2017 Vol. 34, No. 4
2017, 34(4): 699-707.
doi: 10.13801/j.cnki.fhclxb.20161208.003
Abstract:
The graphene oxide (GO) synthesized by Hummers' method was mixed into coupled product nano SiO2-NH2 obtained by silane coupling agent (APTES) modifying nano SiO2 to prepare nano SiO2 functionally modified graphene sheet composites (nano SiO2-g-GS) through the graphene sheets grafting with nano SiO2. The nano SiO2 functionally modified graphene/thermoplastic polyurethane composites (nano SiO2-g-GS/TPU) were fabricated by melt compounding method using the thermoplastic polyurethane (TPU) as the matrix and nano SiO2-g-GS as the filler, and then the fillers and composites were systematically characterized. The tensile tests show that the stress at definite elongation (300%, 500%, 1 000%) of nano SiO2-g-GS/TPU composites increases due to nano SiO2-g-GS has strengthening effects on the TPU. DSC tests show that the crystallinity temperature of the nano SiO2-g-GS/TPU composites increases significantly compared with pure TPU, and the crystallinity temperature of TPU with 1wt% mass fraction of nano SiO2-g-GS increases by 44℃. The shape memory testing results show that the shape recovery ratio (Rr) of nano SiO2-g-GS/TPU decreases and the shape fixing ratio (Rf) increases with the increase of the mass fraction of nano SiO2-g-GS. The nano SiO2-g-GS/TPU composites with 1 wt% nano SiO2-g-GS exhibit the best performance.
The graphene oxide (GO) synthesized by Hummers' method was mixed into coupled product nano SiO2-NH2 obtained by silane coupling agent (APTES) modifying nano SiO2 to prepare nano SiO2 functionally modified graphene sheet composites (nano SiO2-g-GS) through the graphene sheets grafting with nano SiO2. The nano SiO2 functionally modified graphene/thermoplastic polyurethane composites (nano SiO2-g-GS/TPU) were fabricated by melt compounding method using the thermoplastic polyurethane (TPU) as the matrix and nano SiO2-g-GS as the filler, and then the fillers and composites were systematically characterized. The tensile tests show that the stress at definite elongation (300%, 500%, 1 000%) of nano SiO2-g-GS/TPU composites increases due to nano SiO2-g-GS has strengthening effects on the TPU. DSC tests show that the crystallinity temperature of the nano SiO2-g-GS/TPU composites increases significantly compared with pure TPU, and the crystallinity temperature of TPU with 1wt% mass fraction of nano SiO2-g-GS increases by 44℃. The shape memory testing results show that the shape recovery ratio (Rr) of nano SiO2-g-GS/TPU decreases and the shape fixing ratio (Rf) increases with the increase of the mass fraction of nano SiO2-g-GS. The nano SiO2-g-GS/TPU composites with 1 wt% nano SiO2-g-GS exhibit the best performance.
2017, 34(4): 708-713.
doi: 10.13801/j.cnki.fhclxb.20160819.001
Abstract:
Cellulose nanofibers (CNFs) were prepared by the combined method of acid alkali treatment and mechanical grinding. Polyvinyl alcohol (PVA), CNFs/PVA, PVA and CNFs/PVA modified by polyethylene glycol (PEG) composite hydrogels were prepared by the freezing/thawing method. The microstructure, swelling property, compressive strength and thermal stability of the PVA composite hydrogels were studied. The results show that the microstructure of PVA hydrogels is perfected by CNFs and PEG. After adding PEG, PEG/PVA composite hydrogel has obvious 3D network. When both PEG and CNFs are added into the PVA hydrogel, the obtained CNFs-PEG/PVA hydrogel forms a uniform network structure. The porosity and swelling degree of the CNFs-PEG/PVA hydrogel reach up to (67.5±4.3)% and 980%, respectively. Compared with the pure PVA hydrogel, the compressive strength of CNFs-PEG/PVA hydrogel also increases. The addition of PEG has no effect on the thermal stability of the PVA hydrogel, but the addition of CNFs significantly improves the thermal stability of CNFs-PEG/PVA hydrogel, and the initial thermal decomposition temperature of CNFs-PEG/PVA composite hydrogel increases from 235℃ to 300℃.
Cellulose nanofibers (CNFs) were prepared by the combined method of acid alkali treatment and mechanical grinding. Polyvinyl alcohol (PVA), CNFs/PVA, PVA and CNFs/PVA modified by polyethylene glycol (PEG) composite hydrogels were prepared by the freezing/thawing method. The microstructure, swelling property, compressive strength and thermal stability of the PVA composite hydrogels were studied. The results show that the microstructure of PVA hydrogels is perfected by CNFs and PEG. After adding PEG, PEG/PVA composite hydrogel has obvious 3D network. When both PEG and CNFs are added into the PVA hydrogel, the obtained CNFs-PEG/PVA hydrogel forms a uniform network structure. The porosity and swelling degree of the CNFs-PEG/PVA hydrogel reach up to (67.5±4.3)% and 980%, respectively. Compared with the pure PVA hydrogel, the compressive strength of CNFs-PEG/PVA hydrogel also increases. The addition of PEG has no effect on the thermal stability of the PVA hydrogel, but the addition of CNFs significantly improves the thermal stability of CNFs-PEG/PVA hydrogel, and the initial thermal decomposition temperature of CNFs-PEG/PVA composite hydrogel increases from 235℃ to 300℃.
2017, 34(4): 714-722.
doi: 10.13801/j.cnki.fhclxb.20160711.002
Abstract:
In order to investigate the effects of polyethylene glycol (PEG) on the properties of cellulose nanocrystals (CNCs)/poly 3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV) composites, polyethylene glycol (PEG)-CNCs/PHBV composites were prepared by the melt compounding method. The facture structure, crystalline properties, thermal stability, and mechanical properties of PEG-CNCs/PHBV composites were charactered by ESEM, DSC, POM, TG and material-testing machine, respectively. The results show that the cross section of CNCs/PHBV composites with the addition of PEG becomes rough and fracture suface becomes uneven. The addition of PEG make the spherulite sizes of PEG-CNCs/PHBV composites decrease, new spherulite structure defects emerge, and melting process transform into two melting peaks. The melt temperature Tm decreases from 167.8℃ to 165.1℃. In addition, the addition of PEG enhances the mobility of PHBV molecular chain, thus the crystallization of PHBV becomes more difficult. The melt crystalline temperature Tmc of composites decreases from 99.8℃ to 73.5℃ and the crystallinity Xc decreases from 54.3% to 50.2%. Compared with PHBV, the impact strength and tensile elongation at break of PEG-CNCs/PHBV composites keep increasing with the increase of PEG content, whose maximal promotion with 25wt% PEG are 56.4% and 96.3%, respectively, but the Young's modulus and tensile strength of PEG-CNCs/PHBV composites keep decreasing. Meanwhile the application of PEG improves the thermal stability of composite materials. The pyrolysis process of PEG-CNCs/PHBV composites transforms into two steps, and the fastest decomposition temperature (Tmax1) in the first and second step increases from 281.5℃ to 285.3℃, and from 371.5℃ to 394.3℃, respectively. The addition of PEG can improve the compatibilization and crystallinity between CNCs and PHBV, accordingly enhance toughness, plasticity and thermal stabilities of CNCs/PHBV composites.
In order to investigate the effects of polyethylene glycol (PEG) on the properties of cellulose nanocrystals (CNCs)/poly 3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV) composites, polyethylene glycol (PEG)-CNCs/PHBV composites were prepared by the melt compounding method. The facture structure, crystalline properties, thermal stability, and mechanical properties of PEG-CNCs/PHBV composites were charactered by ESEM, DSC, POM, TG and material-testing machine, respectively. The results show that the cross section of CNCs/PHBV composites with the addition of PEG becomes rough and fracture suface becomes uneven. The addition of PEG make the spherulite sizes of PEG-CNCs/PHBV composites decrease, new spherulite structure defects emerge, and melting process transform into two melting peaks. The melt temperature Tm decreases from 167.8℃ to 165.1℃. In addition, the addition of PEG enhances the mobility of PHBV molecular chain, thus the crystallization of PHBV becomes more difficult. The melt crystalline temperature Tmc of composites decreases from 99.8℃ to 73.5℃ and the crystallinity Xc decreases from 54.3% to 50.2%. Compared with PHBV, the impact strength and tensile elongation at break of PEG-CNCs/PHBV composites keep increasing with the increase of PEG content, whose maximal promotion with 25wt% PEG are 56.4% and 96.3%, respectively, but the Young's modulus and tensile strength of PEG-CNCs/PHBV composites keep decreasing. Meanwhile the application of PEG improves the thermal stability of composite materials. The pyrolysis process of PEG-CNCs/PHBV composites transforms into two steps, and the fastest decomposition temperature (Tmax1) in the first and second step increases from 281.5℃ to 285.3℃, and from 371.5℃ to 394.3℃, respectively. The addition of PEG can improve the compatibilization and crystallinity between CNCs and PHBV, accordingly enhance toughness, plasticity and thermal stabilities of CNCs/PHBV composites.
2017, 34(4): 723-729.
doi: 10.13801/j.cnki.fhclxb.20160706.002
Abstract:
The modified diatomite was used as the main filler, polypropylene(PP) resin as the matrix, epoxidized soybean oil (ESO) as the plasticizer and heat stabilizer, the modified diatomite-ESO/PP composites were prepared by melting blending method. The factors of influence and strengthen toughening mechanism was analyzed by XRD, SEM, optical microscope (OM), polarizing microscope (PLM) and mechanical properties test. The results show the space grid structure of the modified diatomite-ESO/PP can be formed through the combination of physical crosslinking or chemical grafting among the interface of diatomite, ESO and PP, and diatomite can disperse in PP matrix uniformly. When modified diatomite mass ratio remains invariability, with the increase of ESO content, the flexural strength of the modified diatomite-ESO/PP decreases slightly, but the impact strength and hardness increase. With 20% mass ratio to PP of modified diatomite and 2.5% mass ratio to PP of ESO, the modified diatomite-ESO/PP composite with optimal mechanical properties can be obtained. The reinforcement of the modified diatomite-ESO/PP is mainly beacause that the modified diatomite has some characteristics such as a high modulus, the heterodromous nucleation in the polymer melt promoting the crystal of PP, a better interfacial adhesion with matrix, and a good dispersibility. ESO can insert into polymer molecular chains, weak the mobility among the polymer molecular chains, and to a certain extent reduce the crystallization of the matrix, which lead to improve the toughness of PP matrix. Due to the modified diatomite adding to the PP matrix, α crystal of PP transferms into β crystal of PP with higher impact strength, thus the modified diatomite and ESO can work cooperatively and achieve reinforcing and toughening of the modified diatomite-ESO/PP composite. However, more adding of ESO makes the modified diatomite focus on the surface of composites, and results in the increase of the surface hardness of the modified diatomite-ESO/PP composite.
The modified diatomite was used as the main filler, polypropylene(PP) resin as the matrix, epoxidized soybean oil (ESO) as the plasticizer and heat stabilizer, the modified diatomite-ESO/PP composites were prepared by melting blending method. The factors of influence and strengthen toughening mechanism was analyzed by XRD, SEM, optical microscope (OM), polarizing microscope (PLM) and mechanical properties test. The results show the space grid structure of the modified diatomite-ESO/PP can be formed through the combination of physical crosslinking or chemical grafting among the interface of diatomite, ESO and PP, and diatomite can disperse in PP matrix uniformly. When modified diatomite mass ratio remains invariability, with the increase of ESO content, the flexural strength of the modified diatomite-ESO/PP decreases slightly, but the impact strength and hardness increase. With 20% mass ratio to PP of modified diatomite and 2.5% mass ratio to PP of ESO, the modified diatomite-ESO/PP composite with optimal mechanical properties can be obtained. The reinforcement of the modified diatomite-ESO/PP is mainly beacause that the modified diatomite has some characteristics such as a high modulus, the heterodromous nucleation in the polymer melt promoting the crystal of PP, a better interfacial adhesion with matrix, and a good dispersibility. ESO can insert into polymer molecular chains, weak the mobility among the polymer molecular chains, and to a certain extent reduce the crystallization of the matrix, which lead to improve the toughness of PP matrix. Due to the modified diatomite adding to the PP matrix, α crystal of PP transferms into β crystal of PP with higher impact strength, thus the modified diatomite and ESO can work cooperatively and achieve reinforcing and toughening of the modified diatomite-ESO/PP composite. However, more adding of ESO makes the modified diatomite focus on the surface of composites, and results in the increase of the surface hardness of the modified diatomite-ESO/PP composite.
2017, 34(4): 730-736.
doi: 10.13801/j.cnki.fhclxb.20160819.002
Abstract:
By adding graphene oxide(GO) or graphite(G) in blending system of nitrile rubber(NBR) and polyurethane(PU), the GO/NBR-PU and G/NBR-PU ternary composites were prepared by the technology of hot-press moulding. The dynamic mechanic property of the GO/NBR-PU and G/NBR-PU composites were studied by DMA, FTIR, SEM and so on. The results suggest that the tangent of loss angle(tanδ), the storage modulus(E') and the loss modulus(E") of the GO/NBR-PU composites all present a trend of increasing originally and decreasing subsequently with the increase of GO content. At the same time, when the mass ratio of GO to NBR reach its critical value 3%, the composites have superior dynamic mechanic performances. As the graphite is added, the damping property and mechanical properties of the composites are enhanced, but the mechanical properties of the composites decrease with the increasing of more graphite content. Through microscopic analysis, the enhancement function of GO is mainly due to the interfacial effect. The main reason for the decrease of mechanical properties is the agglomeration of GO or graphite in NBR-PU composites.
By adding graphene oxide(GO) or graphite(G) in blending system of nitrile rubber(NBR) and polyurethane(PU), the GO/NBR-PU and G/NBR-PU ternary composites were prepared by the technology of hot-press moulding. The dynamic mechanic property of the GO/NBR-PU and G/NBR-PU composites were studied by DMA, FTIR, SEM and so on. The results suggest that the tangent of loss angle(tanδ), the storage modulus(E') and the loss modulus(E") of the GO/NBR-PU composites all present a trend of increasing originally and decreasing subsequently with the increase of GO content. At the same time, when the mass ratio of GO to NBR reach its critical value 3%, the composites have superior dynamic mechanic performances. As the graphite is added, the damping property and mechanical properties of the composites are enhanced, but the mechanical properties of the composites decrease with the increasing of more graphite content. Through microscopic analysis, the enhancement function of GO is mainly due to the interfacial effect. The main reason for the decrease of mechanical properties is the agglomeration of GO or graphite in NBR-PU composites.
2017, 34(4): 737-743.
doi: 10.13801/j.cnki.fhclxb.20160630.002
Abstract:
The effects of bismaleimide tackifier with different contents on the styling effects, liquid composite molding processes and mechanical performances of the 0°/90° biaxial non-crimp fabric (NCF) were mianly studied. The thickness springback and C type springback researches were used to characterize the styling effects. The thickness compress and the bias extension test methods were used to characterize molding processes of NCF. And three-point bending experiment and interlaminar shear test were conducted on the mechanical properties of NCF. The experimental results show that bismaleimide tackifier plays significant styling effects on preform. The in-plane shear properties and the resistance of shear deformation of NCF with tackifier are obviously improved. The addition of tackifier has little effects on mechanical properties of the 0°/90° biaxial NCF. Tackifier can improve the performances of liquid composite molding processes of NCF, and preserve mechanical properties of the composites at the same time.
The effects of bismaleimide tackifier with different contents on the styling effects, liquid composite molding processes and mechanical performances of the 0°/90° biaxial non-crimp fabric (NCF) were mianly studied. The thickness springback and C type springback researches were used to characterize the styling effects. The thickness compress and the bias extension test methods were used to characterize molding processes of NCF. And three-point bending experiment and interlaminar shear test were conducted on the mechanical properties of NCF. The experimental results show that bismaleimide tackifier plays significant styling effects on preform. The in-plane shear properties and the resistance of shear deformation of NCF with tackifier are obviously improved. The addition of tackifier has little effects on mechanical properties of the 0°/90° biaxial NCF. Tackifier can improve the performances of liquid composite molding processes of NCF, and preserve mechanical properties of the composites at the same time.
2017, 34(4): 744-748.
doi: 10.13801/j.cnki.fhclxb.20161024.005
Abstract:
Based on the experience of hot sizing process for metals, the high-temperature stress relaxation phenomenon of composites was utilized to rectify the profile of composite structures using the hot sizing process. L-shaped and C-shaped beams made of carbon fiber fabric/epoxy were manufactured. The hot sizing experiments were carried out using the homemade hot sizing tools to investigate the effect of hot sizing load and hot sizing period on the shape of the part. The feasibility of the hot sizing process for carbon fiber fabric/epoxy composite structures was also analyzed. It is found that the stress relaxation under high temperature is the major factor to induce deformation of the composite structure in the hot sizing process, and other factors can be neglected. Both hot sizing load and hot sizing period have great influences on the result of the hot sizing process. As for a certain composite structure, an appropriate hot sizing process can effectively control the shape of the structure and make the assembly of the part more convenient.
Based on the experience of hot sizing process for metals, the high-temperature stress relaxation phenomenon of composites was utilized to rectify the profile of composite structures using the hot sizing process. L-shaped and C-shaped beams made of carbon fiber fabric/epoxy were manufactured. The hot sizing experiments were carried out using the homemade hot sizing tools to investigate the effect of hot sizing load and hot sizing period on the shape of the part. The feasibility of the hot sizing process for carbon fiber fabric/epoxy composite structures was also analyzed. It is found that the stress relaxation under high temperature is the major factor to induce deformation of the composite structure in the hot sizing process, and other factors can be neglected. Both hot sizing load and hot sizing period have great influences on the result of the hot sizing process. As for a certain composite structure, an appropriate hot sizing process can effectively control the shape of the structure and make the assembly of the part more convenient.
2017, 34(4): 749-757.
doi: 10.13801/j.cnki.fhclxb.20160823.001
Abstract:
In order to investigate the wear mechanism and variational law at the different cutting edges of the cutting tool used for machining carbon fiber reinforced plastics (CFRP), based on the typical tungsten carbide double point angle drill, the wear mechanism and law of influence on the hole-exit delamination at the chisel edge and influence on the final drilling quality at the secondary cutting edge were analyzed, respectively. By reducing wear measurement interval of the drill bit, and introducing the values of cutting edge rounding and flank wear width, the wear recession of the chisel edge and the secondary cutting edge in the drilling were characterized. By means of the microscope measurement of the cutting edge and the calculation of cutting edge rounding, it is found that chipping is dominant at the chisel edge and secondary cutting edge is reground and re-sharpened after flank wear. The wear law of this type of double point angle drill was also obtained, and the effects of wearing capacity on thrust force and drilling torque were analyzed based on the tool wear results. The results show that thrust force caused by the chisel edge has weak correlation with the cutting edge rounding of chisel edge, and the drilling torque corresponds well with the flank wear of the secondary cutting edge.
In order to investigate the wear mechanism and variational law at the different cutting edges of the cutting tool used for machining carbon fiber reinforced plastics (CFRP), based on the typical tungsten carbide double point angle drill, the wear mechanism and law of influence on the hole-exit delamination at the chisel edge and influence on the final drilling quality at the secondary cutting edge were analyzed, respectively. By reducing wear measurement interval of the drill bit, and introducing the values of cutting edge rounding and flank wear width, the wear recession of the chisel edge and the secondary cutting edge in the drilling were characterized. By means of the microscope measurement of the cutting edge and the calculation of cutting edge rounding, it is found that chipping is dominant at the chisel edge and secondary cutting edge is reground and re-sharpened after flank wear. The wear law of this type of double point angle drill was also obtained, and the effects of wearing capacity on thrust force and drilling torque were analyzed based on the tool wear results. The results show that thrust force caused by the chisel edge has weak correlation with the cutting edge rounding of chisel edge, and the drilling torque corresponds well with the flank wear of the secondary cutting edge.
2017, 34(4): 758-765.
doi: 10.13801/j.cnki.fhclxb.20160630.003
Abstract:
According to the same layup structure, the axial compression and flexural properties of the unidirectional inter-layer carbon-glass hybrid composite with various hybrid ratios were inverstigated. The carbon fibers were introduced into the warp knitted glass fiber fabric. It is found that the carbon fibers can improve the strength and modulus of the axial compression and flexure in the hybrid composites. Compared with the pure glass fiber, the axial compressed strength of the hybrid composites with three different hybrid ratios increase by 22.72%, 26.95% and 11.43%, respectively. Different hybrid ratios bring about different damge modes. The axial compressed and flexural modulus of the hybrid composites both increase with the increase of the carbon fiber content. The flexural strength of the hybrid composites with different hybrid ratios keep consistent and increase unobviously.
According to the same layup structure, the axial compression and flexural properties of the unidirectional inter-layer carbon-glass hybrid composite with various hybrid ratios were inverstigated. The carbon fibers were introduced into the warp knitted glass fiber fabric. It is found that the carbon fibers can improve the strength and modulus of the axial compression and flexure in the hybrid composites. Compared with the pure glass fiber, the axial compressed strength of the hybrid composites with three different hybrid ratios increase by 22.72%, 26.95% and 11.43%, respectively. Different hybrid ratios bring about different damge modes. The axial compressed and flexural modulus of the hybrid composites both increase with the increase of the carbon fiber content. The flexural strength of the hybrid composites with different hybrid ratios keep consistent and increase unobviously.
2017, 34(4): 766-772.
doi: 10.13801/j.cnki.fhclxb.20160729.002
Abstract:
Based on the new couple stress theory, a new model of plane orthotropic functionally graded beam model was proposed. The two material scale parameters included in the model enables present model to describe different bending stiffness enhancements in two orthogonal directions caused by scale effect. The equilibrium equations and related boundary conditions were derived using the principle of minimum potential energy. Analytical solution of bending problem was developed for a bending cantilever beam with concentrate force applied on the free end. The governing equations and solutions of present model have similar form with classical beam model, except one additional term related to scale effect in rigidity. Numerical results indicate that deflection of the beam predicted by present model is smaller than that of the classical one, which means the scale effect can be captured. The scale effect will increase with the decrease of the geometrical size of the beam, but diminish little by little when the geometrical size is much larger than the material scale parameter.
Based on the new couple stress theory, a new model of plane orthotropic functionally graded beam model was proposed. The two material scale parameters included in the model enables present model to describe different bending stiffness enhancements in two orthogonal directions caused by scale effect. The equilibrium equations and related boundary conditions were derived using the principle of minimum potential energy. Analytical solution of bending problem was developed for a bending cantilever beam with concentrate force applied on the free end. The governing equations and solutions of present model have similar form with classical beam model, except one additional term related to scale effect in rigidity. Numerical results indicate that deflection of the beam predicted by present model is smaller than that of the classical one, which means the scale effect can be captured. The scale effect will increase with the decrease of the geometrical size of the beam, but diminish little by little when the geometrical size is much larger than the material scale parameter.
2017, 34(4): 773-785.
doi: 10.13801/j.cnki.fhclxb.20160721.001
Abstract:
Based on the framework of continuum damage mechanics and plasticity theory, a combined elastoplastic damage model which takes into account the plasticity effects and material properties degradation due to damage development was developed. Based on the closest point projection return mapping algorithm, a strain-driven implicit integration algorithm for the model was developed to update stresses and solution dependent state variables. A tangent stiffness tensor consistent with the developed numerical algorithm was derived to ensure the computational efficiency of Newton-Raphson method in the finite element analysis. In order to alleviate mesh dependency of finite element analysis results, the "Crack Band Theory" was applied to regularize the softening branch of the material model. Also, in order to avoid premature abortion of numerical analysis using strain softening material models based on implicit procedures, a viscous regularization scheme was applied to the damage parameters. Accordingly, the regularized numerical consistent tangent tensor was derived. User-defined material subroutine UMAT containing the numerical integration algorithm was coded and implemented in finite element procedure Abaqus v6.14. The efficiency of the material constitutive model was demonstrated through progressive failure analysis of a V-notched AS4/3501-6 composite laminate, the mechanical behavior of which demonstrates significant plasticity effects. The predicted results agree well with the experimental data reported in the literature and the developed model outperforms other existing elastic-damage models in predicting the failure loads. The result shows that the combined elastoplastic damage model can predict the mechanical behavior of composite materials which exhibit pronounced plasticity effects with sufficient accuracy. The proposed approach provides an efficient method for composite component and structural design.
Based on the framework of continuum damage mechanics and plasticity theory, a combined elastoplastic damage model which takes into account the plasticity effects and material properties degradation due to damage development was developed. Based on the closest point projection return mapping algorithm, a strain-driven implicit integration algorithm for the model was developed to update stresses and solution dependent state variables. A tangent stiffness tensor consistent with the developed numerical algorithm was derived to ensure the computational efficiency of Newton-Raphson method in the finite element analysis. In order to alleviate mesh dependency of finite element analysis results, the "Crack Band Theory" was applied to regularize the softening branch of the material model. Also, in order to avoid premature abortion of numerical analysis using strain softening material models based on implicit procedures, a viscous regularization scheme was applied to the damage parameters. Accordingly, the regularized numerical consistent tangent tensor was derived. User-defined material subroutine UMAT containing the numerical integration algorithm was coded and implemented in finite element procedure Abaqus v6.14. The efficiency of the material constitutive model was demonstrated through progressive failure analysis of a V-notched AS4/3501-6 composite laminate, the mechanical behavior of which demonstrates significant plasticity effects. The predicted results agree well with the experimental data reported in the literature and the developed model outperforms other existing elastic-damage models in predicting the failure loads. The result shows that the combined elastoplastic damage model can predict the mechanical behavior of composite materials which exhibit pronounced plasticity effects with sufficient accuracy. The proposed approach provides an efficient method for composite component and structural design.
2017, 34(4): 786-794.
doi: 10.13801/j.cnki.fhclxb.20160630.001
Abstract:
For strength analysis of thick composite laminate, a multi-scale model based on sub-laminate stiffness homogenizing and stress/strain decomposition was introduced, in which the shear nonlinearity was also considered. In this way, the thick laminate could be modelled at a sub-laminate level and the structural failure could be predicted at a ply level. A user-defined FORTRAN subroutine (VUMAT) was written to model the shear nonlinearity and intra-laminar failure, and the cohesive zone model was introduced to predict the delamination between two sub-laminates. The strength and structural response of G13 out-of-plane shear test were predicted with both multi-scale linear and non-linear model. By comparison with the experimental results, it is found that the multi-scale linear model works well in predicting structural load capacity, but significantly differs from experimental results when predicting the global load-displacement response. For multi-scale non-linear model, both the failure mode and the load-displacement curve fit well with the experimental results.
For strength analysis of thick composite laminate, a multi-scale model based on sub-laminate stiffness homogenizing and stress/strain decomposition was introduced, in which the shear nonlinearity was also considered. In this way, the thick laminate could be modelled at a sub-laminate level and the structural failure could be predicted at a ply level. A user-defined FORTRAN subroutine (VUMAT) was written to model the shear nonlinearity and intra-laminar failure, and the cohesive zone model was introduced to predict the delamination between two sub-laminates. The strength and structural response of G13 out-of-plane shear test were predicted with both multi-scale linear and non-linear model. By comparison with the experimental results, it is found that the multi-scale linear model works well in predicting structural load capacity, but significantly differs from experimental results when predicting the global load-displacement response. For multi-scale non-linear model, both the failure mode and the load-displacement curve fit well with the experimental results.
2017, 34(4): 795-800.
doi: 10.13801/j.cnki.fhclxb.20160711.001
Abstract:
The formula of hybrid effect coefficient for the fracture strain of glass fiber/carbon fiber (GF/CF) inter-ply hybrid composite laminates was improved with better dispersity formula. Based on the formula of hybrid effect coefficient and the mixing rule, the prediction method on the tensile strength of unidirectional inter-ply hybrid composite laminates was put forward. The progressive damage FEM of the tensile strength of multidirectional composite laminates was established, into which the formula of hybrid effect coefficient and the improvement of tensile strength of low-elongation fiber lamina were introduced. On this basis, the prediction method of the tensile strength of multidirectional inter-ply hybrid composite laminates was proposed. In the model, the stiffness degradation cases of progressive damage were also discussed. The results show that the computational results are well consistent with the test results as a whole, especially better for the computational results with considering hybrid effect. The larger stiffness degradation coefficient of matrix shows better results.
The formula of hybrid effect coefficient for the fracture strain of glass fiber/carbon fiber (GF/CF) inter-ply hybrid composite laminates was improved with better dispersity formula. Based on the formula of hybrid effect coefficient and the mixing rule, the prediction method on the tensile strength of unidirectional inter-ply hybrid composite laminates was put forward. The progressive damage FEM of the tensile strength of multidirectional composite laminates was established, into which the formula of hybrid effect coefficient and the improvement of tensile strength of low-elongation fiber lamina were introduced. On this basis, the prediction method of the tensile strength of multidirectional inter-ply hybrid composite laminates was proposed. In the model, the stiffness degradation cases of progressive damage were also discussed. The results show that the computational results are well consistent with the test results as a whole, especially better for the computational results with considering hybrid effect. The larger stiffness degradation coefficient of matrix shows better results.
2017, 34(4): 801-811.
doi: 10.13801/j.cnki.fhclxb.20160706.001
Abstract:
A new micro failure criteria based on the physical failure mechanism was proposed from the standpoint of micro-mechanics. The criteria follows Mohr-Coulomb criteria, in which damage type and failure mechanism under compressive load was emphasized. This study argued that shear damage will be prevented by compressive stress on the fracture surface. Fiber compressive failure mode was also researched in depth. A concept of shear strength on fiber kinking surface was introduced in fiber kinking failure criteria. Failure prediction and quantitative evaluation for lamina in the Second World Wide Failure Exercise were carried out. The prediction results were compared with Puck, Pinho, Cuntze, Carrere, Tsai-Ha, Hansen and Huang criteria. Assessment results show that the criteria proposed in this study ranks first under tri-axial load. The effect on the strength of matrix by hydrostatic pressure was researched. The results show that influence factor is only relevant with fracture angle of matrix under single compressive load. The important divergence that whether the failure envelope is "open" or "closed" among each strength criteria in WWFEII was analyzed and discussed. This study suggests that there is no universally accurate answer, because it is connected with fiber volume fraction, mechanical properties, hydrostatic pressure and fracture angle of matrix under single compressive load.
A new micro failure criteria based on the physical failure mechanism was proposed from the standpoint of micro-mechanics. The criteria follows Mohr-Coulomb criteria, in which damage type and failure mechanism under compressive load was emphasized. This study argued that shear damage will be prevented by compressive stress on the fracture surface. Fiber compressive failure mode was also researched in depth. A concept of shear strength on fiber kinking surface was introduced in fiber kinking failure criteria. Failure prediction and quantitative evaluation for lamina in the Second World Wide Failure Exercise were carried out. The prediction results were compared with Puck, Pinho, Cuntze, Carrere, Tsai-Ha, Hansen and Huang criteria. Assessment results show that the criteria proposed in this study ranks first under tri-axial load. The effect on the strength of matrix by hydrostatic pressure was researched. The results show that influence factor is only relevant with fracture angle of matrix under single compressive load. The important divergence that whether the failure envelope is "open" or "closed" among each strength criteria in WWFEII was analyzed and discussed. This study suggests that there is no universally accurate answer, because it is connected with fiber volume fraction, mechanical properties, hydrostatic pressure and fracture angle of matrix under single compressive load.
2017, 34(4): 812-818.
doi: 10.13801/j.cnki.fhclxb.20160802.001
Abstract:
The melt flow properties and injection molding process of carbon fiber reinforced nylon 66 (CF/PA66) composites granules with different fiber mass fraction were analyzed and simulated respectively by capillary rheometer and homemade small molds. The parameters of CF/PA66 injection molding process were quickly obtained. The results show that the melt of CF/PA66 composites belongs to the power-law fluid, and the melt viscosity changes significantly with temperature, pressure and the carbon fiber mass fraction, the melt rheological properties change from pseudo-plastic area into Newton area while the temperature and pressure go up to the critical value. With the increase of the carbon fiber mass fraction, the suitable molding temperature of CF/PA66 improves, that of PA66, PA66 with 10wt% and 20wt% CF in our experiments are 278-285℃, 280-287℃ and 290-298℃, respectively. By means of Bagley pressure correction to the melt, the smallest injection pressure of three granules suitable for forming are 24.3 MPa, 29.4 MPa, 35.1 MPa, respectively. These parameters from rheometer simulation are applied to injection molding process, it is found that the tensile strength of samples prepared by rheometer is quite close to the samples by injection molding, which will further prove that the capillary rheometer simulation of CF/PA66 injection molding process is feasible and effective, and provid the theory basis to determine the injection molding.
The melt flow properties and injection molding process of carbon fiber reinforced nylon 66 (CF/PA66) composites granules with different fiber mass fraction were analyzed and simulated respectively by capillary rheometer and homemade small molds. The parameters of CF/PA66 injection molding process were quickly obtained. The results show that the melt of CF/PA66 composites belongs to the power-law fluid, and the melt viscosity changes significantly with temperature, pressure and the carbon fiber mass fraction, the melt rheological properties change from pseudo-plastic area into Newton area while the temperature and pressure go up to the critical value. With the increase of the carbon fiber mass fraction, the suitable molding temperature of CF/PA66 improves, that of PA66, PA66 with 10wt% and 20wt% CF in our experiments are 278-285℃, 280-287℃ and 290-298℃, respectively. By means of Bagley pressure correction to the melt, the smallest injection pressure of three granules suitable for forming are 24.3 MPa, 29.4 MPa, 35.1 MPa, respectively. These parameters from rheometer simulation are applied to injection molding process, it is found that the tensile strength of samples prepared by rheometer is quite close to the samples by injection molding, which will further prove that the capillary rheometer simulation of CF/PA66 injection molding process is feasible and effective, and provid the theory basis to determine the injection molding.
2017, 34(4): 819-826.
doi: 10.13801/j.cnki.fhclxb.20160712.001
Abstract:
The shell elements with different section parameters and the solid elements with different equivalent material properties were used in the finite elements analysis of the composite marine propeller blade. The modal analysis, the response under uniformly distributed pressure loads and the thermal deformation in uniformly distributed temperature fields of the shell finite element modeling (FEM) were compared with those of the solid FEM. The results show that each of the two modeling methods has its own advantages and disadvantages on the modeling time and the layup adjusting convenience for blade with a variable layup from root to tip. There are some differences in the frequencies and the mode shapes in the modal analysis between two different FEMs, and each FEM is practicable for the modal analysis of the composite propeller blade under a given condition. For the two models, the shell FEM should be used in the response simulation under uniformly distributed pressure loads, while the solid FEM is suggested to analyze the thermal deformation of the blade in uniformly distributed temperature fields.
The shell elements with different section parameters and the solid elements with different equivalent material properties were used in the finite elements analysis of the composite marine propeller blade. The modal analysis, the response under uniformly distributed pressure loads and the thermal deformation in uniformly distributed temperature fields of the shell finite element modeling (FEM) were compared with those of the solid FEM. The results show that each of the two modeling methods has its own advantages and disadvantages on the modeling time and the layup adjusting convenience for blade with a variable layup from root to tip. There are some differences in the frequencies and the mode shapes in the modal analysis between two different FEMs, and each FEM is practicable for the modal analysis of the composite propeller blade under a given condition. For the two models, the shell FEM should be used in the response simulation under uniformly distributed pressure loads, while the solid FEM is suggested to analyze the thermal deformation of the blade in uniformly distributed temperature fields.
2017, 34(4): 827-835.
doi: 10.13801/j.cnki.fhclxb.20160715.001
Abstract:
Silicon carbide particle (SiCP) preforms with the particles sizes of 20 μm, 50 μm, 100 μm and 150 μm were prepared by compression mold forming and sinter process. High resolution (~1.0 μm) 3D X-ray micro-computed tomography combined with 3D pore-network models was used to study the effect of SiCP particle size on the 3D morphologies and spatial structures of pores in the SiCP preforms. The results show that the increase of the SiCP particle size reduces the gap expansions caused by the starch decomposition and enlarges the interval voids among the packed particles. As the SiCP particle size increasing from 20 μm to 100 μm, the pore shapes in the preform sections become more irregular, and hence the average area porosity of pores decreases as well as the spatial volume distribution homogeneity and the connectivity of pores become worse. In the pore-networks, the average effective sizes of both pores and throats increases, whereas the number of small pores or throats and the average pore coordination number decrease. When the SiCP particle size reaches up to 150 μm, the larger gaps can be filled by more small particles and the pore spaces are segmented by the residual netlike binders on the particles surface, so that the spatial distribution homogeneity of pore volumes and the connectivity decrease significantly. Therefore in the pore-networks, the number of small pores or throats and the average pore coordination number increase.
Silicon carbide particle (SiCP) preforms with the particles sizes of 20 μm, 50 μm, 100 μm and 150 μm were prepared by compression mold forming and sinter process. High resolution (~1.0 μm) 3D X-ray micro-computed tomography combined with 3D pore-network models was used to study the effect of SiCP particle size on the 3D morphologies and spatial structures of pores in the SiCP preforms. The results show that the increase of the SiCP particle size reduces the gap expansions caused by the starch decomposition and enlarges the interval voids among the packed particles. As the SiCP particle size increasing from 20 μm to 100 μm, the pore shapes in the preform sections become more irregular, and hence the average area porosity of pores decreases as well as the spatial volume distribution homogeneity and the connectivity of pores become worse. In the pore-networks, the average effective sizes of both pores and throats increases, whereas the number of small pores or throats and the average pore coordination number decrease. When the SiCP particle size reaches up to 150 μm, the larger gaps can be filled by more small particles and the pore spaces are segmented by the residual netlike binders on the particles surface, so that the spatial distribution homogeneity of pore volumes and the connectivity decrease significantly. Therefore in the pore-networks, the number of small pores or throats and the average pore coordination number increase.
2017, 34(4): 836-843.
doi: 10.13801/j.cnki.fhclxb.20160927.001
Abstract:
The effect of Si coated on the graphite surface and the grain diameter of graphite flake on thermal and mechanical properties of graphite/Al composites was researched. The results show that the SiC layer is formed during coating process, which is beneficial to suppress the formation of Al4C3 phase and enhance the interface bonding. The thermal conductivity in X-Y plane direction of the graphite-Si/Al composite increases from 492 W/(m·K) to 654 W/(m·K) as the volume fraction of the graphite increases from 50vol% to 70vol%. The flexure strength of graphite/Al composites with 50vol% graphite approachs 81 MPa, which increases by 53% than that of the uncoated graphite/Al. The thermal conductivity in X-Y plane direction of graphite-Si/Al composite decreases from 654 W/(m·K) to 445 W/(m·K) with the grain diameter of the graphite decreases from 500 μm to 150 μm. However, the thermal conductivity in Z plane direction and the flexure strength exhibit no significant change.
The effect of Si coated on the graphite surface and the grain diameter of graphite flake on thermal and mechanical properties of graphite/Al composites was researched. The results show that the SiC layer is formed during coating process, which is beneficial to suppress the formation of Al4C3 phase and enhance the interface bonding. The thermal conductivity in X-Y plane direction of the graphite-Si/Al composite increases from 492 W/(m·K) to 654 W/(m·K) as the volume fraction of the graphite increases from 50vol% to 70vol%. The flexure strength of graphite/Al composites with 50vol% graphite approachs 81 MPa, which increases by 53% than that of the uncoated graphite/Al. The thermal conductivity in X-Y plane direction of graphite-Si/Al composite decreases from 654 W/(m·K) to 445 W/(m·K) with the grain diameter of the graphite decreases from 500 μm to 150 μm. However, the thermal conductivity in Z plane direction and the flexure strength exhibit no significant change.
2017, 34(4): 844-849.
doi: 10.13801/j.cnki.fhclxb.20160607.004
Abstract:
The BaTiO3@Cu core-shell composite particles were prepared by simple one-step method using BaTiO3 microspheres with an average size about 500 nm as based shell. The structure, component, morphology, surface chemical elements, dielectric and magnetic properties of the BaTiO3@Cu core-shell composite particles were characterized by SEM, TEM, XPS, dielectric analyzer and impedance analyzer. The BaTiO3 and BaTiO3@Cu particles were dispersed into gelatin hydrogel elastomers cured with/without an electric, magnetic or electromagnetic field in order to measure the storage modulus of the elastomers and investigate the electro, magneto and electromagnetic response properties of the particles in the gelatin hydrogel elastomers. The results show that the composite particles present excellent core-shell structure with good electro and magneto response. On the surface of the composite particles, the Cu(0) accounts for about 90at% of the total Cu element. It is indicated that BaTiO3@Cu core-shell composite particle is a new type of multifunctional smart material responding to applied electric and magnetic field, and compared with the bare BaTiO3 particles, the electromagnetic response performance of the BaTiO3@Cu composite particles is obviously improved.
The BaTiO3@Cu core-shell composite particles were prepared by simple one-step method using BaTiO3 microspheres with an average size about 500 nm as based shell. The structure, component, morphology, surface chemical elements, dielectric and magnetic properties of the BaTiO3@Cu core-shell composite particles were characterized by SEM, TEM, XPS, dielectric analyzer and impedance analyzer. The BaTiO3 and BaTiO3@Cu particles were dispersed into gelatin hydrogel elastomers cured with/without an electric, magnetic or electromagnetic field in order to measure the storage modulus of the elastomers and investigate the electro, magneto and electromagnetic response properties of the particles in the gelatin hydrogel elastomers. The results show that the composite particles present excellent core-shell structure with good electro and magneto response. On the surface of the composite particles, the Cu(0) accounts for about 90at% of the total Cu element. It is indicated that BaTiO3@Cu core-shell composite particle is a new type of multifunctional smart material responding to applied electric and magnetic field, and compared with the bare BaTiO3 particles, the electromagnetic response performance of the BaTiO3@Cu composite particles is obviously improved.
2017, 34(4): 850-858.
doi: 10.13801/j.cnki.fhclxb.20170122.001
Abstract:
In this paper, the heat transfer mechanism of micro-truss sandwich panel with channels was investi-gated. Based on some conservative assumptions, a simple and effective model for evaluating the thermal insulant performance of the sandwich panel was proposed. Meanwhile, a rapid method for evaluating the thermal insulant performance of the new integrative thermal protection structure with active cooling was established. The effectiveness and validity of this analysis model were verified by comparing with the detailed numerical simulation results provided by Fluent software. This study offers a support for the further application of the new structure.
In this paper, the heat transfer mechanism of micro-truss sandwich panel with channels was investi-gated. Based on some conservative assumptions, a simple and effective model for evaluating the thermal insulant performance of the sandwich panel was proposed. Meanwhile, a rapid method for evaluating the thermal insulant performance of the new integrative thermal protection structure with active cooling was established. The effectiveness and validity of this analysis model were verified by comparing with the detailed numerical simulation results provided by Fluent software. This study offers a support for the further application of the new structure.
2017, 34(4): 859-864.
doi: 10.13801/j.cnki.fhclxb.20160612.003
Abstract:
ZnAl2O4 and La3+ (from La2O3) doped Ca0.61Nd0.26TiO3-MgTiO3 powders were synthesized by solid-state reaction method, which were used for preparing ZnAl2O4 and La3+ doped Ca0.61Nd0.26TiO3-MgTiO3 composite ceramics through dry-pressing and sintering in air atmosphere. The effects of doping contents of La3+ and ZnAl2O4 on the microstructure, phase formation and dielectric properties performance of the composite ceramics were investigated. The results show that ZnAl2O4 additive can adjust the crystallite size, so the density of the sintered ceramics increases with the increase of La3+ and ZnAl2O4 contents. The dielectric constant and temperature coefficient of the composite ceramics decrease with the increase of ZnAl2O4 content, but are not significantly affected by the La3+ content. The quality factor of the composite ceramics increases first and then decrease with the increase of ZnAl2O4 content. The obtained composite ceramics with a sintered density above 94% displays good dielectric properties, such as dielectric constant is about 40-50, temperature coefficient is less than 40×10-6℃-1 and quality factor is larger than 38 000 GHz. Thus ZnAl2O4 and La3+ doped Ca0.61Nd0.26TiO3-MgTiO3 composite ceramics can be used in the field of communication technology.
ZnAl2O4 and La3+ (from La2O3) doped Ca0.61Nd0.26TiO3-MgTiO3 powders were synthesized by solid-state reaction method, which were used for preparing ZnAl2O4 and La3+ doped Ca0.61Nd0.26TiO3-MgTiO3 composite ceramics through dry-pressing and sintering in air atmosphere. The effects of doping contents of La3+ and ZnAl2O4 on the microstructure, phase formation and dielectric properties performance of the composite ceramics were investigated. The results show that ZnAl2O4 additive can adjust the crystallite size, so the density of the sintered ceramics increases with the increase of La3+ and ZnAl2O4 contents. The dielectric constant and temperature coefficient of the composite ceramics decrease with the increase of ZnAl2O4 content, but are not significantly affected by the La3+ content. The quality factor of the composite ceramics increases first and then decrease with the increase of ZnAl2O4 content. The obtained composite ceramics with a sintered density above 94% displays good dielectric properties, such as dielectric constant is about 40-50, temperature coefficient is less than 40×10-6℃-1 and quality factor is larger than 38 000 GHz. Thus ZnAl2O4 and La3+ doped Ca0.61Nd0.26TiO3-MgTiO3 composite ceramics can be used in the field of communication technology.
2017, 34(4): 865-872.
doi: 10.13801/j.cnki.fhclxb.20160720.001
Abstract:
In order to analyze the influence of fiber length on the bending strength and breathability of the ceramic fiber reinforced silica sol shell, the ceramic fibers with six different lengths from 1 mm to 6 mm were added to the silica sol slurry to reinforce shell. The results show that the length of the ceramic fiber has a significant effect on the strength and breathability of silica sol shell. With the increase of the ceramic fiber length, the bending strength of the shell increases first and then decreases, and the breathability of the shell increases first, then decreases and increases again. When the fiber length is 4 mm, the green strength and fired strength of the shell reach the maximum about 2.97 MPa and 6.84 MPa, respectively, and the breathability of the shell also reaches the maximum about 2.90. When the fiber length is more than 4 mm, the dispersion of fiber in shell gets worse, and the influence of fiber bridging is not obviously effective. The porosity of the shell reduces, which leads to the decrease of the strength and breathability of the shell.
In order to analyze the influence of fiber length on the bending strength and breathability of the ceramic fiber reinforced silica sol shell, the ceramic fibers with six different lengths from 1 mm to 6 mm were added to the silica sol slurry to reinforce shell. The results show that the length of the ceramic fiber has a significant effect on the strength and breathability of silica sol shell. With the increase of the ceramic fiber length, the bending strength of the shell increases first and then decreases, and the breathability of the shell increases first, then decreases and increases again. When the fiber length is 4 mm, the green strength and fired strength of the shell reach the maximum about 2.97 MPa and 6.84 MPa, respectively, and the breathability of the shell also reaches the maximum about 2.90. When the fiber length is more than 4 mm, the dispersion of fiber in shell gets worse, and the influence of fiber bridging is not obviously effective. The porosity of the shell reduces, which leads to the decrease of the strength and breathability of the shell.
2017, 34(4): 873-880.
doi: 10.13801/j.cnki.fhclxb.20160905.001
Abstract:
In order to improve the cycle performance of lithium sulfur battery, the multiwalled carbon nanotubes (MWCNTs) paper were prepared by vacuum filtration method using paper fibers as the matrix and MWCNTs as the conductive additive. The MWCNTs paper was applied as the cathode current collector for lithium sulfur battery instead of aluminum foil. The morphology structure were characterized by SEM and the electrochemical properties were tested by the cell tester, and the EDS element analysis for the MWCNTs paper and sulfur composite cathode after cycles were also performed. The results show that MWCNTs are uniformly adhered to the paper fiber, and the porous MWCNTs paper has obviously 3D structure. The electrochemical tests indicate that the lithium sulfur battery with MWCNTs paper as current collector hold a specific capacity of 615 mAh/g and 496 mAh/g after 30 cycles in the current rate of 0.05 C and 1 C, respectively. The Coulombic efficiency maintains as high as 97.5%, and the charge transfer resistance decrease after cycles. The EDS element analysis verifies that the MWCNTs paper has adsorption role for the lithium polysulfides. The shuttle effect is restrained in some degree by the MWCNTs paper. As a result, MWCNTs paper used as the current collector can increase the sulfur loading capacity and contact area significantly, and improve the cycle stability and the Coulombic efficiency of lithium-sulfur battery.
In order to improve the cycle performance of lithium sulfur battery, the multiwalled carbon nanotubes (MWCNTs) paper were prepared by vacuum filtration method using paper fibers as the matrix and MWCNTs as the conductive additive. The MWCNTs paper was applied as the cathode current collector for lithium sulfur battery instead of aluminum foil. The morphology structure were characterized by SEM and the electrochemical properties were tested by the cell tester, and the EDS element analysis for the MWCNTs paper and sulfur composite cathode after cycles were also performed. The results show that MWCNTs are uniformly adhered to the paper fiber, and the porous MWCNTs paper has obviously 3D structure. The electrochemical tests indicate that the lithium sulfur battery with MWCNTs paper as current collector hold a specific capacity of 615 mAh/g and 496 mAh/g after 30 cycles in the current rate of 0.05 C and 1 C, respectively. The Coulombic efficiency maintains as high as 97.5%, and the charge transfer resistance decrease after cycles. The EDS element analysis verifies that the MWCNTs paper has adsorption role for the lithium polysulfides. The shuttle effect is restrained in some degree by the MWCNTs paper. As a result, MWCNTs paper used as the current collector can increase the sulfur loading capacity and contact area significantly, and improve the cycle stability and the Coulombic efficiency of lithium-sulfur battery.
2017, 34(4): 881-889.
doi: 10.13801/j.cnki.fhclxb.20160906.002
Abstract:
Based on the theory of bionics, nano β-tricalcium phosphate-collagen/chondroitin sulfate (nano β-TCP-Col/CS) scaffold composites were modified by dehydrathermal (DHT) and 1-Ethyl-3-(3-Dimethylaminopropyl) (EDC) using nano β-tricalcium phosphate(nano β-TCP), collagen(Col) and chondroitin sulfate(CS) as the raw materials. The structure and properties of nano β-TCP-Col/CS scaffold composites were investigated by XRD, AFM, SEM, XPS, TG and degradation and mineralization in simulated body fluid (SBF). The results indicate that the size of β-TCP is 41.3nm. Due to a strong interaction among nano β-TCP, Col and CS, nano β-TCP-Col/CS scaffold composites has strong stability, mineralized biological activity and appropriate biodegradability, which is a kind of potential dental restorative materials.
Based on the theory of bionics, nano β-tricalcium phosphate-collagen/chondroitin sulfate (nano β-TCP-Col/CS) scaffold composites were modified by dehydrathermal (DHT) and 1-Ethyl-3-(3-Dimethylaminopropyl) (EDC) using nano β-tricalcium phosphate(nano β-TCP), collagen(Col) and chondroitin sulfate(CS) as the raw materials. The structure and properties of nano β-TCP-Col/CS scaffold composites were investigated by XRD, AFM, SEM, XPS, TG and degradation and mineralization in simulated body fluid (SBF). The results indicate that the size of β-TCP is 41.3nm. Due to a strong interaction among nano β-TCP, Col and CS, nano β-TCP-Col/CS scaffold composites has strong stability, mineralized biological activity and appropriate biodegradability, which is a kind of potential dental restorative materials.
2017, 34(4): 890-898.
doi: 10.13801/j.cnki.fhclxb.20161205.002
Abstract:
Magnetic activate carbon (MAC) coupled by chitosan-glutaraldehyde crosslinking technique was synthesized by ferric salts chemical precipitation method using activate carbon as raw meterial. Based on MAC, Br-N codoped TiO2/magnetic carbon composites (Brx-N-TiO2/MAC) were prepared by a facile sol-gel method.The synthesized composites were characterized by XRD, UV-Vis diffuse reflectance spectroscopy (DRS), N2 adsorption-desorption test (BET), SEM and XPS. The photocatalytic activity of the composites was evaluated by photocatalytic degradation of salicylic acid under visible light irradiation. Compared with N-TiO2/MAC, Brx-N-TiO2/MAC has a better photocatalytic performance. The degradation effect of Br0.35-N-TiO2/MAC to salicylic acid is the best, and the photocatalytic degradation rate of Br0.35-N-TiO2/MAC for 3 h can reach up to 83% after 1 h dark absorption. High concentration of salicylic acid can inhibit the photocatalytic reaction rate of Brx-N-TiO2/MAC. After reused for three times, the removal rate of Br0.35-N-TiO2/MAC to salicylic acid can still reach 78%, which proves the composites have a good chemical stability.
Magnetic activate carbon (MAC) coupled by chitosan-glutaraldehyde crosslinking technique was synthesized by ferric salts chemical precipitation method using activate carbon as raw meterial. Based on MAC, Br-N codoped TiO2/magnetic carbon composites (Brx-N-TiO2/MAC) were prepared by a facile sol-gel method.The synthesized composites were characterized by XRD, UV-Vis diffuse reflectance spectroscopy (DRS), N2 adsorption-desorption test (BET), SEM and XPS. The photocatalytic activity of the composites was evaluated by photocatalytic degradation of salicylic acid under visible light irradiation. Compared with N-TiO2/MAC, Brx-N-TiO2/MAC has a better photocatalytic performance. The degradation effect of Br0.35-N-TiO2/MAC to salicylic acid is the best, and the photocatalytic degradation rate of Br0.35-N-TiO2/MAC for 3 h can reach up to 83% after 1 h dark absorption. High concentration of salicylic acid can inhibit the photocatalytic reaction rate of Brx-N-TiO2/MAC. After reused for three times, the removal rate of Br0.35-N-TiO2/MAC to salicylic acid can still reach 78%, which proves the composites have a good chemical stability.
2017, 34(4): 899-905.
doi: 10.13801/j.cnki.fhclxb.20160920.002
Abstract:
In order to improve the usability of starch/polyvinyl alcohol (PVA) composite film in the application based on the films such as warp sizing in textile, the preparation of quaternized-maleated cornstarch (QMS) was performed by a method of two-step reaction. In terms of the tensile strength, the breaking elongation, the flex fatigue resistance, and the toughening law of modification level (the sum of quaternization level and maleation one) on QMS/PVA composite films was explored, and the effect of mass ratio of PVA to QMS on the toughness of QMS/PVA composite films was also investigated. It can be found that the tensile strength of QMS/PVA composite films reduces from 21.6 MPa to 14.8 MPa, and the breaking elongation and the number of bending of QMS/PVA composite film increase from 26.6% to 29.5% and from 4 348 cycles to 5 388 cycles when the modification level of QMS is 0.061. When the mass ratios of PVA to QMS changes from 0 to 100%, the elongation of QMS/PVA composite films rises from 3.35% to 43.9%, the number of bending increases from 2 128 cycles to 7889 cycles, and the strength decreases from 27.1 MPa to 12.1 MPa. These results suggest that the mass ratio is the index of actors that influences the toughness of QMS/PVA composite films. The suitable mass ratio is about 66.7% based on the film properties.
In order to improve the usability of starch/polyvinyl alcohol (PVA) composite film in the application based on the films such as warp sizing in textile, the preparation of quaternized-maleated cornstarch (QMS) was performed by a method of two-step reaction. In terms of the tensile strength, the breaking elongation, the flex fatigue resistance, and the toughening law of modification level (the sum of quaternization level and maleation one) on QMS/PVA composite films was explored, and the effect of mass ratio of PVA to QMS on the toughness of QMS/PVA composite films was also investigated. It can be found that the tensile strength of QMS/PVA composite films reduces from 21.6 MPa to 14.8 MPa, and the breaking elongation and the number of bending of QMS/PVA composite film increase from 26.6% to 29.5% and from 4 348 cycles to 5 388 cycles when the modification level of QMS is 0.061. When the mass ratios of PVA to QMS changes from 0 to 100%, the elongation of QMS/PVA composite films rises from 3.35% to 43.9%, the number of bending increases from 2 128 cycles to 7889 cycles, and the strength decreases from 27.1 MPa to 12.1 MPa. These results suggest that the mass ratio is the index of actors that influences the toughness of QMS/PVA composite films. The suitable mass ratio is about 66.7% based on the film properties.
2017, 34(4): 906-914.
doi: 10.13801/j.cnki.fhclxb.20160616.004
Abstract:
The microstructure and the high-and-low temperature performance of matrix asphalt and styrene-butadiene-styrene tri-block copolymer(SBS) modified asphalt before and after the salt freezing cycle were studied by the AFM, DSR and BBR, respectively. The results indicate that the asphaltene content of matrix asphalt increases and the dispersion situation of matrix asphalt gets worse, and three-dimensional network structure of SBS modifier is destroyed due to the number and size of asphalt "bee" structures changing after freeze-thaw cycles. The high temperature performance of matrix asphalt increases slightly and anti-fatigue performance decreases after the salt freezing cycle, while high temperature property of SBS modified asphalt decreases and the fatigue properties increases. To a certain degree, the increase of salt concentration make the low temperature cracking resistance of matrix asphalt reduce. However, when the concentration of salt reaches up to 4wt%, the low temperature cracking resistance of SBS modified asphalt is improved. Hence, the high-and-low temperature performance of SBS modified asphalt is better than that of matrix asphalt. It is recommended that SBS modified asphalt should be chose as the pavement material in the cold region as far as possible.
The microstructure and the high-and-low temperature performance of matrix asphalt and styrene-butadiene-styrene tri-block copolymer(SBS) modified asphalt before and after the salt freezing cycle were studied by the AFM, DSR and BBR, respectively. The results indicate that the asphaltene content of matrix asphalt increases and the dispersion situation of matrix asphalt gets worse, and three-dimensional network structure of SBS modifier is destroyed due to the number and size of asphalt "bee" structures changing after freeze-thaw cycles. The high temperature performance of matrix asphalt increases slightly and anti-fatigue performance decreases after the salt freezing cycle, while high temperature property of SBS modified asphalt decreases and the fatigue properties increases. To a certain degree, the increase of salt concentration make the low temperature cracking resistance of matrix asphalt reduce. However, when the concentration of salt reaches up to 4wt%, the low temperature cracking resistance of SBS modified asphalt is improved. Hence, the high-and-low temperature performance of SBS modified asphalt is better than that of matrix asphalt. It is recommended that SBS modified asphalt should be chose as the pavement material in the cold region as far as possible.
2017, 34(4): 915-921.
doi: 10.13801/j.cnki.fhclxb.20160713.001
Abstract:
By means of accelerated loading test, low temperature bending test and Cantabro test, the influences of two binder materials, including foamed asphalt and cement, on the high temperature deformation resistance, low temperature crack resistance and raveling resistance of cold recycled mixtures stabilized with foamed asphalt (CRMFA) were studied. The results indicate that there exists an optimum dosage of foamed asphalt to acquire good high temperature deformation resistance of CRMFA. The increase of cement content is conducive to boosting the high temperature deformation resistance of CRMFA. The low temperature flexibility of CRMFA increases with the increase of foamed asphalt content, but assumes parabolic relationship with the increase of cement content. To insure the favorable low temperature crack resistance, the dosage of cement is recommended to be less than 2wt%. The raveling resistance of CRMFA is poor and the increase of foamed asphalt content helps to effectively reduce the raveling resistance of CRMFA. The improvement of raveling resistance for CRMFA becomes non-significant while the addition content of cement increases to 1.5wt%-2.5wt%.
By means of accelerated loading test, low temperature bending test and Cantabro test, the influences of two binder materials, including foamed asphalt and cement, on the high temperature deformation resistance, low temperature crack resistance and raveling resistance of cold recycled mixtures stabilized with foamed asphalt (CRMFA) were studied. The results indicate that there exists an optimum dosage of foamed asphalt to acquire good high temperature deformation resistance of CRMFA. The increase of cement content is conducive to boosting the high temperature deformation resistance of CRMFA. The low temperature flexibility of CRMFA increases with the increase of foamed asphalt content, but assumes parabolic relationship with the increase of cement content. To insure the favorable low temperature crack resistance, the dosage of cement is recommended to be less than 2wt%. The raveling resistance of CRMFA is poor and the increase of foamed asphalt content helps to effectively reduce the raveling resistance of CRMFA. The improvement of raveling resistance for CRMFA becomes non-significant while the addition content of cement increases to 1.5wt%-2.5wt%.
2017, 34(4): 922-931.
doi: 10.13801/j.cnki.fhclxb.20160906.001
Abstract:
Two kinds of water-based phosphorus flame retardants, DAG-50 and DAG-80, and their compound flame retardants were applied to modify the natural jute fibers. A novel type of jute fiber/polyester fiber composites was prepared by the hot-press method using the flame retarded jute fibers and polyester fibers with skin-core structure as raw material. The flame retarded effects and mechanism of these flame retardants were studied by combustion tests, SEM, FTIR, TGA and TGA-FTIR. Meanwhile, the flame retardant formula which is suitable for the industrialization of the jute fiber/polyester fiber composites was also screened out. The results show that DAG-50 presents good flame retardancy, but easily precipitates out on the surface of jute fibers. DAG-80 can coat uniformly on the surface of jute fibers with better flame retardancy, but it has much higher price than DAG-50. The compound flame retardant prepared by DAG-50 and DAG-80 shows excellent flame retardancy towards jute fibers. It is nearly neutral and can avoid the corrosion of equipment and overcome the problem of precipitating out when using DAG-50 alone. Considering cost and flame retardancy, the 55wt% compound flame retardant made up of DAG-50 and DAG-80 with the ratio of 2:1 can achieve flame retardant composites with B1 rank.
Two kinds of water-based phosphorus flame retardants, DAG-50 and DAG-80, and their compound flame retardants were applied to modify the natural jute fibers. A novel type of jute fiber/polyester fiber composites was prepared by the hot-press method using the flame retarded jute fibers and polyester fibers with skin-core structure as raw material. The flame retarded effects and mechanism of these flame retardants were studied by combustion tests, SEM, FTIR, TGA and TGA-FTIR. Meanwhile, the flame retardant formula which is suitable for the industrialization of the jute fiber/polyester fiber composites was also screened out. The results show that DAG-50 presents good flame retardancy, but easily precipitates out on the surface of jute fibers. DAG-80 can coat uniformly on the surface of jute fibers with better flame retardancy, but it has much higher price than DAG-50. The compound flame retardant prepared by DAG-50 and DAG-80 shows excellent flame retardancy towards jute fibers. It is nearly neutral and can avoid the corrosion of equipment and overcome the problem of precipitating out when using DAG-50 alone. Considering cost and flame retardancy, the 55wt% compound flame retardant made up of DAG-50 and DAG-80 with the ratio of 2:1 can achieve flame retardant composites with B1 rank.
2017, 34(4): 932-938.
doi: 10.13801/j.cnki.fhclxb.20160822.001
Abstract:
According to the microstructure of the thick-wall fiber cells of wild oat awns, a mechanical model of filament-wounded anisotropic tubular body was established and the constitutive relation of the fibroblasts under humidity load was derived. The effects of the microfibril angle, cell wall thickness and humidity conditions on strain and stress distribution were also analyzed. The results show that the anisotropic expansion of the filament-wound structure during the moisture changing can cause axial elongation and circumferential torsion of the tubular body. By comparing the relationship between deformations and microfibril angle, it is found that the microfibril angle of the model with stable deformation is laid in the range of 60°-80°.
According to the microstructure of the thick-wall fiber cells of wild oat awns, a mechanical model of filament-wounded anisotropic tubular body was established and the constitutive relation of the fibroblasts under humidity load was derived. The effects of the microfibril angle, cell wall thickness and humidity conditions on strain and stress distribution were also analyzed. The results show that the anisotropic expansion of the filament-wound structure during the moisture changing can cause axial elongation and circumferential torsion of the tubular body. By comparing the relationship between deformations and microfibril angle, it is found that the microfibril angle of the model with stable deformation is laid in the range of 60°-80°.
