2018 Vol. 35, No. 3
2018, 35(3): 477-484.
doi: 10.13801/j.cnki.fhclxb.20170608.004
Abstract:
Polymethylmethacrylate (PMMA)/lithium ethylene-vinyl alcohol copolymer sulfate (EVOH-SO3Li) Li-ion battery separator composite was prepared by means of electrostatic spinning alternated, PMMA and EVOH-SO3Li as raw materials. The performance of PMMA/EVOH-SO3Li separator composite was characterized by FTIR, SEM, universal tensile tester, TGA, IM6 electrochemical workstation and battery cycler. The results show that PMMA/EVOH-SO3Li separator composite has a clear three-dimensional network structure. Compared with EVOH-SO3Li separator, the porosity, absorption rate and tensile strength of modified PMMA/EVOH-SO3Li separator composite are increased to 80%, 340% and 3.18 MPa, respectively. The initial thermal decomposition temperature is also rised to 294℃. The thermal shrinkage rate is reduced. The excellent electrochemical performance is exhibited. The electrochemical stability window is increased from 5.0 V to 5.6 V. The interfacial impedance is reduced from 420.69 Ω to 262.31 Ω. The ionic conductivity is increased from 1.560×10-3 S/cm to 2.089×10-3 S/cm. The coulombic efficiency is 93.7% after 100 cycles of charge and discharge.
Polymethylmethacrylate (PMMA)/lithium ethylene-vinyl alcohol copolymer sulfate (EVOH-SO3Li) Li-ion battery separator composite was prepared by means of electrostatic spinning alternated, PMMA and EVOH-SO3Li as raw materials. The performance of PMMA/EVOH-SO3Li separator composite was characterized by FTIR, SEM, universal tensile tester, TGA, IM6 electrochemical workstation and battery cycler. The results show that PMMA/EVOH-SO3Li separator composite has a clear three-dimensional network structure. Compared with EVOH-SO3Li separator, the porosity, absorption rate and tensile strength of modified PMMA/EVOH-SO3Li separator composite are increased to 80%, 340% and 3.18 MPa, respectively. The initial thermal decomposition temperature is also rised to 294℃. The thermal shrinkage rate is reduced. The excellent electrochemical performance is exhibited. The electrochemical stability window is increased from 5.0 V to 5.6 V. The interfacial impedance is reduced from 420.69 Ω to 262.31 Ω. The ionic conductivity is increased from 1.560×10-3 S/cm to 2.089×10-3 S/cm. The coulombic efficiency is 93.7% after 100 cycles of charge and discharge.
2018, 35(3): 485-492.
doi: 10.13801/j.cnki.fhclxb.20170601.006
Abstract:
A novel reactive flame retardant (DOPO-PHBA) was synthesized by the reaction between 9,10-dihydro-9-oxa-10-phosphine-10-oxide (DOPO) and p-hydroxybenzaldehyde (PHBA).Its structure and composition were characterized by FTIR and nuclear magnetic resonance spectroscopy 1H-NMR and 31P-NMR. DOPO-PHBA was compounded with triglycidyl isocyanurate (TGIC) to prepare DOPO-PHBA-TGIC/epoxy resin(EP) composites. The flame retardancy and thermal properties of DOPO-PHBA-TGIC/EP composites were respectively investigated by limiting oxygen index (LOI), dynamic mechanical analysis (DMA) and thermogravimetric analysis. Results indicate that DOPO-PHBA is successfully synthesized. The addition of DOPO-PHBA-TGIC can significantly enhance the flame retardancy of EP resin, while the mass fraction of phosphorus is 0.6wt%, LOI value increases from 24% to 32.5%. Additionally, the glass transition temperature (Tg) of DOPO-PHBA-TGIC/EP composites with different phosphorus mass fractions are maintained at 200℃ or higher, and the residues at 800℃ under nitrogen atmosphere are increased. But the initial degradation temperatures and maximum decomposition rates of DOPO-PHBA-TGIC/EP composites are decreased. FTIR analysis of char residues reveal that this flame retardant system satisfies condensed phase flame retardant mechanism, and the incorporation of DOPO-PHBA-TGIC does not impair the physical property of EP resin.
A novel reactive flame retardant (DOPO-PHBA) was synthesized by the reaction between 9,10-dihydro-9-oxa-10-phosphine-10-oxide (DOPO) and p-hydroxybenzaldehyde (PHBA).Its structure and composition were characterized by FTIR and nuclear magnetic resonance spectroscopy 1H-NMR and 31P-NMR. DOPO-PHBA was compounded with triglycidyl isocyanurate (TGIC) to prepare DOPO-PHBA-TGIC/epoxy resin(EP) composites. The flame retardancy and thermal properties of DOPO-PHBA-TGIC/EP composites were respectively investigated by limiting oxygen index (LOI), dynamic mechanical analysis (DMA) and thermogravimetric analysis. Results indicate that DOPO-PHBA is successfully synthesized. The addition of DOPO-PHBA-TGIC can significantly enhance the flame retardancy of EP resin, while the mass fraction of phosphorus is 0.6wt%, LOI value increases from 24% to 32.5%. Additionally, the glass transition temperature (Tg) of DOPO-PHBA-TGIC/EP composites with different phosphorus mass fractions are maintained at 200℃ or higher, and the residues at 800℃ under nitrogen atmosphere are increased. But the initial degradation temperatures and maximum decomposition rates of DOPO-PHBA-TGIC/EP composites are decreased. FTIR analysis of char residues reveal that this flame retardant system satisfies condensed phase flame retardant mechanism, and the incorporation of DOPO-PHBA-TGIC does not impair the physical property of EP resin.
2018, 35(3): 493-500.
doi: 10.13801/j.cnki.fhclxb.20170517.003
Abstract:
Laminated film compression-molding was used to fabricate nano Al2O3-carbon fiber multi-scale reinforced PA6 matrix (nano Al2O3-CFF/PA6) composite laminates. The effect of molding temperature, compression pressure and nano Al2O3 content on the properties of nano Al2O3-CFF/PA6 laminates were investigated by FESEM, thermogravimetric analysis/differential scanning calorimetry simultaneous thermal analyzer(TGA/DSC) and FTIR. The results show that the flexural strength, interlaminar shear strength, and parallel/vertical impact strength of the CFF/PA6 laminates reach 250.3 MPa, 87.6 MPa, 41.2 MPa and 9.6 MPa while they are fabricated at 230℃, 3 MPa holding 15 min. When the content of nano Al2O3 in the matrix reaches to 6wt%, the corresponding mechanical strength of nano Al2O3-CFF/PA6 laminated composite are 387.6 MPa, 35.7 MPa, 80.3 MPa and 25.6 MPa, respectively.
Laminated film compression-molding was used to fabricate nano Al2O3-carbon fiber multi-scale reinforced PA6 matrix (nano Al2O3-CFF/PA6) composite laminates. The effect of molding temperature, compression pressure and nano Al2O3 content on the properties of nano Al2O3-CFF/PA6 laminates were investigated by FESEM, thermogravimetric analysis/differential scanning calorimetry simultaneous thermal analyzer(TGA/DSC) and FTIR. The results show that the flexural strength, interlaminar shear strength, and parallel/vertical impact strength of the CFF/PA6 laminates reach 250.3 MPa, 87.6 MPa, 41.2 MPa and 9.6 MPa while they are fabricated at 230℃, 3 MPa holding 15 min. When the content of nano Al2O3 in the matrix reaches to 6wt%, the corresponding mechanical strength of nano Al2O3-CFF/PA6 laminated composite are 387.6 MPa, 35.7 MPa, 80.3 MPa and 25.6 MPa, respectively.
2018, 35(3): 501-507.
doi: 10.13801/j.cnki.fhclxb.20170509.004
Abstract:
The surface modification of nano SiO2 particles with γ-aminopropyl triethoxysilane(KH550) was carried out, The SiO2-wood fiber/polyvinyl chloride(PVC) composites were prepared by melt-mixing with wood fiber, PVC and other additives. The structure and properties of SiO2 particles and SiO2-wood fiber/PVC composites were tested and characterized by FTIR, SEM and STA.FTIR analysis shows that the surface of SiO2 particles bond KH550 characteristic organic functional group, KH550 successfully grafts to the surface of SiO2 particles. SEM analysis shows that the modified nano-SiO2 particles can be dispersed uniformly in the SiO2-wood fiber/PVC composites with a particle size of about 100 nm; After adding the modified SiO2 particles, the combination of wood fiber and PVC is more tight, the hole gap is reduced. When the mass ratio of nano SiO2 to wood flour mass is 10%, 8%, 10%, the mechanical property of the SiO2-wood fiber/PVC composites will reach the optimal state:elastic modulus, tensile-strength and impact-strength are 4.66 GPa, 31.12 MPa and 4.11 kJ/m2, increased by 50.29%, 28.91% and 16.65%, respectively.
The surface modification of nano SiO2 particles with γ-aminopropyl triethoxysilane(KH550) was carried out, The SiO2-wood fiber/polyvinyl chloride(PVC) composites were prepared by melt-mixing with wood fiber, PVC and other additives. The structure and properties of SiO2 particles and SiO2-wood fiber/PVC composites were tested and characterized by FTIR, SEM and STA.FTIR analysis shows that the surface of SiO2 particles bond KH550 characteristic organic functional group, KH550 successfully grafts to the surface of SiO2 particles. SEM analysis shows that the modified nano-SiO2 particles can be dispersed uniformly in the SiO2-wood fiber/PVC composites with a particle size of about 100 nm; After adding the modified SiO2 particles, the combination of wood fiber and PVC is more tight, the hole gap is reduced. When the mass ratio of nano SiO2 to wood flour mass is 10%, 8%, 10%, the mechanical property of the SiO2-wood fiber/PVC composites will reach the optimal state:elastic modulus, tensile-strength and impact-strength are 4.66 GPa, 31.12 MPa and 4.11 kJ/m2, increased by 50.29%, 28.91% and 16.65%, respectively.
2018, 35(3): 508-513.
doi: 10.13801/j.cnki.fhclxb.20170601.007
Abstract:
Three types of surface modifiers, i.e. phenyl trimethoxy silane modifier (PTMS), solution of rare earth modifier (RES) containing PTMS (PTMS-RES) and RES solution, were used for the surface treatment of the milled glass fiber. The effects of the different surface treatment conditions on the dielectric properties, coefficient of thermal expansion and heat conduction properties of milled glass fiber reinforced milled glass fiber/polytetrafluoroethylene (MGF/PTFE) composites were investigated in detail, and FTIR spectra of RES, unmodified and modified of MGF, and the fracture surfaces were analyzed by SEM. The experimental results show that the dielectric properties, coefficient of thermal expansion and heat conduction properties of the MGF/PTFE composites filled with modified milled glass fiber are improved, compared with that of the MGF/PTFE composite filled with unmodified milled glass fiber. The effect of milled glass fiber with RES is superior to PTMS due to the effects of rare earth specific electronic structure and has a strong attraction to the anion, PTMS-RES is superior to RES in improving the interface and promoting the interfacial adhesion between the milled glass fiber and PTFE due to the effects of rare earth with PTMS.
Three types of surface modifiers, i.e. phenyl trimethoxy silane modifier (PTMS), solution of rare earth modifier (RES) containing PTMS (PTMS-RES) and RES solution, were used for the surface treatment of the milled glass fiber. The effects of the different surface treatment conditions on the dielectric properties, coefficient of thermal expansion and heat conduction properties of milled glass fiber reinforced milled glass fiber/polytetrafluoroethylene (MGF/PTFE) composites were investigated in detail, and FTIR spectra of RES, unmodified and modified of MGF, and the fracture surfaces were analyzed by SEM. The experimental results show that the dielectric properties, coefficient of thermal expansion and heat conduction properties of the MGF/PTFE composites filled with modified milled glass fiber are improved, compared with that of the MGF/PTFE composite filled with unmodified milled glass fiber. The effect of milled glass fiber with RES is superior to PTMS due to the effects of rare earth specific electronic structure and has a strong attraction to the anion, PTMS-RES is superior to RES in improving the interface and promoting the interfacial adhesion between the milled glass fiber and PTFE due to the effects of rare earth with PTMS.
2018, 35(3): 514-520.
doi: 10.13801/j.cnki.fhclxb.20170602.002
Abstract:
The polymethyl methacrylate(PMMA)@polybutadiene(PB) core-shell structured nanoparticles toughened bisphenol A-cyanate(BADCy) resin was prepared. The mechanical property results show that the PMMA@PB/BADCy resin presents excellent toughness when 6wt% of PMMA@PB core-shell rubber is used. And the impact strength of the PMMA@PB/BADCy resin with 6wt% of PMMA@PB core-shell rubber is 14.32 kJ·m-2, increased by 83.6%. The thermal performances of toughened resin were investigated by DMA and TG-DTA as well. The results show that when 6wt% of PMMA@PB core-shell rubber is used, the glass transition temperature of the cured PMMA@PB/BADCy resin is 236.8℃ and the temperature of maximum degradation rate is 410.0℃. TEM images show that the PMMA@PB core-shell rubber has good dispersion in BADCy resin. SEM images show that the fracture surface of PMMA@PB core-shell rubber toughened BADCy resin exhibits typical toughness fracture. The rheological properties of the PMMA@PB/BADCy resin show that the PMMA@PB core-shell rubber has insignificant influence on the rheological properties of BADCy resin. The lowest viscosity of the PMMA@PB/BADCy resin is 0.79 Pa·s, which is the ideal viscosity to impregnate fiber for preparing prepreg. The dielectric properties at different frequencies show that the PMMA@PB core-shell rubber has little effect on the dielectric properties of toughened BADCy. When 6wt% PMMA@PB core-shell rubber is used, the dielectric constant is 3.0 and the dielectric loss is about 0.010. The PMMA@PB/BADCy resin system presents excellent performances and can be used as matrix of prepreg. It is suitable for the manufacture of low dielectric composites in aerospace.
The polymethyl methacrylate(PMMA)@polybutadiene(PB) core-shell structured nanoparticles toughened bisphenol A-cyanate(BADCy) resin was prepared. The mechanical property results show that the PMMA@PB/BADCy resin presents excellent toughness when 6wt% of PMMA@PB core-shell rubber is used. And the impact strength of the PMMA@PB/BADCy resin with 6wt% of PMMA@PB core-shell rubber is 14.32 kJ·m-2, increased by 83.6%. The thermal performances of toughened resin were investigated by DMA and TG-DTA as well. The results show that when 6wt% of PMMA@PB core-shell rubber is used, the glass transition temperature of the cured PMMA@PB/BADCy resin is 236.8℃ and the temperature of maximum degradation rate is 410.0℃. TEM images show that the PMMA@PB core-shell rubber has good dispersion in BADCy resin. SEM images show that the fracture surface of PMMA@PB core-shell rubber toughened BADCy resin exhibits typical toughness fracture. The rheological properties of the PMMA@PB/BADCy resin show that the PMMA@PB core-shell rubber has insignificant influence on the rheological properties of BADCy resin. The lowest viscosity of the PMMA@PB/BADCy resin is 0.79 Pa·s, which is the ideal viscosity to impregnate fiber for preparing prepreg. The dielectric properties at different frequencies show that the PMMA@PB core-shell rubber has little effect on the dielectric properties of toughened BADCy. When 6wt% PMMA@PB core-shell rubber is used, the dielectric constant is 3.0 and the dielectric loss is about 0.010. The PMMA@PB/BADCy resin system presents excellent performances and can be used as matrix of prepreg. It is suitable for the manufacture of low dielectric composites in aerospace.
2018, 35(3): 521-527.
doi: 10.13801/j.cnki.fhclxb.20170511.003
Abstract:
The carbon fiber reinforced polylactic acid (CF/PLA) composites were specially prepared, with carbon fiber treated by nitric acid oxidation. The effect of pulsed electromagnetic fields (PEF) on the CF/PLA composite degradation characteristics under that treating condition was explored. The results show that, carbon fiber surface treatment has influences on the water absorption of CF/PLA composites mass retention, bending strength and shearing strength varying degrees under the PEF action. The analysis combined with the previous studies shows that the ester bonding formed by the carbon fiber surface treatment has existence of a sort of change under the role of PEF, which leads to specificity of the interface degradation of CF/PLA. The study is expected to provide a solution of synergistic control from the material itself and the external conditions degradable to improve CF/PLA internal fracture fixation device.
The carbon fiber reinforced polylactic acid (CF/PLA) composites were specially prepared, with carbon fiber treated by nitric acid oxidation. The effect of pulsed electromagnetic fields (PEF) on the CF/PLA composite degradation characteristics under that treating condition was explored. The results show that, carbon fiber surface treatment has influences on the water absorption of CF/PLA composites mass retention, bending strength and shearing strength varying degrees under the PEF action. The analysis combined with the previous studies shows that the ester bonding formed by the carbon fiber surface treatment has existence of a sort of change under the role of PEF, which leads to specificity of the interface degradation of CF/PLA. The study is expected to provide a solution of synergistic control from the material itself and the external conditions degradable to improve CF/PLA internal fracture fixation device.
2018, 35(3): 528-536.
doi: 10.13801/j.cnki.fhclxb.20170511.001
Abstract:
Cyanate ester-epoxy resin(CE75) with 75% cyanate ester's mass fraction and high modulus carbon fiber reinforced CE75 resin (CF/CE75) composites were prepared. The processing property, cure schedule, thermal stability and mechanical properties of CE75 resin were studied. Furthermore, high modulus CF/CE75 composites were treated in simulated space environment, and then the mechanical properties and outgassing properties were investigated. The results show that CE75 resin possesses excellent processing properties, which are suitable for wet winding molding. The glass transition temperature and the initial decrease temperature of storage modulus of the CE75 resin are 195.6℃ and 368.6℃, respectively, indicating that the CE75 resin has good thermal properties. High modulus CF/CE75 pipes also presents excellent space-environment-resistant properties. After being exposed to vacuum condition, the outgassing behavior of the composites achieves the international standards. The results of thermal cycling test (-196-130℃) shows that the mechanical properties of pipes remain more than 96% after 200 cycles. Therefore, high modulus CF/CE75 composites will be a potential ideal candidate for the space-environment-resistant composites.
Cyanate ester-epoxy resin(CE75) with 75% cyanate ester's mass fraction and high modulus carbon fiber reinforced CE75 resin (CF/CE75) composites were prepared. The processing property, cure schedule, thermal stability and mechanical properties of CE75 resin were studied. Furthermore, high modulus CF/CE75 composites were treated in simulated space environment, and then the mechanical properties and outgassing properties were investigated. The results show that CE75 resin possesses excellent processing properties, which are suitable for wet winding molding. The glass transition temperature and the initial decrease temperature of storage modulus of the CE75 resin are 195.6℃ and 368.6℃, respectively, indicating that the CE75 resin has good thermal properties. High modulus CF/CE75 pipes also presents excellent space-environment-resistant properties. After being exposed to vacuum condition, the outgassing behavior of the composites achieves the international standards. The results of thermal cycling test (-196-130℃) shows that the mechanical properties of pipes remain more than 96% after 200 cycles. Therefore, high modulus CF/CE75 composites will be a potential ideal candidate for the space-environment-resistant composites.
2018, 35(3): 537-544.
doi: 10.13801/j.cnki.fhclxb.20170523.001
Abstract:
In order to improve the damping performance of natural rubber (NR), it was blended in mass ratio of 20:80 with epoxidized natural rubber (ENR) of different epoxidation degrees in a mixer to obtain blend rubber matrix of ENR-NR. The ENR-NR matrix was further filled in mixing and smelting process with other components (sulfur, accelerator 2,2'-dibenzothiazole disulfde(DM), promoter N-cyclohexylbenzothiazde-2-sulphenamide(CZ), ZnO, stearic acid, carbon black) to prepare a wide temperature-range damping ENR-NR matrix composites. The dynamic mechanical properties and the damping characteristics of the plasticized ENR-NR mixtures and their vulcanized rubbers were tested by rubber processing analyzer (RPA) and DMA. The results show that epoxidation of NR enhances the rigidity local molecular chain and improves the adhesion between the matrix and the fillers while ENR adsorbing more carbon black is inhomogeneously dispersed in the continuous phase NR. ENR and its blend rubber with NR exhibit higher viscosity and storage modulus for ENR with higher epoxied degree. The combination of ENR into NR can obtain materials with better elastic and damping performances for vulcanizates when damping range is widened to higher temperature for ENR-NR compound rubber. The effective range is -57-1℃ for ENR-NR with epoxidation degree 25 in comparison with -57——20℃ for NR although there is ineffective damping zone for composite rubber when natural rubber being epoxidized to higher degree. However, the addition of a small amount of ENR has little effect on the hardness, modulus and elongation at break of NR matrix composite.
In order to improve the damping performance of natural rubber (NR), it was blended in mass ratio of 20:80 with epoxidized natural rubber (ENR) of different epoxidation degrees in a mixer to obtain blend rubber matrix of ENR-NR. The ENR-NR matrix was further filled in mixing and smelting process with other components (sulfur, accelerator 2,2'-dibenzothiazole disulfde(DM), promoter N-cyclohexylbenzothiazde-2-sulphenamide(CZ), ZnO, stearic acid, carbon black) to prepare a wide temperature-range damping ENR-NR matrix composites. The dynamic mechanical properties and the damping characteristics of the plasticized ENR-NR mixtures and their vulcanized rubbers were tested by rubber processing analyzer (RPA) and DMA. The results show that epoxidation of NR enhances the rigidity local molecular chain and improves the adhesion between the matrix and the fillers while ENR adsorbing more carbon black is inhomogeneously dispersed in the continuous phase NR. ENR and its blend rubber with NR exhibit higher viscosity and storage modulus for ENR with higher epoxied degree. The combination of ENR into NR can obtain materials with better elastic and damping performances for vulcanizates when damping range is widened to higher temperature for ENR-NR compound rubber. The effective range is -57-1℃ for ENR-NR with epoxidation degree 25 in comparison with -57——20℃ for NR although there is ineffective damping zone for composite rubber when natural rubber being epoxidized to higher degree. However, the addition of a small amount of ENR has little effect on the hardness, modulus and elongation at break of NR matrix composite.
2018, 35(3): 545-552.
doi: 10.13801/j.cnki.fhclxb.20170420.002
Abstract:
An ethynyl phenyl azo novolac resin(EPAN) was prepared by Diazo coupling reaction.The ethynyl-containing phenolic resin was used to modify the silicon-containing arylacetylene resin (PSA) through solution blending. The thermal properties of the modified PSA were studied. The modified PSA-EPAN was used to prepare the carbon fabric prepregs. The T300 carbon fabric (T300CF) reinforced the modified PSA-EPAN composites were thermally press-molded, and the mechanical properties of the composites were further investigated. The results show that the EPAN can be well distributed in the PSA matrix, and the cure temperature of the PSA-EPAN blend resin enhances. With mass fraction of 7% EPAN in the PSA-EPAN blend resin, the residual yield at 800℃ in N2 of the cured blend resin is more than 90%, and the glass transition temperature of the cured blend resin is more than 500℃. The flexural strength of the cured PSA-EPAN blend resin reaches 40.7 MPa which is more than that of the cured PSA resin and increases by 95.5%. The flexural strength and interlayer shear strength of the T300 carbon fabric reinforced PSA-EPAN blend resin composite can reach 423.5 MPa and 29.5 MPa, increasing by 74% and 65%, respectively.
An ethynyl phenyl azo novolac resin(EPAN) was prepared by Diazo coupling reaction.The ethynyl-containing phenolic resin was used to modify the silicon-containing arylacetylene resin (PSA) through solution blending. The thermal properties of the modified PSA were studied. The modified PSA-EPAN was used to prepare the carbon fabric prepregs. The T300 carbon fabric (T300CF) reinforced the modified PSA-EPAN composites were thermally press-molded, and the mechanical properties of the composites were further investigated. The results show that the EPAN can be well distributed in the PSA matrix, and the cure temperature of the PSA-EPAN blend resin enhances. With mass fraction of 7% EPAN in the PSA-EPAN blend resin, the residual yield at 800℃ in N2 of the cured blend resin is more than 90%, and the glass transition temperature of the cured blend resin is more than 500℃. The flexural strength of the cured PSA-EPAN blend resin reaches 40.7 MPa which is more than that of the cured PSA resin and increases by 95.5%. The flexural strength and interlayer shear strength of the T300 carbon fabric reinforced PSA-EPAN blend resin composite can reach 423.5 MPa and 29.5 MPa, increasing by 74% and 65%, respectively.
2018, 35(3): 553-563.
doi: 10.13801/j.cnki.fhclxb.20170517.002
Abstract:
Quasi-static and dynamic nanoindentation techniques were performed to study the surface mechanical properties of hydroxyapatite/polylactic acid (HA/PLA) composites on the nanoscale. The mechanical responses(modulus and hardness) of the composite were obtained by changing the loading and holding time in the static mode. The effects of these experimental parameters on nanoindentation measurement were also discussed. It is found that the loading and unloading time have a significant effect on the experimental results due to creep deformation when the holding time is less than 45 s. It is also found that a "nose" may appear in the unloading segment of the load-displacement curve during nanoindentation when the holding time is short and the unloading time is long. The holding time was set to 45 s in order to avoid the influence of the "nose". The dynamic nanomechanical properties of the material were investigated in the dynamic indentation mode. The results show that the storage modulus and hardness decrease with the increase of the indentation depth. Both nanoindentation and scratch test show that HA improves the mechanical properties of PLA obviously. Comparing with pure PLA, the modulus and hardness of 9wt% HA/PLA composite enhance by 35.5% and 44.7%.The creep depth of 9wt% HA/PLA composites decreases by 9.5%. The maximum depth and residual depth are fewer than that of pure PLA under the same load, showing the greater elastic recovery and resilience of HA/PLA composites.
Quasi-static and dynamic nanoindentation techniques were performed to study the surface mechanical properties of hydroxyapatite/polylactic acid (HA/PLA) composites on the nanoscale. The mechanical responses(modulus and hardness) of the composite were obtained by changing the loading and holding time in the static mode. The effects of these experimental parameters on nanoindentation measurement were also discussed. It is found that the loading and unloading time have a significant effect on the experimental results due to creep deformation when the holding time is less than 45 s. It is also found that a "nose" may appear in the unloading segment of the load-displacement curve during nanoindentation when the holding time is short and the unloading time is long. The holding time was set to 45 s in order to avoid the influence of the "nose". The dynamic nanomechanical properties of the material were investigated in the dynamic indentation mode. The results show that the storage modulus and hardness decrease with the increase of the indentation depth. Both nanoindentation and scratch test show that HA improves the mechanical properties of PLA obviously. Comparing with pure PLA, the modulus and hardness of 9wt% HA/PLA composite enhance by 35.5% and 44.7%.The creep depth of 9wt% HA/PLA composites decreases by 9.5%. The maximum depth and residual depth are fewer than that of pure PLA under the same load, showing the greater elastic recovery and resilience of HA/PLA composites.
2018, 35(3): 564-571.
doi: 10.13801/j.cnki.fhclxb.20170601.002
Abstract:
To get a lightweight anti-blast structure, short-cut glass fiber reinforced composite (SMC) and carbon fiber reinforced plastics (CFRP) were adopted to design and make stiffened plate. Finite element simulation based on LS-DYNA reveals that the composite stiffened panel has excellent anti-blast ability through large elastic deformation and the panel will rebound back completely with little residual deformation. Parametrized analyses reveal that transverse bars greatly influence the maximum flexure of the stiffened plates under blast. Their contribution to the rigidity of the panel is much greater than the longitudinal reinforcement and the skin. Applying equivalent volume conversion method, the stiffened panel is simplified as a uniform panel and the dynamic response of the composite stiffened panel is predicted theoretically. Precision and validity of the prediction in flexure are testified by the numerical simulation.
To get a lightweight anti-blast structure, short-cut glass fiber reinforced composite (SMC) and carbon fiber reinforced plastics (CFRP) were adopted to design and make stiffened plate. Finite element simulation based on LS-DYNA reveals that the composite stiffened panel has excellent anti-blast ability through large elastic deformation and the panel will rebound back completely with little residual deformation. Parametrized analyses reveal that transverse bars greatly influence the maximum flexure of the stiffened plates under blast. Their contribution to the rigidity of the panel is much greater than the longitudinal reinforcement and the skin. Applying equivalent volume conversion method, the stiffened panel is simplified as a uniform panel and the dynamic response of the composite stiffened panel is predicted theoretically. Precision and validity of the prediction in flexure are testified by the numerical simulation.
2018, 35(3): 572-579.
doi: 10.13801/j.cnki.fhclxb.20170608.002
Abstract:
The tensile and compressive stress-strain relationships of bamboo scrimber were studied in this paper. The uniaxial longitudinal tension and compression tests were carried out to investigate the failure modes and the characteristics of the stress-strain relationships of bamboo scrimber. The results indicate that the tensile failure modes show as brittle tensile failure, and the compressive failure modes show as buckling failure, shearing failure and wedge split failure. According to the test results, the tensile stress-strain relationship of bamboo scrimber is linear until failure, and the compressive stress-strain curves of bamboo scrimber can be divided into three stages:elastic stage, elastic-plastic stage and platform stage. A linear elastic model was suggested for the tensile tress-strain relationship for bamboo scrimber; three models were presented for the compressive tress-strain relationship, namely trilinear model, general model and exponential model.The results indicate that three presented models can describe the three stages of the stress-strain curves of the bamboo scrimber under axial compression. Totally, the predicted results of the proposed models are in good agreement with the experimental results.
The tensile and compressive stress-strain relationships of bamboo scrimber were studied in this paper. The uniaxial longitudinal tension and compression tests were carried out to investigate the failure modes and the characteristics of the stress-strain relationships of bamboo scrimber. The results indicate that the tensile failure modes show as brittle tensile failure, and the compressive failure modes show as buckling failure, shearing failure and wedge split failure. According to the test results, the tensile stress-strain relationship of bamboo scrimber is linear until failure, and the compressive stress-strain curves of bamboo scrimber can be divided into three stages:elastic stage, elastic-plastic stage and platform stage. A linear elastic model was suggested for the tensile tress-strain relationship for bamboo scrimber; three models were presented for the compressive tress-strain relationship, namely trilinear model, general model and exponential model.The results indicate that three presented models can describe the three stages of the stress-strain curves of the bamboo scrimber under axial compression. Totally, the predicted results of the proposed models are in good agreement with the experimental results.
2018, 35(3): 580-590.
doi: 10.13801/j.cnki.fhclxb.20170531.001
Abstract:
In order to study the effect of mold factors on fiber volume content, resin-rich and curing distortions of composite, a series of V-shaped T700/QY9611 composite parts were cured through autoclave process and the fiber volume, resin-rich area and spring-in were measured and studied. A three-dimensional finite element analysis (FEA) model considering the effect of thermal load, resin cure shrinkage, mold contact, fiber volume content and resin-rich was built to simulate the spring-in of V-shaped parts, and the effect of fiber content gradient and resin-rich on spring-in was quantitatively analyzed. The results show that there will be 10% of fiber volume content gradient and 2.2 mm thick resin-rich area in V-shaped parts fabricated on female mold and the value reduce to 6.8% and 1.2 mm for larger corner radius mold, meanwhile, mold materials have little effect on fiber volume content and resin-rich area. The spring-in of test specimens fabricated on female mold increase by 21.0% than male mold, and decrease by 9.6% with larger corner radius female mold. The female mold mainly affects spring-in through fiber volume content and resin-rich area. The simulation results show that spring-in are proportional to fiber volume content gradient and thickness of resin-rich area. 10% of fiber volume content gradient will lead to 13.5% of spring-in difference and 3.0 mm thick resin-rich area will result in 45.8% of spring-in difference. The comparison between simulation results and experiment verifies the model.
In order to study the effect of mold factors on fiber volume content, resin-rich and curing distortions of composite, a series of V-shaped T700/QY9611 composite parts were cured through autoclave process and the fiber volume, resin-rich area and spring-in were measured and studied. A three-dimensional finite element analysis (FEA) model considering the effect of thermal load, resin cure shrinkage, mold contact, fiber volume content and resin-rich was built to simulate the spring-in of V-shaped parts, and the effect of fiber content gradient and resin-rich on spring-in was quantitatively analyzed. The results show that there will be 10% of fiber volume content gradient and 2.2 mm thick resin-rich area in V-shaped parts fabricated on female mold and the value reduce to 6.8% and 1.2 mm for larger corner radius mold, meanwhile, mold materials have little effect on fiber volume content and resin-rich area. The spring-in of test specimens fabricated on female mold increase by 21.0% than male mold, and decrease by 9.6% with larger corner radius female mold. The female mold mainly affects spring-in through fiber volume content and resin-rich area. The simulation results show that spring-in are proportional to fiber volume content gradient and thickness of resin-rich area. 10% of fiber volume content gradient will lead to 13.5% of spring-in difference and 3.0 mm thick resin-rich area will result in 45.8% of spring-in difference. The comparison between simulation results and experiment verifies the model.
2018, 35(3): 591-598.
doi: 10.13801/j.cnki.fhclxb.20170601.003
Abstract:
The in-plane shear performance for F-12 aramid fabric was investigated. The picture frame test and bias-tensile test were conducted. A new picture clamp was designed. The deformation field of fabric during the test was measured by digital image correlation (DIC) technique. The shear force vs. shear angle curves and the locked angle were obtained. Normalized method was used to compare the two experimental results. Then, numerical method was used to compute the shear characters. A non-orthogonal anisotropic truss-shell model was established to simulate the bias-tensile test. A user defined material subroutine was developed to calculate the direction of the yarns and stress updated. To verify the validity of the model, the simulated results were compared with experimental results. The test results show that the shear performance of the fabric is non-linear. The clamping arm can affect the test results. The force of no silts sample is larger than that of infinite slits sample. The locked angles of these two samples are equal. After normalized, the force of picture frame test is larger than that of bias-tensile test, while the locked angle is smaller. The FEM results agree well with experimental results.
The in-plane shear performance for F-12 aramid fabric was investigated. The picture frame test and bias-tensile test were conducted. A new picture clamp was designed. The deformation field of fabric during the test was measured by digital image correlation (DIC) technique. The shear force vs. shear angle curves and the locked angle were obtained. Normalized method was used to compare the two experimental results. Then, numerical method was used to compute the shear characters. A non-orthogonal anisotropic truss-shell model was established to simulate the bias-tensile test. A user defined material subroutine was developed to calculate the direction of the yarns and stress updated. To verify the validity of the model, the simulated results were compared with experimental results. The test results show that the shear performance of the fabric is non-linear. The clamping arm can affect the test results. The force of no silts sample is larger than that of infinite slits sample. The locked angles of these two samples are equal. After normalized, the force of picture frame test is larger than that of bias-tensile test, while the locked angle is smaller. The FEM results agree well with experimental results.
2018, 35(3): 599-606.
doi: 10.13801/j.cnki.fhclxb.20170612.003
Abstract:
Curvilinear fiber format is one of the effective ways to improve the mechanical properties of composite components.The laying trajectories of open-hole composite laminates were investigated. B-spline interpolation was used to obtain the laying trajectory of open-hole composite laminates with the maximum principal stress. The variable stiffness open-hole composite laminate model was established by discrete grid method.The tensile failure numerical simulation and damage failure analysis were carried out by Tsai-Wu damage failure criterion and constant stiffness degradation criterion. Two sets of constant stiffness and variable stiffness open-hole composite laminates experimental specimens were placed, respectively. A tensile strength experiment was performed.The results show that the numerical simulation accurately captures the data from experiment. The tensile strength of variable stiffness open-hole composite laminates, compared with constant stiffness open-hole composite laminates, increases by 26.92%, and the damage evolution processes of both are significantly different.
Curvilinear fiber format is one of the effective ways to improve the mechanical properties of composite components.The laying trajectories of open-hole composite laminates were investigated. B-spline interpolation was used to obtain the laying trajectory of open-hole composite laminates with the maximum principal stress. The variable stiffness open-hole composite laminate model was established by discrete grid method.The tensile failure numerical simulation and damage failure analysis were carried out by Tsai-Wu damage failure criterion and constant stiffness degradation criterion. Two sets of constant stiffness and variable stiffness open-hole composite laminates experimental specimens were placed, respectively. A tensile strength experiment was performed.The results show that the numerical simulation accurately captures the data from experiment. The tensile strength of variable stiffness open-hole composite laminates, compared with constant stiffness open-hole composite laminates, increases by 26.92%, and the damage evolution processes of both are significantly different.
2018, 35(3): 607-615.
doi: 10.13801/j.cnki.fhclxb.20170612.004
Abstract:
The temperature effect on transverse compressive behaviors of 3D braided carbon fiber/epoxy composites was investigated in low temperature fields (20, 0, -50, -100℃). The experiments were performed and the finite element method was adopted. The results indicate that the temperature has influence on the transverse compressive modulus, yield stress and tangent modulus of 3D braided carbon fiber/epoxy composites at different levels. The surface morphologies of 3D braided carbon fiber/epoxy composites after transverse compression are also influenced by temperature significantly. At low temperature, the surface scaly pattern of 3D braided carbon fiber/epoxy composites reduces and the yarn-matrix interfacial crack occurs. The temperature reduction gives rise to the internal thermal stress, but the thermal stress has a limited influence on the mechanical behavior and is not the main factor in temperature effect. The property variation of epoxy matrix with temperature is the main mechanism for the temperature effect on transverse compression of 3D braided carbon fiber/epoxy composites.
The temperature effect on transverse compressive behaviors of 3D braided carbon fiber/epoxy composites was investigated in low temperature fields (20, 0, -50, -100℃). The experiments were performed and the finite element method was adopted. The results indicate that the temperature has influence on the transverse compressive modulus, yield stress and tangent modulus of 3D braided carbon fiber/epoxy composites at different levels. The surface morphologies of 3D braided carbon fiber/epoxy composites after transverse compression are also influenced by temperature significantly. At low temperature, the surface scaly pattern of 3D braided carbon fiber/epoxy composites reduces and the yarn-matrix interfacial crack occurs. The temperature reduction gives rise to the internal thermal stress, but the thermal stress has a limited influence on the mechanical behavior and is not the main factor in temperature effect. The property variation of epoxy matrix with temperature is the main mechanism for the temperature effect on transverse compression of 3D braided carbon fiber/epoxy composites.
2018, 35(3): 616-622.
doi: 10.13801/j.cnki.fhclxb.20170531.003
Abstract:
The TiB2/Cu composites with TiB2 mass fraction of 1wt%-5wt% were prepared by spark plasma sintering (SPS), and the electrical conductivity and hardness were tested. The electrical conductivity of TiB2/Cu composites decreases from 96.9% (International Annealed Copper Standard, IACS) to 65.1%(IACS) with TiB2 mass fraction increasing from 0 to 5wt%, while the Brinell hardness increases from 42.8 to 65.2. To discuss the effect of TiB2 content and current on TiB2/Cu composites arc erosion, the electrical contact tests were performed at 24 V and different direct current for TiB2/Cu composites with the different TiB2 mass fractions. For TiB2/Cu composites with different TiB2 mass fraction, the average arc duration, average arc energy and mass loss increase with the increase of current. The cathode of TiB2/Cu composites mass loss more than that of the anode. In general, the TiB2/Cu composites are transferred from cathode to anode. At 24 V and 25 A, the arc duration and arc energy of TiB2/Cu composites with different TiB2 mass fractions are fluctuant with the increase of operation times. On the whole, it shows a tendency to increase gradually. The 3wt% TiB2/Cu composite has higher stability, the average arc duration and average arc energy are lower than the others. With the increase of mass fraction of TiB2, TiB2/Cu composites present less mass loss and shallower arc erosion pits.
The TiB2/Cu composites with TiB2 mass fraction of 1wt%-5wt% were prepared by spark plasma sintering (SPS), and the electrical conductivity and hardness were tested. The electrical conductivity of TiB2/Cu composites decreases from 96.9% (International Annealed Copper Standard, IACS) to 65.1%(IACS) with TiB2 mass fraction increasing from 0 to 5wt%, while the Brinell hardness increases from 42.8 to 65.2. To discuss the effect of TiB2 content and current on TiB2/Cu composites arc erosion, the electrical contact tests were performed at 24 V and different direct current for TiB2/Cu composites with the different TiB2 mass fractions. For TiB2/Cu composites with different TiB2 mass fraction, the average arc duration, average arc energy and mass loss increase with the increase of current. The cathode of TiB2/Cu composites mass loss more than that of the anode. In general, the TiB2/Cu composites are transferred from cathode to anode. At 24 V and 25 A, the arc duration and arc energy of TiB2/Cu composites with different TiB2 mass fractions are fluctuant with the increase of operation times. On the whole, it shows a tendency to increase gradually. The 3wt% TiB2/Cu composite has higher stability, the average arc duration and average arc energy are lower than the others. With the increase of mass fraction of TiB2, TiB2/Cu composites present less mass loss and shallower arc erosion pits.
2018, 35(3): 623-631.
doi: 10.13801/j.cnki.fhclxb.20170608.005
Abstract:
The effect of holes on initial electrical resistivity and piezoresistive coefficients was investigated by taking constantan as an example. The relationship between average stresses and average electrical resistivity of an inhomogeneous composites with holes was replaced by that of a homogeneous material. The homogenization method was used to calculate initial electrical resistivity and piezoresistive coefficients of a square plate with holes. The conclusions can be summarized as follows. Initial electrical resistivity and piezoresistive coefficients π11, π22 of constantan material increase with the increase of volume fraction of holes, and piezoresistive coefficients π12, π21 decrease. Effect of triangle holes on initial electrical resistivity and piezoresistive coefficients of constantan material is the most obvious.
The effect of holes on initial electrical resistivity and piezoresistive coefficients was investigated by taking constantan as an example. The relationship between average stresses and average electrical resistivity of an inhomogeneous composites with holes was replaced by that of a homogeneous material. The homogenization method was used to calculate initial electrical resistivity and piezoresistive coefficients of a square plate with holes. The conclusions can be summarized as follows. Initial electrical resistivity and piezoresistive coefficients π11, π22 of constantan material increase with the increase of volume fraction of holes, and piezoresistive coefficients π12, π21 decrease. Effect of triangle holes on initial electrical resistivity and piezoresistive coefficients of constantan material is the most obvious.
2018, 35(3): 632-639.
doi: 10.13801/j.cnki.fhclxb.20170504.001
Abstract:
The shear properties of graphene/copper composites were systematically studied by molecular dynamics method, including shear elastic modulus, shear yield strength, shear failure strength and shear deformation mechanism. It is found that the addition of graphene significantly improves the shear strength of the graphene/copper composites and the shear strength increases with the increasing of the volume fraction of graphene. The graphene layer in the composites has synergistic effect with the copper layer, i.e. the graphene layer prevents the copper dislocation propagation, and the copper layer blocks the buckling of the graphene structure. The shear properties of the graphene/copper composites with spherical defects were also investigated. The results show that the small size defects with different number and location have little effect on the shear properties of the composites. The graphene/copper composites with small defect still have good performance and application value. But with the increasing of the diameter of the defects, the shear strength of the composites decreases distinctly.
The shear properties of graphene/copper composites were systematically studied by molecular dynamics method, including shear elastic modulus, shear yield strength, shear failure strength and shear deformation mechanism. It is found that the addition of graphene significantly improves the shear strength of the graphene/copper composites and the shear strength increases with the increasing of the volume fraction of graphene. The graphene layer in the composites has synergistic effect with the copper layer, i.e. the graphene layer prevents the copper dislocation propagation, and the copper layer blocks the buckling of the graphene structure. The shear properties of the graphene/copper composites with spherical defects were also investigated. The results show that the small size defects with different number and location have little effect on the shear properties of the composites. The graphene/copper composites with small defect still have good performance and application value. But with the increasing of the diameter of the defects, the shear strength of the composites decreases distinctly.
2018, 35(3): 640-646.
doi: 10.13801/j.cnki.fhclxb.20170519.002
Abstract:
A ZrB2-SiC ceramic coating was prepared on C/C-SiC composites by slurry painting and high temperature sintering to improve the ablation property of C/C-SiC composites at ultra high temperatures. The phase composition and microstructure of the ZrB2-SiC coating were analyzed by EDS and SEM. The mechanical and ablation properties of the coatings were investigated. The results show that the tensile strength, flexural strength and shear strength of the C/C-SiC composites protected by ZrB2-SiC coatings are 147 MPa, 355 MPa and 21.9 MPa, respectively. The mechanical properties of the coated C/C-SiC composites are little lower than the counterpart properties of the uncoated C/C-SiC composites. The coated C/C-SiC composite has an outstanding ablation property. After ablation by oxyacetylene torch test at a heat flux of 3 200 kW/m2 for 600 s, the coated sample has an average mass ablation rate of 0.001 mm/s and an average linear ablation rate of 0.0006 g/s.
A ZrB2-SiC ceramic coating was prepared on C/C-SiC composites by slurry painting and high temperature sintering to improve the ablation property of C/C-SiC composites at ultra high temperatures. The phase composition and microstructure of the ZrB2-SiC coating were analyzed by EDS and SEM. The mechanical and ablation properties of the coatings were investigated. The results show that the tensile strength, flexural strength and shear strength of the C/C-SiC composites protected by ZrB2-SiC coatings are 147 MPa, 355 MPa and 21.9 MPa, respectively. The mechanical properties of the coated C/C-SiC composites are little lower than the counterpart properties of the uncoated C/C-SiC composites. The coated C/C-SiC composite has an outstanding ablation property. After ablation by oxyacetylene torch test at a heat flux of 3 200 kW/m2 for 600 s, the coated sample has an average mass ablation rate of 0.001 mm/s and an average linear ablation rate of 0.0006 g/s.
2018, 35(3): 647-652.
doi: 10.13801/j.cnki.fhclxb.20170519.003
Abstract:
x wt% Al2O3(x=0, 1.0, 1.5)/BaTi0.85Sn0.15O3(BTS) ceramics were prepared by the traditional secondary solid state reaction method. And the effects of BTS ceramics doped with Al2O3 on the microstructure, dielectricity and flexoelectricity were studied. The results show that BTS ceramics doped with Al2O3 are still the standard perovskite crystal structure, Al2O3 reduces the size of the grain effectively. When Al2O3 doping amount increases, the dielectric constant of Al2O3/BTS ceramics decreases, the dielectric loss of Al2O3/BTS ceramics decreases, the Curie peaks broaden and shift to the high temperature direction. With the increase of Al2O3 content and test temperature, the flexoelectric coefficient of Al2O3/BTS ceramics decreases.And there is a near linear relationship between the coefficient of deflection and dielectric constant of Al2O3/BTS ceramics, but when the temperature is very close to the Curie temperature, the linear relationship is weakened.
x wt% Al2O3(x=0, 1.0, 1.5)/BaTi0.85Sn0.15O3(BTS) ceramics were prepared by the traditional secondary solid state reaction method. And the effects of BTS ceramics doped with Al2O3 on the microstructure, dielectricity and flexoelectricity were studied. The results show that BTS ceramics doped with Al2O3 are still the standard perovskite crystal structure, Al2O3 reduces the size of the grain effectively. When Al2O3 doping amount increases, the dielectric constant of Al2O3/BTS ceramics decreases, the dielectric loss of Al2O3/BTS ceramics decreases, the Curie peaks broaden and shift to the high temperature direction. With the increase of Al2O3 content and test temperature, the flexoelectric coefficient of Al2O3/BTS ceramics decreases.And there is a near linear relationship between the coefficient of deflection and dielectric constant of Al2O3/BTS ceramics, but when the temperature is very close to the Curie temperature, the linear relationship is weakened.
2018, 35(3): 653-660.
doi: 10.13801/j.cnki.fhclxb.20170601.008
Abstract:
Air-coupled ultrasonic testing technology, possessing the characteristics of non-contact and non-destruction, is widely used in nondestructive detection for materials. An air-based line-focus air-coupled ultrasonic transducer was designed and fabricated according to the measurement of crystalline silicon solar cells. Compared to the ultrasonic transducer based on the traditional polymer matrix, the air-based line-focus air-coupled ultrasonic transducer adopted the 3D printing method to hollow out the polymer matrix frame, which will further reduce the acoustic impedance of piezoelectric composites. The center frequency of the transducer is about 150 kHz, and the focus radius is 20 mm, aperture is 28 mm. The generating and receiving performance of the transducer was measured. An crack detection experiment was implemented on a monocrystalline solar cell by air-coupled Lamb waves. The crack can be located by analyzing the amplitude of the received signals, furthermore, a correlation analysis was performed to extract the characteristics of the cracks.
Air-coupled ultrasonic testing technology, possessing the characteristics of non-contact and non-destruction, is widely used in nondestructive detection for materials. An air-based line-focus air-coupled ultrasonic transducer was designed and fabricated according to the measurement of crystalline silicon solar cells. Compared to the ultrasonic transducer based on the traditional polymer matrix, the air-based line-focus air-coupled ultrasonic transducer adopted the 3D printing method to hollow out the polymer matrix frame, which will further reduce the acoustic impedance of piezoelectric composites. The center frequency of the transducer is about 150 kHz, and the focus radius is 20 mm, aperture is 28 mm. The generating and receiving performance of the transducer was measured. An crack detection experiment was implemented on a monocrystalline solar cell by air-coupled Lamb waves. The crack can be located by analyzing the amplitude of the received signals, furthermore, a correlation analysis was performed to extract the characteristics of the cracks.
2018, 35(3): 661-667.
doi: 10.13801/j.cnki.fhclxb.20170601.004
Abstract:
The carbonized graphene oxide(GO)/chitosan composites were prepared by atmosphere sintering in Ar atmosphere at 600℃, 700℃, 800℃ and 900℃. The carbonized GO/chitosan composites were characterized by XRD, SEM, FTIR and electrochemical station. The results indicate that the carbonized GO/chitosan composites exhibit the significant improvement (around 67%) in mechanical properties comparing with pristine chitosan. The specific capacitance of the carbonized GO/chitosan sample fabricated at 800℃ is about 131 F/g, the specific capacitance retention after 1 500 cycles is higher than 97%.
The carbonized graphene oxide(GO)/chitosan composites were prepared by atmosphere sintering in Ar atmosphere at 600℃, 700℃, 800℃ and 900℃. The carbonized GO/chitosan composites were characterized by XRD, SEM, FTIR and electrochemical station. The results indicate that the carbonized GO/chitosan composites exhibit the significant improvement (around 67%) in mechanical properties comparing with pristine chitosan. The specific capacitance of the carbonized GO/chitosan sample fabricated at 800℃ is about 131 F/g, the specific capacitance retention after 1 500 cycles is higher than 97%.
2018, 35(3): 668-675.
doi: 10.13801/j.cnki.fhclxb.20170609.001
Abstract:
Slag, lime, cement and gypsum were used as the cementitious agents to prepare the cementitious agent/soil composites. The hygrothermal properties of the cementitious agent/soil composites were investigated by guarded hot plate method and isothermal absorption and desorption method. The test results present that both cementitious type and content have significant effect on the hygrothermal properties of the cementitious agent/soil composites. Hygrothermal properties of the cementitious agent/soil composites were comprehensively analyzed by normalization method, the results show that 10% gypsum/soil composite has the best hygrothermal comprehensive property. The reason is that a mesh structure, which provides a structural supporting in the matrix, is formed by hydration of gypsum. The pores, which existe in the mesh structure, decrease the thermal conductivity of the cementitious agent/soil composites and increase the absorption property.
Slag, lime, cement and gypsum were used as the cementitious agents to prepare the cementitious agent/soil composites. The hygrothermal properties of the cementitious agent/soil composites were investigated by guarded hot plate method and isothermal absorption and desorption method. The test results present that both cementitious type and content have significant effect on the hygrothermal properties of the cementitious agent/soil composites. Hygrothermal properties of the cementitious agent/soil composites were comprehensively analyzed by normalization method, the results show that 10% gypsum/soil composite has the best hygrothermal comprehensive property. The reason is that a mesh structure, which provides a structural supporting in the matrix, is formed by hydration of gypsum. The pores, which existe in the mesh structure, decrease the thermal conductivity of the cementitious agent/soil composites and increase the absorption property.
2018, 35(3): 676-683.
doi: 10.13801/j.cnki.fhclxb.20170609.006
Abstract:
Butyl stearate was impregnated into pores of expanded perlite, and limestone powder wrapped up it to prepare phase-changing energy-storing aggregates (PCESA). Phase-changing energy-storing concrete was prepared by PCESA replacing some sand. Experiments of compressive strength and splitting tensile strength were carried out for phase-changing energy-storing concrete. The micro-morphology of phase-changing energy-storing concrete was characterized by using SEM images. Both phase transition properties of PCESA and specific heat capacity of phase-changing energy-storing concrete were characterized by DSC technique. The test results show that:The PCESA remain intact in phase-changing energy-storing concrete, and interfacial transition zone (ITZ) is typical attribute of phase-changing energy-storing concrete with good integrity between cement paste and PCESA, which leads to the increase of phase-changing energy-storing concrete strength relatively. The increase of PCESA volume fraction results in a rising of specific heat capacity of phase-changing energy-storing concrete due to the good thermo-physical performance of PCESA. When the content of PCESA is up to 20vol%, the phase-changing energy-storing concrete has a good mechanical and thermo-physical performance, and it is equally amenable to bearing capacity and building energy conservation.
Butyl stearate was impregnated into pores of expanded perlite, and limestone powder wrapped up it to prepare phase-changing energy-storing aggregates (PCESA). Phase-changing energy-storing concrete was prepared by PCESA replacing some sand. Experiments of compressive strength and splitting tensile strength were carried out for phase-changing energy-storing concrete. The micro-morphology of phase-changing energy-storing concrete was characterized by using SEM images. Both phase transition properties of PCESA and specific heat capacity of phase-changing energy-storing concrete were characterized by DSC technique. The test results show that:The PCESA remain intact in phase-changing energy-storing concrete, and interfacial transition zone (ITZ) is typical attribute of phase-changing energy-storing concrete with good integrity between cement paste and PCESA, which leads to the increase of phase-changing energy-storing concrete strength relatively. The increase of PCESA volume fraction results in a rising of specific heat capacity of phase-changing energy-storing concrete due to the good thermo-physical performance of PCESA. When the content of PCESA is up to 20vol%, the phase-changing energy-storing concrete has a good mechanical and thermo-physical performance, and it is equally amenable to bearing capacity and building energy conservation.
2018, 35(3): 684-689.
doi: 10.13801/j.cnki.fhclxb.20170601.005
Abstract:
The nano-sized CeO2/graphene catalyst was synthesized by hydrothermal method using bean sprouts with rich and graded porous structure as template. XRD, Raman spectroscopy, TEM, field emission scanning electron microscopy (FESEM), UV-Vis diffuse reflectance spectroscopy (UV-Vis/DRS) were adopted to characterize the structure and morphology of CeO2/graphene catalyst, as well as the photocatalytic performance. The results show that the prepared CeO2/graphene photocatalyst not only inherits the characteristics of high porosity and large specific surface area of bean sprouts, but also maintains the morphological and microscopic characteristics of bean sprouts. The catalyst is composed of about 5.6 nm CeO2 nanocrystals combined with a biologically morphic bionic graphene sheet structure. The as-prepared CeO2/graphene composite possesses a large number of nanopores formed by the accumulation of catalyst nanoparticles, and their pore sizes distribute at about 15-45 nm, which makes the CeO2/graphene catalyst have large specific surface area and improves the capture of the photo-generated electron-hole pairs ability. The visible light utilization efficiency of CeO2/graphene composites is significantly enhanced by the UV-visible diffuse reflectance spectrum, and 671 μmol(h·g)-1 is obtained after 6 h of photolytic water, which is much higher than that of the standard CeO2 of 51.67 μmol(h·g)-1.
The nano-sized CeO2/graphene catalyst was synthesized by hydrothermal method using bean sprouts with rich and graded porous structure as template. XRD, Raman spectroscopy, TEM, field emission scanning electron microscopy (FESEM), UV-Vis diffuse reflectance spectroscopy (UV-Vis/DRS) were adopted to characterize the structure and morphology of CeO2/graphene catalyst, as well as the photocatalytic performance. The results show that the prepared CeO2/graphene photocatalyst not only inherits the characteristics of high porosity and large specific surface area of bean sprouts, but also maintains the morphological and microscopic characteristics of bean sprouts. The catalyst is composed of about 5.6 nm CeO2 nanocrystals combined with a biologically morphic bionic graphene sheet structure. The as-prepared CeO2/graphene composite possesses a large number of nanopores formed by the accumulation of catalyst nanoparticles, and their pore sizes distribute at about 15-45 nm, which makes the CeO2/graphene catalyst have large specific surface area and improves the capture of the photo-generated electron-hole pairs ability. The visible light utilization efficiency of CeO2/graphene composites is significantly enhanced by the UV-visible diffuse reflectance spectrum, and 671 μmol(h·g)-1 is obtained after 6 h of photolytic water, which is much higher than that of the standard CeO2 of 51.67 μmol(h·g)-1.
2018, 35(3): 690-698.
doi: 10.13801/j.cnki.fhclxb.20170821.004
Abstract:
Multiple admixtures (e.g. Fly ash, silica fume, slag, expansion agent, air-entrained water reduce agent (AEWRA) and cementitious capillary crystalline waterproofing material (CCCWM)) were added in concrete. Five groups concrete mix was designed, and experiments were conducted to study the damage, mass loss rate, dynamic elastic modulus, erosion-resistance coefficients, with multi-salt soaking and wetting-drying cyclic and freezing-thawing. The microstructure corrosion mechanisms were revealed by SEM, EDS and XRD. The results show that a limitation in improvement of erosion resistance is only for mixing with fly ash and silica fume. Nevertheless, it is significant to improve the erosion resistance of the fly ash and silica fume mixture in which certain amount of expansion agent are added. The dynamic elastic modulus is above 80%, and the erosion-resistance coefficients are above 0.9 after 11 cycles in multi-salt soaking and wetting-drying cyclic and freezing-thawing. CCCWM mixed into concrete can reduce the erosion resistance, the dynamic elastic modulus is below 60%, and the erosion-resistance coefficients are reduced from 1.0 to 0.3 after 4 cycles of multi-salt soaking and wetting-drying cyclic and freezing-thawing. The corrosion products for ettringite and calcium carbonate are found that multi-salt soaking under wetting-drying and freezing-thawing cycles will accelerate corrosion of the concrete, using microscopic mechanism analysis.
Multiple admixtures (e.g. Fly ash, silica fume, slag, expansion agent, air-entrained water reduce agent (AEWRA) and cementitious capillary crystalline waterproofing material (CCCWM)) were added in concrete. Five groups concrete mix was designed, and experiments were conducted to study the damage, mass loss rate, dynamic elastic modulus, erosion-resistance coefficients, with multi-salt soaking and wetting-drying cyclic and freezing-thawing. The microstructure corrosion mechanisms were revealed by SEM, EDS and XRD. The results show that a limitation in improvement of erosion resistance is only for mixing with fly ash and silica fume. Nevertheless, it is significant to improve the erosion resistance of the fly ash and silica fume mixture in which certain amount of expansion agent are added. The dynamic elastic modulus is above 80%, and the erosion-resistance coefficients are above 0.9 after 11 cycles in multi-salt soaking and wetting-drying cyclic and freezing-thawing. CCCWM mixed into concrete can reduce the erosion resistance, the dynamic elastic modulus is below 60%, and the erosion-resistance coefficients are reduced from 1.0 to 0.3 after 4 cycles of multi-salt soaking and wetting-drying cyclic and freezing-thawing. The corrosion products for ettringite and calcium carbonate are found that multi-salt soaking under wetting-drying and freezing-thawing cycles will accelerate corrosion of the concrete, using microscopic mechanism analysis.
2018, 35(3): 699-705.
doi: 10.13801/j.cnki.fhclxb.20170601.009
Abstract:
In order to study on the fatigue and self-healing characteristics of asphalt mortar, the dynamic shear rheometer (DSR) was utilized to test time sweep and fatigue-healing-fatigue, and the microstructure was observed by Atomic Force Microscopy (AFM), and the fatigue performance of asphalt mortar and styrene butadiene styrene block copolymer(SBS) modified asphalt mortar under different powder binder ratios and self-healing properties of 3 different intermittent periods at normal atmospheric temperature (25℃) were analyzed and compared. It's found that SBS asphalt mortar has better fatigue and self healing properties, the fatigue life of two kinds asphalt mortar increases with powder binder ratio, and longer intermittent period is beneficial to self-healing under the same powder binder ratio. AFM observations show that matrix asphalt mortar appears "bee like structure" obviously, and asphaltene is absorbed and "bee like structure" becomes more, so the cohesion between filler and asphalt is enhanced, and fatigue properties is also improved with the increase of powder binder ratio. SBS modifier has good compatibility with asphalt, not a "bee like structure", and the addition of the modifier greatly enhances the cohesion between the molecules, also it is conducive to improve the fatigue properties, so it is recommended that modified asphalt mortar is used as pavement material.
In order to study on the fatigue and self-healing characteristics of asphalt mortar, the dynamic shear rheometer (DSR) was utilized to test time sweep and fatigue-healing-fatigue, and the microstructure was observed by Atomic Force Microscopy (AFM), and the fatigue performance of asphalt mortar and styrene butadiene styrene block copolymer(SBS) modified asphalt mortar under different powder binder ratios and self-healing properties of 3 different intermittent periods at normal atmospheric temperature (25℃) were analyzed and compared. It's found that SBS asphalt mortar has better fatigue and self healing properties, the fatigue life of two kinds asphalt mortar increases with powder binder ratio, and longer intermittent period is beneficial to self-healing under the same powder binder ratio. AFM observations show that matrix asphalt mortar appears "bee like structure" obviously, and asphaltene is absorbed and "bee like structure" becomes more, so the cohesion between filler and asphalt is enhanced, and fatigue properties is also improved with the increase of powder binder ratio. SBS modifier has good compatibility with asphalt, not a "bee like structure", and the addition of the modifier greatly enhances the cohesion between the molecules, also it is conducive to improve the fatigue properties, so it is recommended that modified asphalt mortar is used as pavement material.
2018, 35(3): 706-713.
doi: 10.13801/j.cnki.fhclxb.20170613.001
Abstract:
Environmental and water cutting rubber powder (RP)-natural rubber (NR) composites and surfaces modification rubber powder (MRP)-NR composites were prepared. Effects of the content of RP and water cutting rubber powder(WRP) on the mechanical and dynamic mechanical properties of the composites were investigated. The infrared and thermogravimetric analysis show that the main rubber of the RP is NR and styrene-butadiene rubber (SBR).The structure of the main chain has no obvious change by modification, which was confirmed by thermogravimetric analysis. The processing property of MRP-NR composites was characterized by rubber process analyzer and the dispersion of rubber powder was characterized by a carbon black dispersing instrument. The results show that the compatibility of the MRP and NR has been improved and the processing property of MRP-NR composites is better than RP-NR composites. The dispersion of RP in NR gets worse with the increase content of RP, compared with the RP, MRP gets more separation and distribution in NR matrix, the tensile strength of MRP-NR composites is 27.9 MPa.
Environmental and water cutting rubber powder (RP)-natural rubber (NR) composites and surfaces modification rubber powder (MRP)-NR composites were prepared. Effects of the content of RP and water cutting rubber powder(WRP) on the mechanical and dynamic mechanical properties of the composites were investigated. The infrared and thermogravimetric analysis show that the main rubber of the RP is NR and styrene-butadiene rubber (SBR).The structure of the main chain has no obvious change by modification, which was confirmed by thermogravimetric analysis. The processing property of MRP-NR composites was characterized by rubber process analyzer and the dispersion of rubber powder was characterized by a carbon black dispersing instrument. The results show that the compatibility of the MRP and NR has been improved and the processing property of MRP-NR composites is better than RP-NR composites. The dispersion of RP in NR gets worse with the increase content of RP, compared with the RP, MRP gets more separation and distribution in NR matrix, the tensile strength of MRP-NR composites is 27.9 MPa.
2018, 35(3): 714-721.
doi: 10.13801/j.cnki.fhclxb.20170613.002
Abstract:
In order to prevent the premature end-debonding of externally bonded fiber reinforced polymer (FRP) composite used for shear strengthening of reinforced concrete (RC) beams, a novel self-locking anchorage for FRP sheet was developed and a hybrid-anchoring method for FRP U-sheet was proposed, which was bonding the FRP to the surfaces of a beam and anchoring the FRP ends by anchor plates. Five specimens were tested to validate the feasibility of the new method, including two control specimen, one specimen strengthened by externally bonded (EB) U-sheets of carbon fiber reinforced polymer(CFRP) and two specimens strengthened by hybrid-anchored U-sheets. The results show that hybrid anchorage can shift the end-debonding of CFRP to the rupture failure and greatly improve the fiber-strength utilization. It performs much better than the conventional method of externally bonding in the aspects of restraining the propagation of the diagonal crack, improving the strain behavior of steel stirrups and CFRP, and increasing the shear capacity of RC beam.
In order to prevent the premature end-debonding of externally bonded fiber reinforced polymer (FRP) composite used for shear strengthening of reinforced concrete (RC) beams, a novel self-locking anchorage for FRP sheet was developed and a hybrid-anchoring method for FRP U-sheet was proposed, which was bonding the FRP to the surfaces of a beam and anchoring the FRP ends by anchor plates. Five specimens were tested to validate the feasibility of the new method, including two control specimen, one specimen strengthened by externally bonded (EB) U-sheets of carbon fiber reinforced polymer(CFRP) and two specimens strengthened by hybrid-anchored U-sheets. The results show that hybrid anchorage can shift the end-debonding of CFRP to the rupture failure and greatly improve the fiber-strength utilization. It performs much better than the conventional method of externally bonding in the aspects of restraining the propagation of the diagonal crack, improving the strain behavior of steel stirrups and CFRP, and increasing the shear capacity of RC beam.
2018, 35(3): 722-731.
doi: 10.13801/j.cnki.fhclxb.20170612.005
Abstract:
In order to investigate the effect of short and long steel fibers on the flexural response of ultra high performance concrete(UHPC), 3 groups of mono-fiber and 10 groups of hybrid-fiber reinforced UHPCs were designed and cubic compression test and four points bending test were performed. Test results show that:for mono-fiber reinforced UHPC, the highest bending stress is 19.98 MPa with a fiber volume content of 5vol% and the bending stress decreases if more fibers are added. For hybrid-fiber reinforced UHPC, bending stress is higher than the mono-fiber reinforced UHPC, the highest bending stress is 23.55 MPa with a fiber volume content of 2vol% and 1vol% for long and short steel fibers, respectively. The flexural response of steel fiber/UHPC is dominantly affected by the volume content of long fibers rather than that of short fibers. The mechanical performance such as bending strength, ductility and flexural toughness are not simply affected by the volume content of long fibers, the balance of volume contents between long and short steel fibers is very critical, the optimal result tested in this experiment is the group of 2vol% and 1vol% for long and short fibers, respectively.
In order to investigate the effect of short and long steel fibers on the flexural response of ultra high performance concrete(UHPC), 3 groups of mono-fiber and 10 groups of hybrid-fiber reinforced UHPCs were designed and cubic compression test and four points bending test were performed. Test results show that:for mono-fiber reinforced UHPC, the highest bending stress is 19.98 MPa with a fiber volume content of 5vol% and the bending stress decreases if more fibers are added. For hybrid-fiber reinforced UHPC, bending stress is higher than the mono-fiber reinforced UHPC, the highest bending stress is 23.55 MPa with a fiber volume content of 2vol% and 1vol% for long and short steel fibers, respectively. The flexural response of steel fiber/UHPC is dominantly affected by the volume content of long fibers rather than that of short fibers. The mechanical performance such as bending strength, ductility and flexural toughness are not simply affected by the volume content of long fibers, the balance of volume contents between long and short steel fibers is very critical, the optimal result tested in this experiment is the group of 2vol% and 1vol% for long and short fibers, respectively.
