The results indicate that the damping properties and interlaminar fracture toughness of PVDF-ANF/EP composites can be improved further more by loading PVDF on the surfaces of ANF without leading to an obvious decrease of mechanical properties of the composite. The loss factor of composite is improved by 33.3%, and the fracture toughness of type I and type II are improved by 168% and 208%, respectively.
2015, 32(6): 1800-1806.
doi: 10.13801/j.cnki.fhclxb.20150204.001
Abstract:
In order to further improve the bone inductive properties of bone repair materials, BaTiO3piezoelectric coating was introduced.First, three kinds of biological coatings of hydroxyapatite (HA), Ti-HA and Ti-HA-BaTiO3 were prepared on Ti substrates by plasma spraying method. Then, the spray process parameters were optimized by orthogonal test design, the morphology and composition of coatings were characterized by SEM/EDS, and the bonding strength between coating and substrate was tested by scratch test. Finally, the cell culture test was conducted, the cytotoxicity was evaluated by CCK-8 method, and the adhesion morphology of cells was observed under SEM. The results show that cells have pseudopodia, present fusiform and irregular polygons, and adhere to the surface of Ti-HA-BaTiO3 composite coating; cells spread in good shape, the cytotoxicity level of coating is no higher than Level 1.It follows that Ti-HA-BaTiO3bio-composites can be used as clinical implant materials.
In order to further improve the bone inductive properties of bone repair materials, BaTiO3piezoelectric coating was introduced.First, three kinds of biological coatings of hydroxyapatite (HA), Ti-HA and Ti-HA-BaTiO3 were prepared on Ti substrates by plasma spraying method. Then, the spray process parameters were optimized by orthogonal test design, the morphology and composition of coatings were characterized by SEM/EDS, and the bonding strength between coating and substrate was tested by scratch test. Finally, the cell culture test was conducted, the cytotoxicity was evaluated by CCK-8 method, and the adhesion morphology of cells was observed under SEM. The results show that cells have pseudopodia, present fusiform and irregular polygons, and adhere to the surface of Ti-HA-BaTiO3 composite coating; cells spread in good shape, the cytotoxicity level of coating is no higher than Level 1.It follows that Ti-HA-BaTiO3bio-composites can be used as clinical implant materials.
2015, 32(6): 1807-1813.
doi: 10.13801/j.cnki.fhclxb.20150302.004
Abstract:
In order to obtain the polymer porous materials with excellent performances, under the existence of end-capping reagent hexamethyldisiloxane (MM), MTQ organic silicone resin with methacryloxypropyl functional group was prepared by hydrolytic condensation polymerization reaction between sodium silicate and methacryloxypropyltrimethoxylsilane (MPS) firstly. Then, the MTQ silicone resin was used as crosslinking agent and 2-ethylhexyl acrylate (EHA) was used as monomer, MTQ silicone resin/poly 2-ethylhexyl acrylate (PEHA) polymer porous materials were prepared by high internal phase emulsions template method. Finally, the pore structure, compressive properties and thermal stability of the porous materials were investigated. The results show that the voids diameter of MTQ silicone resin/PEHA polymer porous materials prepared by using MTQ silicone resin as crosslinking agent is in the range of 4-10 μm, and the pores diameter distributes in the range of 0.3-2.0 μm. All of the voids are linked closely, the pores are uniform distributed and the channels are narrow. MTQ silicone resin content has little effects on the specific surface area and pore volume of MTQ silicone resin/PEHA polymer porous materials, but can enhance the thermal stability and compressive strength of polymer porous materials significantly, the temperature of maximum thermal decomposition rate is up to 411.5 ℃ under nitrogen atmosphere.
In order to obtain the polymer porous materials with excellent performances, under the existence of end-capping reagent hexamethyldisiloxane (MM), MTQ organic silicone resin with methacryloxypropyl functional group was prepared by hydrolytic condensation polymerization reaction between sodium silicate and methacryloxypropyltrimethoxylsilane (MPS) firstly. Then, the MTQ silicone resin was used as crosslinking agent and 2-ethylhexyl acrylate (EHA) was used as monomer, MTQ silicone resin/poly 2-ethylhexyl acrylate (PEHA) polymer porous materials were prepared by high internal phase emulsions template method. Finally, the pore structure, compressive properties and thermal stability of the porous materials were investigated. The results show that the voids diameter of MTQ silicone resin/PEHA polymer porous materials prepared by using MTQ silicone resin as crosslinking agent is in the range of 4-10 μm, and the pores diameter distributes in the range of 0.3-2.0 μm. All of the voids are linked closely, the pores are uniform distributed and the channels are narrow. MTQ silicone resin content has little effects on the specific surface area and pore volume of MTQ silicone resin/PEHA polymer porous materials, but can enhance the thermal stability and compressive strength of polymer porous materials significantly, the temperature of maximum thermal decomposition rate is up to 411.5 ℃ under nitrogen atmosphere.
2015, 32(6): 1814-1823.
doi: 10.13801/j.cnki.fhclxb.20150306.001
Abstract:
Composite laminate modeling based on lamination parameters is fulfilled and the parameter input problem of lamination parameters with Natran is solved, using a simple numerical example to demonstrate its validity. With composite laminate modeling method based on lamination parameters and p-k method for calculation of flutter and divergence speeds, flutter and divergence characteristics of a cantilevered laminate are studied using lamination parameters. The effects of principal-axis stiffness and bending-torsional coupling on the flutter speed are emphasized The results show that compared with the bending stiffness, change of torsional stiffness has a more obvious influence on flutter speed. And the flutter speed decreases with decrease of torsional stiffness. The switch of flutter mode may occur due to change of stiffness, which leads to interrupt change of flutter speed and discontinuity of flutter speed contours in lamination parameter plane. With constant normalized stiffness matrix, the flutter and divergence speeds can be improved and have a linearity relationship with the laminate thickness.
Composite laminate modeling based on lamination parameters is fulfilled and the parameter input problem of lamination parameters with Natran is solved, using a simple numerical example to demonstrate its validity. With composite laminate modeling method based on lamination parameters and p-k method for calculation of flutter and divergence speeds, flutter and divergence characteristics of a cantilevered laminate are studied using lamination parameters. The effects of principal-axis stiffness and bending-torsional coupling on the flutter speed are emphasized The results show that compared with the bending stiffness, change of torsional stiffness has a more obvious influence on flutter speed. And the flutter speed decreases with decrease of torsional stiffness. The switch of flutter mode may occur due to change of stiffness, which leads to interrupt change of flutter speed and discontinuity of flutter speed contours in lamination parameter plane. With constant normalized stiffness matrix, the flutter and divergence speeds can be improved and have a linearity relationship with the laminate thickness.
2015, 32(6): 1824-1834.
doi: 10.13801/j.cnki.fhclxb.20150316.004
Abstract:
1Cr18Ni9Ti and Ti-6Al-4V were selected as the metal substrates, and CrO3+Al thermit was introduced into B4C+Ti primary system for adjusting the adiabatic temperature of reaction system as 3 193, 3 282, 3 290 and 3 473 K, TiB2-TiC/1Cr18Ni9Ti and TiB2-TiC/Ti-6Al-4V graded composites were prepared by reaction joining in high-gravity field. Because increasing reaction adiabatic temperature brought about the increased melting depth of metal substrates, the intermediate between the ceramic and metal increased in thickness while Al2O3 inclusions at the interfacial areas inevitably increased. By changing the processing route, i.e. respectively preparing, ball-milling and compacting B4C+Ti blends and CrO3+Al thermit and subsequently filling them one by one into the crucibles, it is found that Al2O3 inclusions at the intermediates are removed completely, three-dimensional network ceramic/metal graded composite structure develope in the interface of TiB2-TiC/1Cr18Ni9Ti, while in the interface of TiB2-TiC/Ti-6Al-4V there forms the multiscale and multilevel graded composite structure.
1Cr18Ni9Ti and Ti-6Al-4V were selected as the metal substrates, and CrO3+Al thermit was introduced into B4C+Ti primary system for adjusting the adiabatic temperature of reaction system as 3 193, 3 282, 3 290 and 3 473 K, TiB2-TiC/1Cr18Ni9Ti and TiB2-TiC/Ti-6Al-4V graded composites were prepared by reaction joining in high-gravity field. Because increasing reaction adiabatic temperature brought about the increased melting depth of metal substrates, the intermediate between the ceramic and metal increased in thickness while Al2O3 inclusions at the interfacial areas inevitably increased. By changing the processing route, i.e. respectively preparing, ball-milling and compacting B4C+Ti blends and CrO3+Al thermit and subsequently filling them one by one into the crucibles, it is found that Al2O3 inclusions at the intermediates are removed completely, three-dimensional network ceramic/metal graded composite structure develope in the interface of TiB2-TiC/1Cr18Ni9Ti, while in the interface of TiB2-TiC/Ti-6Al-4V there forms the multiscale and multilevel graded composite structure.
