2015 Vol. 32, No. 5
2015, 32(5): 1233-1240.
doi: 10.13801/j.cnki.fhclxb.20150729.004
Abstract:
We demonstrate the recent research progress of the series novel graphene-based ordered mesoporous metal oxide composites grounded on the special 3D structure of ordered mesoporous metal oxides and the supporter of graphene, as well as the synergistic effect of coexistence. The exploratory study for controlledly synthesis of ordered mesoporous metal oxides, effective combination with graphene and photoelectric properties of composites in our lab were introduced. We outline the preparation method, formation mechanism of graphene-based ordered mesoporous metal oxide composites and their novel applications in catalysis, electrochemistry, sensing and energy storage area. The future developments of graphene-based ordered mesoporous metal oxide composites have also been prospected.
We demonstrate the recent research progress of the series novel graphene-based ordered mesoporous metal oxide composites grounded on the special 3D structure of ordered mesoporous metal oxides and the supporter of graphene, as well as the synergistic effect of coexistence. The exploratory study for controlledly synthesis of ordered mesoporous metal oxides, effective combination with graphene and photoelectric properties of composites in our lab were introduced. We outline the preparation method, formation mechanism of graphene-based ordered mesoporous metal oxide composites and their novel applications in catalysis, electrochemistry, sensing and energy storage area. The future developments of graphene-based ordered mesoporous metal oxide composites have also been prospected.
2015, 32(5): 1241-1251.
doi: 10.13801/j.cnki.fhclxb.20141028.002
Abstract:
Owing to the excellent comprehensive mechanical performance, 3D multi-directional braided composites have tremendous application potentials as primary load-bearing structures in the aeronautics and astronautics fields. Finite element analysis (FEA) is the most economical and effective analysis method to study the macro-meso mechanical properties of 3D multi-directional braided composites. The research progresses of meso finite element methods, including the meso structure model, stiffness and strength property prediction and interface property analysis, were reviewed. Moreover, the research status of macro finite element method, including impact property simulation, load-bearing property analysis of joint structures and so on, were also introduced. The main problems existing in the present research were analyzed and the subsequent work was prospected, which provides convenient references for researchers to understand the current research situation and development trends in this field.
Owing to the excellent comprehensive mechanical performance, 3D multi-directional braided composites have tremendous application potentials as primary load-bearing structures in the aeronautics and astronautics fields. Finite element analysis (FEA) is the most economical and effective analysis method to study the macro-meso mechanical properties of 3D multi-directional braided composites. The research progresses of meso finite element methods, including the meso structure model, stiffness and strength property prediction and interface property analysis, were reviewed. Moreover, the research status of macro finite element method, including impact property simulation, load-bearing property analysis of joint structures and so on, were also introduced. The main problems existing in the present research were analyzed and the subsequent work was prospected, which provides convenient references for researchers to understand the current research situation and development trends in this field.
2015, 32(5): 1252-1259.
doi: 10.13801/j.cnki.fhclxb.20141222.001
Abstract:
In order to significantly improve the mechanical properties and thermal endurance of poly(butylene succinate), the micron hexagonal boron nitride (h-BN) was treated with silane coupling agent KH550, and blended with PBS to modify PBS. The high thermal endurance h-BN-KH550/PBS composite films were prepared through melt blending and rolling mill process. The particle structure of h-BN-KH550 and the mechanical properties, aggregation state structure, fracture morphologies, crystallization property and thermal stability of composite films were investigated. The results reveal that the mechanical properties of h-BN-KH550/PBS composite films are greatly improved compared with PBS. When the mass ratio of KH550 to h-BN is 2:50 and h-BN-KH550 to PBS is 3:50, the comprehensive mechanical properties are optimal. The h-BN-KH550 particles are well dispersed in PBS. During the crystallization process of PBS, h-BN-KH550 can act as nucleating agent and increase the crystallization rate and crystallinity of PBS. The thermal stability of h-BN-KH550/PBS composite films is significantly increased. When the mass ratio of h-BN-KH550 to PBS is 3:50, the temperatures at 5%, 10%, 50% mass loss (T5d, T10d,T50d) and the peak of pyrolysis temperature (Tp) are increased by 30.0, 22.6, 9.5 and 10.0 ℃ during the pyrolysis process of composite films, respectively.
In order to significantly improve the mechanical properties and thermal endurance of poly(butylene succinate), the micron hexagonal boron nitride (h-BN) was treated with silane coupling agent KH550, and blended with PBS to modify PBS. The high thermal endurance h-BN-KH550/PBS composite films were prepared through melt blending and rolling mill process. The particle structure of h-BN-KH550 and the mechanical properties, aggregation state structure, fracture morphologies, crystallization property and thermal stability of composite films were investigated. The results reveal that the mechanical properties of h-BN-KH550/PBS composite films are greatly improved compared with PBS. When the mass ratio of KH550 to h-BN is 2:50 and h-BN-KH550 to PBS is 3:50, the comprehensive mechanical properties are optimal. The h-BN-KH550 particles are well dispersed in PBS. During the crystallization process of PBS, h-BN-KH550 can act as nucleating agent and increase the crystallization rate and crystallinity of PBS. The thermal stability of h-BN-KH550/PBS composite films is significantly increased. When the mass ratio of h-BN-KH550 to PBS is 3:50, the temperatures at 5%, 10%, 50% mass loss (T5d, T10d,T50d) and the peak of pyrolysis temperature (Tp) are increased by 30.0, 22.6, 9.5 and 10.0 ℃ during the pyrolysis process of composite films, respectively.
2015, 32(5): 1260-1270.
doi: 10.13801/j.cnki.fhclxb.20141216.002
Abstract:
In order to explore the reinforced structure effects on the flexural strength of carbon fiber reinforced polymer matrix composites (CF-PMCs) after thermal-oxidative aging, the thermal-oxidative aging properties of 3D four-directional braided carbon fiber/epoxy composites (3D braided composites for short) and laminated plain weave carbon fabric/epoxy composites (laminated composites for short) were studied. The samples before and after thermos-oxidative aging were analyzed by means of FTIR, aging mass loss, bending test and SEM. The results indicate that the oxidation chain scissions of matrix resin and the degradation of the bonding force of fiber/matrix interface caused by thermal-oxidative aging are the reasons for the decrease of the flexural strength and flexural modulus of the two kinds of composites. Flexural strength is more easily affected by thermal-oxidative aging than flexural modulus. Under the same thermal-oxidative aging conditions, the thermal-oxidative aging mass loss of laminated composites is larger than that of 3D braided composites, but the flexural strength and flexural modulus retention rates of the 3D braided composites are greater than those of laminated composites. After age at 140 ℃ for 1 200 h, the flexural strength and flexural modulus retention rates of laminated composites are 74.7% and 88.3%, respectively, and those of corresponding 3D braided composites are 79.4% and 91.5%, respectively. Therefore, adopting 3D braided preform as the reinforcement of CF-PMCs is an effective way to improve the thermo-oxidative stability.
In order to explore the reinforced structure effects on the flexural strength of carbon fiber reinforced polymer matrix composites (CF-PMCs) after thermal-oxidative aging, the thermal-oxidative aging properties of 3D four-directional braided carbon fiber/epoxy composites (3D braided composites for short) and laminated plain weave carbon fabric/epoxy composites (laminated composites for short) were studied. The samples before and after thermos-oxidative aging were analyzed by means of FTIR, aging mass loss, bending test and SEM. The results indicate that the oxidation chain scissions of matrix resin and the degradation of the bonding force of fiber/matrix interface caused by thermal-oxidative aging are the reasons for the decrease of the flexural strength and flexural modulus of the two kinds of composites. Flexural strength is more easily affected by thermal-oxidative aging than flexural modulus. Under the same thermal-oxidative aging conditions, the thermal-oxidative aging mass loss of laminated composites is larger than that of 3D braided composites, but the flexural strength and flexural modulus retention rates of the 3D braided composites are greater than those of laminated composites. After age at 140 ℃ for 1 200 h, the flexural strength and flexural modulus retention rates of laminated composites are 74.7% and 88.3%, respectively, and those of corresponding 3D braided composites are 79.4% and 91.5%, respectively. Therefore, adopting 3D braided preform as the reinforcement of CF-PMCs is an effective way to improve the thermo-oxidative stability.
2015, 32(5): 1271-1278.
doi: 10.13801/j.cnki.fhclxb.20150306.002
Abstract:
As long time load-bearing implants such as meniscus and cartilages, the fatigue behavior of poly(vinyl alcohol) (PVA) composite hydrogel in physical environment relates to persistence and stability of the implants. The nano bacterial cellulose (BC) was dispersed evenly into PVA hydrogel matrix to prepare nano BC/PVA composite hydrogels by method of dispersive strengthening. To investigate and evaluate the anti-fatigue property and mechanical stability of composite hydrogels in simulated body fluid (SBF) environments, three methods including compression fatigue process analysis, stiffness variation analysis and dimensional stability analysis before and after fatigue were used.The results show that the nano BC/PVA composite hydrogels have excellent anti-fatigue property in simulated body environments, which can meet the requirements of anti-fatigue property for implant in body. By adding nano BC, the mechanical stability and anti-fatigue property of composite hydrogels are improved effectively, but as the addition of nano BC increasing further, the anti-fatigue property of composite hydrogels is reduced. When the mass ratio of PVA to nano BC is 30:1, the nano BC/PVA composite hydrogels show the least maximum displacement increment (0.002 mm), the minimum change of stiffness (5.41%) and the best dimensional stability before and after fatigue, the deformation amount is merely 0.427 mm, and the fatigue property is the best.
As long time load-bearing implants such as meniscus and cartilages, the fatigue behavior of poly(vinyl alcohol) (PVA) composite hydrogel in physical environment relates to persistence and stability of the implants. The nano bacterial cellulose (BC) was dispersed evenly into PVA hydrogel matrix to prepare nano BC/PVA composite hydrogels by method of dispersive strengthening. To investigate and evaluate the anti-fatigue property and mechanical stability of composite hydrogels in simulated body fluid (SBF) environments, three methods including compression fatigue process analysis, stiffness variation analysis and dimensional stability analysis before and after fatigue were used.The results show that the nano BC/PVA composite hydrogels have excellent anti-fatigue property in simulated body environments, which can meet the requirements of anti-fatigue property for implant in body. By adding nano BC, the mechanical stability and anti-fatigue property of composite hydrogels are improved effectively, but as the addition of nano BC increasing further, the anti-fatigue property of composite hydrogels is reduced. When the mass ratio of PVA to nano BC is 30:1, the nano BC/PVA composite hydrogels show the least maximum displacement increment (0.002 mm), the minimum change of stiffness (5.41%) and the best dimensional stability before and after fatigue, the deformation amount is merely 0.427 mm, and the fatigue property is the best.
2015, 32(5): 1279-1285.
doi: 10.13801/j.cnki.fhclxb.20150327.002
Abstract:
In order to improve the arc-resistance ablation property of polytetrafluoroethylene (PTFE) nozzle composites of high voltage circuit breaker, micro or nano size boron nitride (BN) or aluminium nitride (AlN) with different ratios were dispersed into PFTE matrix. CO2 continuous laser was used for ablating PTFE nozzle material to simulate electric arc ablation process. The effects of light reflectance, thermal conductivity and relative dielectric constants on ablation amount were analyzed. By comparing ablation amount of composites and numerical analytical results, the key factors affecting ablation amount are thermal parameters of materials (thermal conductivity and thermal diffusion coefficient). BN/PTFE composites have higher ablation resistance property compared with AlN/PTFE composites. The thermal conductivity of 10.0% BN/PTFE composites is up to 0.46 W/(m·K) which is 92% higher than that of pure PTFE. The mass loss of 10.0% BN/PTFE composits in ablation process is 21.8 mg, which is 47% less than that of 3.0% AlN/PTFE composites. The ablation resistance property of nozzle composites is effectively improved.
In order to improve the arc-resistance ablation property of polytetrafluoroethylene (PTFE) nozzle composites of high voltage circuit breaker, micro or nano size boron nitride (BN) or aluminium nitride (AlN) with different ratios were dispersed into PFTE matrix. CO2 continuous laser was used for ablating PTFE nozzle material to simulate electric arc ablation process. The effects of light reflectance, thermal conductivity and relative dielectric constants on ablation amount were analyzed. By comparing ablation amount of composites and numerical analytical results, the key factors affecting ablation amount are thermal parameters of materials (thermal conductivity and thermal diffusion coefficient). BN/PTFE composites have higher ablation resistance property compared with AlN/PTFE composites. The thermal conductivity of 10.0% BN/PTFE composites is up to 0.46 W/(m·K) which is 92% higher than that of pure PTFE. The mass loss of 10.0% BN/PTFE composits in ablation process is 21.8 mg, which is 47% less than that of 3.0% AlN/PTFE composites. The ablation resistance property of nozzle composites is effectively improved.
2015, 32(5): 1286-1293.
doi: 10.13801/j.cnki.fhclxb.20150113.001
Abstract:
This paper aims at dispersing nano Al2O3 in polyethylene(PE) and ethylene vinyl acetate copolymer (EVA) blends to build thermal conductive composites with high local particle concentration and selective distribution structure. With nano Al2O3 as thermal conductive filler, PE and EVA as matrix resin, Al2O3/PE-EVA thermal conductive composites were prepared by melt blending method. The phase structure of PE-EVA blends and distribution of Al2O3 in blends were investigated by selective solution extraction method and SEM. The thermal conductivity and mechanical properties of Al2O3/PE-EVA composites were evaluated. The results show that blends with two-phase co-continuous structure are obtained at PE to EVA mass ratio of 1:1. By introducing Al2O3 into PE-EVA two-phase co-continuous blends, Al2O3 is mainly dispersed in PE phase. The distribution behavior of Al2O3 and the formation of co-continuous structure are helpful to improve the thermal conductivity of composites. 21.2% increase of thermal conductivity is obtained for Al2O3/PE-EVA composites with selective distribution and co-continuous structure, in comparison to that of Al2O3/PE composites at Al2O3 mass fraction of 50%. With the increase of Al2O3 mass fraction, the tensile strength of Al2O3/PE-EVA composites tends to be similar to that of Al2O3/PE composites. The elongation at break of Al2O3/PE-EVA composites is also superior than that of Al2O3/PE composites thanks to the toughing effect of EVA phase.
This paper aims at dispersing nano Al2O3 in polyethylene(PE) and ethylene vinyl acetate copolymer (EVA) blends to build thermal conductive composites with high local particle concentration and selective distribution structure. With nano Al2O3 as thermal conductive filler, PE and EVA as matrix resin, Al2O3/PE-EVA thermal conductive composites were prepared by melt blending method. The phase structure of PE-EVA blends and distribution of Al2O3 in blends were investigated by selective solution extraction method and SEM. The thermal conductivity and mechanical properties of Al2O3/PE-EVA composites were evaluated. The results show that blends with two-phase co-continuous structure are obtained at PE to EVA mass ratio of 1:1. By introducing Al2O3 into PE-EVA two-phase co-continuous blends, Al2O3 is mainly dispersed in PE phase. The distribution behavior of Al2O3 and the formation of co-continuous structure are helpful to improve the thermal conductivity of composites. 21.2% increase of thermal conductivity is obtained for Al2O3/PE-EVA composites with selective distribution and co-continuous structure, in comparison to that of Al2O3/PE composites at Al2O3 mass fraction of 50%. With the increase of Al2O3 mass fraction, the tensile strength of Al2O3/PE-EVA composites tends to be similar to that of Al2O3/PE composites. The elongation at break of Al2O3/PE-EVA composites is also superior than that of Al2O3/PE composites thanks to the toughing effect of EVA phase.
2015, 32(5): 1294-1300.
doi: 10.13801/j.cnki.fhclxb.20141224.002
Abstract:
In order to research the influence of bacterial cellulose (BC) network structure on crystal and melting process of polylactic acid (PLA), PLA and BC were selected as the matrix and the reinforcement to prepare BC/PLA biological composites with interpenetrating network structure via blending diffusion of PLA-chloroform solution and BC-anhydrous ethanol dispersion. The micro-morphology, spherulite morphology, non-isothermal crystallization kinetics and melting behavior of the composites were investigated by SEM, polarized optical microscopy (POM), DSC and MO's model. The results show that the solution blending diffusion method is available for the preparation of composites with interpenetrating network structure of PLA wound on the surface of BC skeleton. The crystallization temperature, melting temperature and relative crystallinity of BC/PLA composites decrease with the increasing of cooling rate. As a heterogeneous nucleating agent, proper amount BC can improve the crystallization rate and relative crystallinity and refine the spherulite simultaneously. MO's model can describe the non-isothermal crystallization kinetics behavior of BC/PLA composites very well.
In order to research the influence of bacterial cellulose (BC) network structure on crystal and melting process of polylactic acid (PLA), PLA and BC were selected as the matrix and the reinforcement to prepare BC/PLA biological composites with interpenetrating network structure via blending diffusion of PLA-chloroform solution and BC-anhydrous ethanol dispersion. The micro-morphology, spherulite morphology, non-isothermal crystallization kinetics and melting behavior of the composites were investigated by SEM, polarized optical microscopy (POM), DSC and MO's model. The results show that the solution blending diffusion method is available for the preparation of composites with interpenetrating network structure of PLA wound on the surface of BC skeleton. The crystallization temperature, melting temperature and relative crystallinity of BC/PLA composites decrease with the increasing of cooling rate. As a heterogeneous nucleating agent, proper amount BC can improve the crystallization rate and relative crystallinity and refine the spherulite simultaneously. MO's model can describe the non-isothermal crystallization kinetics behavior of BC/PLA composites very well.
2015, 32(5): 1301-1308.
doi: 10.13801/j.cnki.fhclxb.20141224.004
Abstract:
The polyamide nonwoven fabric (PNF) was chosen as structural toughening layer, and carbon fiber reinforced epoxy composites toughened by interlaminar PNF (U3160-PNF/3266) were fabricated by resin transfer molding (RTM) process. The moisture absorption properties of U3160-PNF/3266 composites and the influence of hygrothermal aging on heat resistant performance of it were investigated. The results indicate that composites have similar moisture absorption dynamics characteristics before and after toughening. But the moisture absorption rate of U3160-PNF/3266 composites is much larger at the original moisture absorption. The saturated moisture absorption rate of U3160-PNF/3266 composites is 0.96%, which is a little greater than that of untoughened composites (U3160/3266) of 0.87%. The glass transition temperatures of the two composites both decrease with the increment of hygrothermal aging time, and are going to be stable as the moisture absorption rate saturate. Up to the saturated moisture absorption, the glass transition temperatures of U3160-PNF/3266 and U3160/3266 composites are reduced by approximately 15% and 14% respectively.
The polyamide nonwoven fabric (PNF) was chosen as structural toughening layer, and carbon fiber reinforced epoxy composites toughened by interlaminar PNF (U3160-PNF/3266) were fabricated by resin transfer molding (RTM) process. The moisture absorption properties of U3160-PNF/3266 composites and the influence of hygrothermal aging on heat resistant performance of it were investigated. The results indicate that composites have similar moisture absorption dynamics characteristics before and after toughening. But the moisture absorption rate of U3160-PNF/3266 composites is much larger at the original moisture absorption. The saturated moisture absorption rate of U3160-PNF/3266 composites is 0.96%, which is a little greater than that of untoughened composites (U3160/3266) of 0.87%. The glass transition temperatures of the two composites both decrease with the increment of hygrothermal aging time, and are going to be stable as the moisture absorption rate saturate. Up to the saturated moisture absorption, the glass transition temperatures of U3160-PNF/3266 and U3160/3266 composites are reduced by approximately 15% and 14% respectively.
2015, 32(5): 1309-1315.
doi: 10.13801/j.cnki.fhclxb.20150105.001
Abstract:
Graphene oxide (GO) is one of the most important derivatives of graphene. GO nanosheets/epoxy composites were prepared by oxidization and ultrasonic dispersion. The structure and morphology of GO nanosheets were characterized by XRD, Raman spectrum, FTIR and TEM. The effects of GO nanosheet content on the thermal stability, mechanical property and dielectric property of GO nanosheets/epoxy composites were discussed. The results show that the thermal stability of GO nanosheets/epoxy composites is improved by adding GO nanosheets. The impact strength and bending strength first increase and then decrease with increasing GO nanosheets loading. Dielectric constant and dielectric loss first decrease and then increase. The thermal decomposition temperature with 5% mass loss is improved from 400.2 ℃ for the pure epoxy to 424.5 ℃ for the GO nanosheets/epoxy composites with 0.3wt% GO nanosheets loading. Furthermore, the impact strength and bending strength with 0.2wt% and 0.3wt% GO nanosheets loading reach the maximum respectively, increasing from 10.5 kJ/m2 for the pure epoxy to 19.7 kJ/m2 and from 80.5 MPa to 104.0 MPa.
Graphene oxide (GO) is one of the most important derivatives of graphene. GO nanosheets/epoxy composites were prepared by oxidization and ultrasonic dispersion. The structure and morphology of GO nanosheets were characterized by XRD, Raman spectrum, FTIR and TEM. The effects of GO nanosheet content on the thermal stability, mechanical property and dielectric property of GO nanosheets/epoxy composites were discussed. The results show that the thermal stability of GO nanosheets/epoxy composites is improved by adding GO nanosheets. The impact strength and bending strength first increase and then decrease with increasing GO nanosheets loading. Dielectric constant and dielectric loss first decrease and then increase. The thermal decomposition temperature with 5% mass loss is improved from 400.2 ℃ for the pure epoxy to 424.5 ℃ for the GO nanosheets/epoxy composites with 0.3wt% GO nanosheets loading. Furthermore, the impact strength and bending strength with 0.2wt% and 0.3wt% GO nanosheets loading reach the maximum respectively, increasing from 10.5 kJ/m2 for the pure epoxy to 19.7 kJ/m2 and from 80.5 MPa to 104.0 MPa.
2015, 32(5): 1316-1320.
doi: 10.13801/j.cnki.fhclxb.20150120.002
Abstract:
Glass fiber/epoxy composites have high insulation and high mechanical properties. They are usually employed as the supporting materials in high energy physics and nuclear physics tests. But the mechanical properties will vary in irradiation environments. As one kind of glass fiber/epoxy composites, glass-cloth/epoxy laminated sheet is employed according to the application requirements of new generation Beijing Electron and Positron Collider (BEPCII). The compression properties of glass-cloth/epoxy laminated sheet before and after γ irradiation were studied. The result shows that the compression strength of glass-cloth/epoxy laminated sheet reduces to 315.05 MPa from 320.21 MPa after the γ irradiation of 20 kGy, declining by 1.61%. The compression strength of glass-cloth/epoxy laminated sheet reduces to 312.30 MPa after the γ irradiation of 200 kGy, declining by 2.47%. The fracture sections of the samples before and after irradiation were observed by SEM.The results show the glass-cloth does not change obviously and the binding degree of the glass-cloth and the epoxy declines after irradiation. The fragmentation of epoxy is more obvious. FTIR spectra indicates that the degradation reaction predominates over the crosslinking reaction of epoxy after irradiation.
Glass fiber/epoxy composites have high insulation and high mechanical properties. They are usually employed as the supporting materials in high energy physics and nuclear physics tests. But the mechanical properties will vary in irradiation environments. As one kind of glass fiber/epoxy composites, glass-cloth/epoxy laminated sheet is employed according to the application requirements of new generation Beijing Electron and Positron Collider (BEPCII). The compression properties of glass-cloth/epoxy laminated sheet before and after γ irradiation were studied. The result shows that the compression strength of glass-cloth/epoxy laminated sheet reduces to 315.05 MPa from 320.21 MPa after the γ irradiation of 20 kGy, declining by 1.61%. The compression strength of glass-cloth/epoxy laminated sheet reduces to 312.30 MPa after the γ irradiation of 200 kGy, declining by 2.47%. The fracture sections of the samples before and after irradiation were observed by SEM.The results show the glass-cloth does not change obviously and the binding degree of the glass-cloth and the epoxy declines after irradiation. The fragmentation of epoxy is more obvious. FTIR spectra indicates that the degradation reaction predominates over the crosslinking reaction of epoxy after irradiation.
2015, 32(5): 1321-1329.
doi: 10.13801/j.cnki.fhclxb.20141216.001
Abstract:
Using heat-resistant polyethylene (PE-RT) pipe materials as matrix, conductive carbon black master batch (remarked as CBE) carried by ethylene-vinyl acetate copolymer (EVA) as conductive medium, with 3.86wt% of polyethylene-octene copolymer elastomer (POE), via twin-screw extrusion process, PE-RT antistatic pipe material with conductive mesh structure was prepared, reducing the percolation threshold of composite system, and comparing it to system with addition of conductive carbon black (remarked as CB) to study the electrical properties, morphology structure, rheological properties, mechanical properties and thermal stability in CB/PE-RT and CBE/POE/PE-RT composite system. The results show that it produces a synergistic effect between POE and EVA, the addition of POE changes the differences of viscoelastic between PE-RT and EVA, so that EVA reaches percolation to form a continuous network structure in matrix, and CB disperses preferentially in EVA phase with low viscosity, higher polar, POE plays an inhibitory effect on migration of CB from EVA phase to PE-RT phase, then CB reaches percolation in EVA phase easily. Finally it forms a conductive network structure because of dual role of percolation. CB improves the crystallization property of PE-RT and thermal stability of CBE/POE/PE-RT composite system, and CB has little effects on the mechanical properties of CBE/POE/PE-RT composite system, to a certain extent, it solves the contradiction between conductivity and mechanical properties of filled-type conductivity systems. POE has a plasticizing effect on composite system, maintaining the advantages of PE-RT pipes that can be bent, expanding the application scope of plastic pipe.
Using heat-resistant polyethylene (PE-RT) pipe materials as matrix, conductive carbon black master batch (remarked as CBE) carried by ethylene-vinyl acetate copolymer (EVA) as conductive medium, with 3.86wt% of polyethylene-octene copolymer elastomer (POE), via twin-screw extrusion process, PE-RT antistatic pipe material with conductive mesh structure was prepared, reducing the percolation threshold of composite system, and comparing it to system with addition of conductive carbon black (remarked as CB) to study the electrical properties, morphology structure, rheological properties, mechanical properties and thermal stability in CB/PE-RT and CBE/POE/PE-RT composite system. The results show that it produces a synergistic effect between POE and EVA, the addition of POE changes the differences of viscoelastic between PE-RT and EVA, so that EVA reaches percolation to form a continuous network structure in matrix, and CB disperses preferentially in EVA phase with low viscosity, higher polar, POE plays an inhibitory effect on migration of CB from EVA phase to PE-RT phase, then CB reaches percolation in EVA phase easily. Finally it forms a conductive network structure because of dual role of percolation. CB improves the crystallization property of PE-RT and thermal stability of CBE/POE/PE-RT composite system, and CB has little effects on the mechanical properties of CBE/POE/PE-RT composite system, to a certain extent, it solves the contradiction between conductivity and mechanical properties of filled-type conductivity systems. POE has a plasticizing effect on composite system, maintaining the advantages of PE-RT pipes that can be bent, expanding the application scope of plastic pipe.
2015, 32(5): 1330-1340.
doi: 10.13801/j.cnki.fhclxb.20150310.002
Abstract:
In order to investigate the effects of ultrasonic vibration on injection molding characteristics of fiber reinforce composites, by using a self-developed ultrasonic assisted injection molding visualization experimental device, visualization experiments under ultrasonic field effects were conducted on glass fiber (GF) reinforced polypropylene (PP) composites with different GF contents. Effects of ultrasonic power on filling flow behaviors of composite melts were observed and analyzed. In addition, the effects of ultrasonic power on fiber orientation of composites were also analyzed by metallographic observation of different parts of specimens. The results show that ultrasonic power affects the composites filling flow behaviors of injection modeling and the fiber orientation of products. While the fiber content of composites also has direct influences on the effects of ultrasonic vibration. When the fiber content is lower, the main reason which influences the filling flow ability of composites and fiber orientation is the effect of ultrasonic vibration on micromorphology of matrix materials; when the fiber content is higher, the main reason which influences the filling flow ability of composites and fiber orientation is the effect of ultrasonic vibration on fibers. The investigation results provide the basis for the development of ultrasonic assistant molding technology for composites.
In order to investigate the effects of ultrasonic vibration on injection molding characteristics of fiber reinforce composites, by using a self-developed ultrasonic assisted injection molding visualization experimental device, visualization experiments under ultrasonic field effects were conducted on glass fiber (GF) reinforced polypropylene (PP) composites with different GF contents. Effects of ultrasonic power on filling flow behaviors of composite melts were observed and analyzed. In addition, the effects of ultrasonic power on fiber orientation of composites were also analyzed by metallographic observation of different parts of specimens. The results show that ultrasonic power affects the composites filling flow behaviors of injection modeling and the fiber orientation of products. While the fiber content of composites also has direct influences on the effects of ultrasonic vibration. When the fiber content is lower, the main reason which influences the filling flow ability of composites and fiber orientation is the effect of ultrasonic vibration on micromorphology of matrix materials; when the fiber content is higher, the main reason which influences the filling flow ability of composites and fiber orientation is the effect of ultrasonic vibration on fibers. The investigation results provide the basis for the development of ultrasonic assistant molding technology for composites.
2015, 32(5): 1341-1348.
doi: 10.13801/j.cnki.fhclxb.20150302.003
Abstract:
In order to investigate the interface bonding behavior of shape memory alloy (SMA) filament reinforced epoxy composites, the interfacial bonding strength of SMA filament/epoxy was tested through single fiber pull-out test firstly. The effects of embedding depth on ultimate interfacial bonding strength and the debonding behavior were analyzed emphatically. Then, using ABAQUS finite element analyses method, the changing relationship of stress distribution versus time during the SMA filament pull-out process was simulated by the element based on surface cohesive behavior. Finally, for the defect of low interfacial bonding strength of SMA/epoxy composites, the method in which nano SiO2 were used to modify the surfaces of SMA filaments was proposed to improve the interfacial bonding strength of materials, and was verified by debonding test. The results reveal that with the embedding depth increasing from 1.0 cm to 1.5 cm and 2.0 cm, the ultimate debonding load increases observably, while the average interfacial bonding strength decreases gradually. When the embedding depth of fiber is 2.0 cm, ultimate debonding appears at 0.300 s. By using the method of coating nano SiO2 particles on SMA surfaces, the surface roughness of fibers can be enhanced, and then improves the ultimate debonding strength of SMA filaments reinforced epoxy composites effectively. The conclusions provide theoretic guidances for the application of SMA filaments in real engineering fields.
In order to investigate the interface bonding behavior of shape memory alloy (SMA) filament reinforced epoxy composites, the interfacial bonding strength of SMA filament/epoxy was tested through single fiber pull-out test firstly. The effects of embedding depth on ultimate interfacial bonding strength and the debonding behavior were analyzed emphatically. Then, using ABAQUS finite element analyses method, the changing relationship of stress distribution versus time during the SMA filament pull-out process was simulated by the element based on surface cohesive behavior. Finally, for the defect of low interfacial bonding strength of SMA/epoxy composites, the method in which nano SiO2 were used to modify the surfaces of SMA filaments was proposed to improve the interfacial bonding strength of materials, and was verified by debonding test. The results reveal that with the embedding depth increasing from 1.0 cm to 1.5 cm and 2.0 cm, the ultimate debonding load increases observably, while the average interfacial bonding strength decreases gradually. When the embedding depth of fiber is 2.0 cm, ultimate debonding appears at 0.300 s. By using the method of coating nano SiO2 particles on SMA surfaces, the surface roughness of fibers can be enhanced, and then improves the ultimate debonding strength of SMA filaments reinforced epoxy composites effectively. The conclusions provide theoretic guidances for the application of SMA filaments in real engineering fields.
2015, 32(5): 1349-1354.
doi: 10.13801/j.cnki.fhclxb.20150130.002
Abstract:
The combination of low-melting-point metal and polymer can not only yield electrically and thermally conductive composites with high performances, but also provides a new model to the investigation of multiphase and multi-ingredient polymer systems. In order to recognize the structure changes of low-melting-point metal liquid/polymer melt composite system under outfield effect systematically, the fibration phenomenon of Sn droplets in liquid Sn/molten polyethylene composite system under tensile condition were studied by optical microscope firstly. Then, the size of Sn particles in Sn/polyethylene composite systems at different tensile degrees was measured and the effect of tensile degree on the size of Sn particles was investigated. Finally, the fibration mechanism of Sn droplets was revealed. The results show that during the tensile process of liquid Sn/molten polyethylene composite system, the greater the Sn droplet diameter is, the earlier begins to fiberize. The diameter of fibrous Sn particles depends on the tensile degree of composite system, and the length depends on the volume of Sn droplet. The obtained conclusions can provide theoretic guidance to the preparation of metal/polymer composite with high performances.
The combination of low-melting-point metal and polymer can not only yield electrically and thermally conductive composites with high performances, but also provides a new model to the investigation of multiphase and multi-ingredient polymer systems. In order to recognize the structure changes of low-melting-point metal liquid/polymer melt composite system under outfield effect systematically, the fibration phenomenon of Sn droplets in liquid Sn/molten polyethylene composite system under tensile condition were studied by optical microscope firstly. Then, the size of Sn particles in Sn/polyethylene composite systems at different tensile degrees was measured and the effect of tensile degree on the size of Sn particles was investigated. Finally, the fibration mechanism of Sn droplets was revealed. The results show that during the tensile process of liquid Sn/molten polyethylene composite system, the greater the Sn droplet diameter is, the earlier begins to fiberize. The diameter of fibrous Sn particles depends on the tensile degree of composite system, and the length depends on the volume of Sn droplet. The obtained conclusions can provide theoretic guidance to the preparation of metal/polymer composite with high performances.
2015, 32(5): 1355-1360.
doi: 10.13801/j.cnki.fhclxb.20150109.001
Abstract:
In order to prepare high dielectric constant composites, pristine multi-walled carbon nanotubes (P-MWCNTs)/poly(vinylidene fluoride) (PVDF) composites and graphitized multi-walled carbon nanotubes (G-MWCNTs)/PVDF composites were prepared by injection molded method. Then G-MWCNTs and P-MWCNTs were characterized by Raman spectroscopy, and the fracture morphologies, mechanical properites and electrical properties of MWCNTs/PVDF composites were measured. The results show that G-MWCNTs have higher purity and crystallinity than those of P-MWCNTs. Two kinds of different MWCNTs both disperse in the PVDF matrix uniformly. The addition of MWCNTs affects the mechanical behaviors of PVDF significantly. The dielectric properties of MWCNTs/PVDF composites enhance with the content of MWCNTs increasing. Compared with P-MWCNTs, G-MWCNTs reduce the percolation threshold of the composites effectively. When the frequency is 100 Hz, the dielectric constant of pure PVDF is 7.0; when the content of P-MWCNTs is 5wt%, the dielectric constant of composites is 23.8; when the content of G-MWCNTs is 5wt%, the dielectric constant of composites reachs up to 105.0. The MWCNTs/PVDF composites prepared by injection molded method remain relatively low conductivity, thus resulting in a lower energy loss and having great significances for the charge storage applications.
In order to prepare high dielectric constant composites, pristine multi-walled carbon nanotubes (P-MWCNTs)/poly(vinylidene fluoride) (PVDF) composites and graphitized multi-walled carbon nanotubes (G-MWCNTs)/PVDF composites were prepared by injection molded method. Then G-MWCNTs and P-MWCNTs were characterized by Raman spectroscopy, and the fracture morphologies, mechanical properites and electrical properties of MWCNTs/PVDF composites were measured. The results show that G-MWCNTs have higher purity and crystallinity than those of P-MWCNTs. Two kinds of different MWCNTs both disperse in the PVDF matrix uniformly. The addition of MWCNTs affects the mechanical behaviors of PVDF significantly. The dielectric properties of MWCNTs/PVDF composites enhance with the content of MWCNTs increasing. Compared with P-MWCNTs, G-MWCNTs reduce the percolation threshold of the composites effectively. When the frequency is 100 Hz, the dielectric constant of pure PVDF is 7.0; when the content of P-MWCNTs is 5wt%, the dielectric constant of composites is 23.8; when the content of G-MWCNTs is 5wt%, the dielectric constant of composites reachs up to 105.0. The MWCNTs/PVDF composites prepared by injection molded method remain relatively low conductivity, thus resulting in a lower energy loss and having great significances for the charge storage applications.
2015, 32(5): 1361-1366.
doi: 10.13801/j.cnki.fhclxb.20150128.001
Abstract:
In order to investigate the spinnability and processing performance of the photocatalytic functional polypropylene (PP) fiber, SiO2 coated modified nano-TiO2 particles (SiO2@TiO2) were used as additive and PP was modified by blending firstly. Then, the extensional rheological properties of SiO2@TiO2/PP blend melts were tested by capillary rheometer, and the influences of SiO2@TiO2 on the properties of PP were studied by XRD and DSC. The results demonstrate that the SiO2@TiO2/PP blend melts belong to the fluids of extensional thinning type. With the increasing of temperature, both of the extensional stress and extensional viscosity of melts decrease; extensional viscosity increases with the increasing of additive amount, and extensional flow activation energy reduces with the increasing of extensional strain rate. The addition of SiO2@TiO2 does not change the crystalline structure of PP significantly, but enhance the performance of crystallization. When the content of SiO2@TiO2 is 4wt%, the crystallinity of the blend melt is 8.6% higher than that of pure PP. SiO2@TiO2 leads PP to form more compact crystal structure, which has important influences on the properties of materials.
In order to investigate the spinnability and processing performance of the photocatalytic functional polypropylene (PP) fiber, SiO2 coated modified nano-TiO2 particles (SiO2@TiO2) were used as additive and PP was modified by blending firstly. Then, the extensional rheological properties of SiO2@TiO2/PP blend melts were tested by capillary rheometer, and the influences of SiO2@TiO2 on the properties of PP were studied by XRD and DSC. The results demonstrate that the SiO2@TiO2/PP blend melts belong to the fluids of extensional thinning type. With the increasing of temperature, both of the extensional stress and extensional viscosity of melts decrease; extensional viscosity increases with the increasing of additive amount, and extensional flow activation energy reduces with the increasing of extensional strain rate. The addition of SiO2@TiO2 does not change the crystalline structure of PP significantly, but enhance the performance of crystallization. When the content of SiO2@TiO2 is 4wt%, the crystallinity of the blend melt is 8.6% higher than that of pure PP. SiO2@TiO2 leads PP to form more compact crystal structure, which has important influences on the properties of materials.
2015, 32(5): 1367-1373.
doi: 10.13801/j.cnki.fhclxb.20141218.001
Abstract:
The Al-30wt% Mg2Si composites were made by in-situ process and modified by adding rare earth element yittium (Y) with different contents, in order to investigate the effects of Y on microstructure and mechanical properties of composites and the refinement mechanism of Y on Al-30wt% Mg2Si composites. The results show that, the average grain size of primary phase Mg2Si decreases firstly then increases; but the strength, Brinell hardness and elongation increase firstly then decrease, when the addition amount of Y increases from 0 to 0.8wt%. With 0.6wt% addition amount of Y, refining effect of Al-30wt% Mg2Si composites is most obvious and the mechanical properties increase observably. Tensile strength increases from 145.5 MPa to 175.2 MPa, yield strength increases from 128.8 MPa to 152.0 MPa, Brinell hardness increases from HB101.4 to HB129.4, elongation increases from 2.4% to 3.3%.
The Al-30wt% Mg2Si composites were made by in-situ process and modified by adding rare earth element yittium (Y) with different contents, in order to investigate the effects of Y on microstructure and mechanical properties of composites and the refinement mechanism of Y on Al-30wt% Mg2Si composites. The results show that, the average grain size of primary phase Mg2Si decreases firstly then increases; but the strength, Brinell hardness and elongation increase firstly then decrease, when the addition amount of Y increases from 0 to 0.8wt%. With 0.6wt% addition amount of Y, refining effect of Al-30wt% Mg2Si composites is most obvious and the mechanical properties increase observably. Tensile strength increases from 145.5 MPa to 175.2 MPa, yield strength increases from 128.8 MPa to 152.0 MPa, Brinell hardness increases from HB101.4 to HB129.4, elongation increases from 2.4% to 3.3%.
2015, 32(5): 1374-1380.
doi: 10.13801/j.cnki.fhclxb.20141224.001
Abstract:
A new method of surface modification, "solid diffusion + rolling" was introduced, which means on the basis of studying surface modification method and technology of magnesium alloy sheet, solid diffusion method was applied to perform surface aluminizing-modification on AZ31 magnesium alloy sheet and obtain the Al/AZ31 magnesium matrix composite and by aid of finite element software LS-DYNA to simulate the cold rolling process to obtain optimum rolling technology conditions and rolling tests were performed. By means of the following appliances to test surface organization performance of material: XRD, SEM, metallographic microscope, Brinell hardness tester, reciprocating friction & wear tester and CorrTest corrosion electro-chemistry test system. The result indicates that the grain of Al/AZ31 magnesium matrix composite surface organization becomes much tinier and even due to surface deformation strengthening after rolling deformation, and a new phase MgAl2O4 is produced simultaneously making abrasion and corrosion resistance better which are manifested in surface Brinell hardness improving from HB61.4 to HB63.5, friction coefficient improving from 0.52 to 0.60, surface friction wear mass loss decreasing from 0.33 mg to 0.26 mg, self corrosion potential improving from -1.49 V to -1.38 V (surface corrosion resistance is improved significantly) and current density for self corrosion decreasing from 6.2×10-3 mA/cm2 to 7.0×10-4 mA/cm2. Abrasion resistance for Al/AZ31 magnesium matrix composite through "solid diffusion + rolling" is getting better as well as corrosion resistance.
A new method of surface modification, "solid diffusion + rolling" was introduced, which means on the basis of studying surface modification method and technology of magnesium alloy sheet, solid diffusion method was applied to perform surface aluminizing-modification on AZ31 magnesium alloy sheet and obtain the Al/AZ31 magnesium matrix composite and by aid of finite element software LS-DYNA to simulate the cold rolling process to obtain optimum rolling technology conditions and rolling tests were performed. By means of the following appliances to test surface organization performance of material: XRD, SEM, metallographic microscope, Brinell hardness tester, reciprocating friction & wear tester and CorrTest corrosion electro-chemistry test system. The result indicates that the grain of Al/AZ31 magnesium matrix composite surface organization becomes much tinier and even due to surface deformation strengthening after rolling deformation, and a new phase MgAl2O4 is produced simultaneously making abrasion and corrosion resistance better which are manifested in surface Brinell hardness improving from HB61.4 to HB63.5, friction coefficient improving from 0.52 to 0.60, surface friction wear mass loss decreasing from 0.33 mg to 0.26 mg, self corrosion potential improving from -1.49 V to -1.38 V (surface corrosion resistance is improved significantly) and current density for self corrosion decreasing from 6.2×10-3 mA/cm2 to 7.0×10-4 mA/cm2. Abrasion resistance for Al/AZ31 magnesium matrix composite through "solid diffusion + rolling" is getting better as well as corrosion resistance.
2015, 32(5): 1381-1389.
doi: 10.13801/j.cnki.fhclxb.20150303.004
Abstract:
La2O3-Y2O3-ZrO2(YSZ) composite ceramic powders with various La2O3 doping contents were prepared by chemical co-precipitation calcination method. High temperature phase stability, sintering resistance and thermo-physical properties of this composite ceramic powder were studied and also compared with those of the traditional YSZ ceramic powder in order to explore the possibility of La2O3-YSZ for thermal barrier coating material application. The crystal structure and phase composition of the ceramic powders were analyzed by XRD. The effect of La2O3 doping content on the high temperature phase stability of YSZ was investigated. SEM was used to analyze the microstructure of the sintered ceramics to investigate the effect of La2O3 doping on the sintering resistance of YSZ. Thermal diffusivity was tested by laser flash method and the thermal conductivity of material was obtained by calculation. The results indicate that YSZ and various La2O3 doping La2O3-YSZ are all composed of single non-equilibrium tetragonal phase ZrO2 (t'- ZrO2 ). After 100 h heat treatment at 1 400 ℃, the t'-ZrO2 in YSZ has completely transformed to cubic phase ZrO2 (c-ZrO2) and monoclinic phase ZrO2 (m-ZrO2). In the 0.4mol%-1.4mol% La2O3 doping range, La2O3-YSZ exhibits good phase stability than that of YSZ. YSZ doped by 1.0mol% La2O3 (1.0mol% La2O3-YSZ) does not generate m-ZrO2 after thermal treatment, showing good high temperature phase stability. In addition, 1.0mol% La2O3-YSZ has better sintering resistance and lower thermal conductivity in comparison with YSZ. In the temperature range from room temperature to 700 ℃, the thermal conductivity of 1.0mol% La2O3-YSZ is 1.90-2.17 W/(m·K) which is obviously lower than that of YSZ (2.13-2.33 W/(m·K)).
La2O3-Y2O3-ZrO2(YSZ) composite ceramic powders with various La2O3 doping contents were prepared by chemical co-precipitation calcination method. High temperature phase stability, sintering resistance and thermo-physical properties of this composite ceramic powder were studied and also compared with those of the traditional YSZ ceramic powder in order to explore the possibility of La2O3-YSZ for thermal barrier coating material application. The crystal structure and phase composition of the ceramic powders were analyzed by XRD. The effect of La2O3 doping content on the high temperature phase stability of YSZ was investigated. SEM was used to analyze the microstructure of the sintered ceramics to investigate the effect of La2O3 doping on the sintering resistance of YSZ. Thermal diffusivity was tested by laser flash method and the thermal conductivity of material was obtained by calculation. The results indicate that YSZ and various La2O3 doping La2O3-YSZ are all composed of single non-equilibrium tetragonal phase ZrO2 (t'- ZrO2 ). After 100 h heat treatment at 1 400 ℃, the t'-ZrO2 in YSZ has completely transformed to cubic phase ZrO2 (c-ZrO2) and monoclinic phase ZrO2 (m-ZrO2). In the 0.4mol%-1.4mol% La2O3 doping range, La2O3-YSZ exhibits good phase stability than that of YSZ. YSZ doped by 1.0mol% La2O3 (1.0mol% La2O3-YSZ) does not generate m-ZrO2 after thermal treatment, showing good high temperature phase stability. In addition, 1.0mol% La2O3-YSZ has better sintering resistance and lower thermal conductivity in comparison with YSZ. In the temperature range from room temperature to 700 ℃, the thermal conductivity of 1.0mol% La2O3-YSZ is 1.90-2.17 W/(m·K) which is obviously lower than that of YSZ (2.13-2.33 W/(m·K)).
2015, 32(5): 1390-1398.
doi: 10.13801/j.cnki.fhclxb.20150113.002
Abstract:
In order to obtain lithium ion battery cathode materials with high specific capacity, fast charging and discharging rate and excellent cycle performance, Co2+ doped graphene/LiFePO4 composite cathode materials for lithium battery (graphene/LiCo0.03Fe0.97PO4) were synthesized by using a sol-gel in-situ carbothermal reduction treatment. The structure and morphology characterization results show that graphene/LiCo0.03Fe0.97PO4 composites form 3D conducting network structure. The particles grow homogeneously in graphene sheets with the diameters of about 200 nm. The electrochemical test results show that graphene/LiCo0.03Fe0.97PO4 composites exhibit high reversible specific capacity and superior cycle rate performance with the first discharge specific capacity of 159 mA·h·g-1 at 0.1 C (2.0-4.0 V charge-discharge) and 74 mA·h·g-1 at 10.0 C of the first discharge. The specific capacity retention is 99.7% after 100 cycles at 0.5 C. The enhanced electrochemical property of graphene/LiCo0.03Fe0.97PO4 composites is attributed to the synergistic effect of Co2+ doping and graphene-modification.
In order to obtain lithium ion battery cathode materials with high specific capacity, fast charging and discharging rate and excellent cycle performance, Co2+ doped graphene/LiFePO4 composite cathode materials for lithium battery (graphene/LiCo0.03Fe0.97PO4) were synthesized by using a sol-gel in-situ carbothermal reduction treatment. The structure and morphology characterization results show that graphene/LiCo0.03Fe0.97PO4 composites form 3D conducting network structure. The particles grow homogeneously in graphene sheets with the diameters of about 200 nm. The electrochemical test results show that graphene/LiCo0.03Fe0.97PO4 composites exhibit high reversible specific capacity and superior cycle rate performance with the first discharge specific capacity of 159 mA·h·g-1 at 0.1 C (2.0-4.0 V charge-discharge) and 74 mA·h·g-1 at 10.0 C of the first discharge. The specific capacity retention is 99.7% after 100 cycles at 0.5 C. The enhanced electrochemical property of graphene/LiCo0.03Fe0.97PO4 composites is attributed to the synergistic effect of Co2+ doping and graphene-modification.
2015, 32(5): 1399-1407.
doi: 10.13801/j.cnki.fhclxb.20150123.001
Abstract:
In order to investigate the high temperature creep properties of nanoparticle reinforced aluminum matrix composites, the nano Al2O3/6063Al composites with different Al2O3 volume fractions (5%, 7%) were fabricated by in-situ synthesis technology via 6063Al-Al2(SO4)3 system assisted by ultrasonic chemistry. The high temperature creep tensile test was used to test the high temperature creep property of the prepared composites. XRD, OM, SEM and TEM were used to analyze micromorphology of the composites. The results show that with the help of the high-intensity ultrasoniy, the prepared Al2O3 reinforced particles mainly exhibit spherical or nearly hexagon shape with the size range from 20 to 100 nm, where the size refinement and dispersion uniformity of reinforced particles are elevated significantly. The apparent stress exponent, apparent activation energy and threshold stress value of nano Al2O3/6063Al composites increase gradually with the volume fraction increasing of reinforcement, and greatly compared with those of the corresponding matrix. The nano Al2O3/6063Al composites exhibit a significant improvement in creep resistance. The true stress exponent of nano Al2O3/6063Al composites is 8 and indicates that the creep mechanism of composites is in accordant to the substructure invariant model, i.e., controlled by the lattice diffusion. The high temperature fracture surface morphology of the nano Al2O3/6063Al composites indicates a brittle fracture of the composite and exhibits transcrystalline fracture under high stress condition, intergranular fracture and voids at grain boundary under low stress condition. The main strengthening mechanisms of nano Al2O3/6063 Al composites are dislocation strengthening and dispersion strengthening.
In order to investigate the high temperature creep properties of nanoparticle reinforced aluminum matrix composites, the nano Al2O3/6063Al composites with different Al2O3 volume fractions (5%, 7%) were fabricated by in-situ synthesis technology via 6063Al-Al2(SO4)3 system assisted by ultrasonic chemistry. The high temperature creep tensile test was used to test the high temperature creep property of the prepared composites. XRD, OM, SEM and TEM were used to analyze micromorphology of the composites. The results show that with the help of the high-intensity ultrasoniy, the prepared Al2O3 reinforced particles mainly exhibit spherical or nearly hexagon shape with the size range from 20 to 100 nm, where the size refinement and dispersion uniformity of reinforced particles are elevated significantly. The apparent stress exponent, apparent activation energy and threshold stress value of nano Al2O3/6063Al composites increase gradually with the volume fraction increasing of reinforcement, and greatly compared with those of the corresponding matrix. The nano Al2O3/6063Al composites exhibit a significant improvement in creep resistance. The true stress exponent of nano Al2O3/6063Al composites is 8 and indicates that the creep mechanism of composites is in accordant to the substructure invariant model, i.e., controlled by the lattice diffusion. The high temperature fracture surface morphology of the nano Al2O3/6063Al composites indicates a brittle fracture of the composite and exhibits transcrystalline fracture under high stress condition, intergranular fracture and voids at grain boundary under low stress condition. The main strengthening mechanisms of nano Al2O3/6063 Al composites are dislocation strengthening and dispersion strengthening.
2015, 32(5): 1408-1413.
doi: 10.13801/j.cnki.fhclxb.20150120.003
Abstract:
SiC reinforced graphite composites were prepared with natural flake graphite as raw materials and SiC particles as reinforcement phase by hot-pressing sintering process. The effects of SiC contents on microstructures, mechanical properties and friction behavior of SiC reinforced graphite composites were analyzed. The results show that the SiC particles are uniformly distributed in graphite matrix, greatly reducing the porosity of matrix. With the increasing of SiC content, relative density and bending strength of SiC reinforced graphite composites increase, and the open porosity falls significantly. The relative density and flexural strength of composites with 40vol% SiC reach 94.2% and 146 MPa due to the formation of SiC network backbone structure in SiC reinforced graphite composites, 11.8% and 147% larger than those of commodity high-strength pure graphite materials. Matrix graphite keeps the layered structure. The friction coefficients of SiC reinforced graphite composites increase slightly with the content of SiC increasing, which keep the same friction coefficient of pure graphite material when the content of SiC is no more than 40vol%, which shows good friction properties.
SiC reinforced graphite composites were prepared with natural flake graphite as raw materials and SiC particles as reinforcement phase by hot-pressing sintering process. The effects of SiC contents on microstructures, mechanical properties and friction behavior of SiC reinforced graphite composites were analyzed. The results show that the SiC particles are uniformly distributed in graphite matrix, greatly reducing the porosity of matrix. With the increasing of SiC content, relative density and bending strength of SiC reinforced graphite composites increase, and the open porosity falls significantly. The relative density and flexural strength of composites with 40vol% SiC reach 94.2% and 146 MPa due to the formation of SiC network backbone structure in SiC reinforced graphite composites, 11.8% and 147% larger than those of commodity high-strength pure graphite materials. Matrix graphite keeps the layered structure. The friction coefficients of SiC reinforced graphite composites increase slightly with the content of SiC increasing, which keep the same friction coefficient of pure graphite material when the content of SiC is no more than 40vol%, which shows good friction properties.
2015, 32(5): 1414-1419.
doi: 10.13801/j.cnki.fhclxb.20141118.008
Abstract:
The numerical analysis of adhesive anchorage system for carbon fiber reinforced plastics (CFRP) tendon was conducted, of which including influence of different friction coefficients between anchor wall and anchorage agglomerant, influence of different cone angles and with or without straight transition section in front of anchorage and end blocking constraint to the stress state of tendons. The reason of tendons that fail near the front end of the anchorage was found out, relevant strength analysis method and anchorage improvement methods were proposed, the effectiveness of the method were verified by test results. The analysis results show that radial extrusion stress peak values of tendons at 0.7 friction coefficient are 45.01% of the radial extrusion stress peak values at 0.3 friction coefficient. Radial extrusion stress peak values of CFRP tendons at anchorage cone section decrease with the increase of cone angles, while shear stress peak values gradually increase. The addition of straight transition section at cone section ends can relieve radial extrusion stress and shear stress peak values of tendons. Mitigation coefficients are 76.78% and 52.90%, respectively. The existence of end blocking constraint leads an obviously stress concentration phenomenon at the front end of anchorage, which results in the failure of tendon near the front end of anchorage.
The numerical analysis of adhesive anchorage system for carbon fiber reinforced plastics (CFRP) tendon was conducted, of which including influence of different friction coefficients between anchor wall and anchorage agglomerant, influence of different cone angles and with or without straight transition section in front of anchorage and end blocking constraint to the stress state of tendons. The reason of tendons that fail near the front end of the anchorage was found out, relevant strength analysis method and anchorage improvement methods were proposed, the effectiveness of the method were verified by test results. The analysis results show that radial extrusion stress peak values of tendons at 0.7 friction coefficient are 45.01% of the radial extrusion stress peak values at 0.3 friction coefficient. Radial extrusion stress peak values of CFRP tendons at anchorage cone section decrease with the increase of cone angles, while shear stress peak values gradually increase. The addition of straight transition section at cone section ends can relieve radial extrusion stress and shear stress peak values of tendons. Mitigation coefficients are 76.78% and 52.90%, respectively. The existence of end blocking constraint leads an obviously stress concentration phenomenon at the front end of anchorage, which results in the failure of tendon near the front end of anchorage.
2015, 32(5): 1420-1427.
doi: 10.13801/j.cnki.fhclxb.20150515.002
Abstract:
Based on a brief survey of the test methods for load in composite multi-bolt joints, an instrumented bolt for load vector plan without prearranged installation angle demand and with the capability of load direction measurement is presented to overcome the shortcoming of the existed instrumented bolt that it must be installed according to provided load direction. The material selection, stickup scheme of strain gauges and slot dimensions of the instrumented bolt for load vector were designed, from which the instrumented bolt for load vector was further manufactured. The linearity and repeatability of test results of instrumented bolt for load vector, the effect of the installation angle on the test results and the load direction measurements were experimentally investigated with a single-lap, single-bolt composite joint. The test outcomes show the presented instrumented bolt for load vector satisfies the technical requirements for measuring load distribution of bolts in engineering, which further verifies the suitability of the proposed instrumented bolt for load vector.
Based on a brief survey of the test methods for load in composite multi-bolt joints, an instrumented bolt for load vector plan without prearranged installation angle demand and with the capability of load direction measurement is presented to overcome the shortcoming of the existed instrumented bolt that it must be installed according to provided load direction. The material selection, stickup scheme of strain gauges and slot dimensions of the instrumented bolt for load vector were designed, from which the instrumented bolt for load vector was further manufactured. The linearity and repeatability of test results of instrumented bolt for load vector, the effect of the installation angle on the test results and the load direction measurements were experimentally investigated with a single-lap, single-bolt composite joint. The test outcomes show the presented instrumented bolt for load vector satisfies the technical requirements for measuring load distribution of bolts in engineering, which further verifies the suitability of the proposed instrumented bolt for load vector.
2015, 32(5): 1428-1435.
doi: 10.13801/j.cnki.fhclxb.20150105.002
Abstract:
In-plane shear testing program was designed for mullite fiber reinforced aerogel composites based on the V-notched two-rail shear method. In-plane shear and bending property tests were conducted at room temperature. Displacement and strain fields on the specimen surface were measured by approach of digital image correlation method, and mechanical behaviors and failure modes were analyzed. Results show that the testing program can obtain uniform shear strain field in the test area, so it is suitable for the in-plane shear property tests of mullite fiber reinforced aerogel composites. The in-plane shear modulus and strength obtained by tests are 248 MPa and 0.95 MPa, respectively; the bending modulus and strength are 294 MPa and 2.08 MPa, respectively. Under the in-plane shear load, the cracks initiate near the notch tips and propagate along the path between the two notches. According to the characteristic of bending normal strain distribution, it is found that the neutral plane is not coincide with the geometric symmetry plane. The characteristic of different modulus in tension and compression is validated. The neutral plane position measured by the digital image correlation method is in approximate agreement with the theoretically calculated position, and the relative error is about 10%.
In-plane shear testing program was designed for mullite fiber reinforced aerogel composites based on the V-notched two-rail shear method. In-plane shear and bending property tests were conducted at room temperature. Displacement and strain fields on the specimen surface were measured by approach of digital image correlation method, and mechanical behaviors and failure modes were analyzed. Results show that the testing program can obtain uniform shear strain field in the test area, so it is suitable for the in-plane shear property tests of mullite fiber reinforced aerogel composites. The in-plane shear modulus and strength obtained by tests are 248 MPa and 0.95 MPa, respectively; the bending modulus and strength are 294 MPa and 2.08 MPa, respectively. Under the in-plane shear load, the cracks initiate near the notch tips and propagate along the path between the two notches. According to the characteristic of bending normal strain distribution, it is found that the neutral plane is not coincide with the geometric symmetry plane. The characteristic of different modulus in tension and compression is validated. The neutral plane position measured by the digital image correlation method is in approximate agreement with the theoretically calculated position, and the relative error is about 10%.
2015, 32(5): 1436-1444.
doi: 10.13801/j.cnki.fhclxb.20150401.001
Abstract:
In order to accurately test the compression property of carbon fiber (CF), sample preparation method and test fixture were designed based on carbon fiber multifilament with impregnation curing, and a measuring method for compression property of carbon fiber multifilament was established. The compression properties of Toray T700SC and other carbon fibers were tested using the established method. The influences of sample preparation conditions, test conditions and material type on compression strength and failure mode of carbon fiber multifilament were investigated. The considered factors include resin content of multifilament, tension of multifilament during impregnation curing, pre-loading, testing length, resin matrix and fiber types. The results show that the established method is easy operation and has low dispersibility of test results. Except pre-loading, other factors have obvious effects on the testing process and result. For 30%-35% resin content of sample(mass percent of resin), 10-15 N tension of multifilament impregnation, and 1.5 mm testing length, epoxy impregnated curing T700SC carbon fiber multifilament has the highest testing result of compression strength, and the optimized test conditions are also applicable to the compression strength test of other kinds of carbon fiber multifilament. The type of resin has significant impact on the compression strength of multifilament.
In order to accurately test the compression property of carbon fiber (CF), sample preparation method and test fixture were designed based on carbon fiber multifilament with impregnation curing, and a measuring method for compression property of carbon fiber multifilament was established. The compression properties of Toray T700SC and other carbon fibers were tested using the established method. The influences of sample preparation conditions, test conditions and material type on compression strength and failure mode of carbon fiber multifilament were investigated. The considered factors include resin content of multifilament, tension of multifilament during impregnation curing, pre-loading, testing length, resin matrix and fiber types. The results show that the established method is easy operation and has low dispersibility of test results. Except pre-loading, other factors have obvious effects on the testing process and result. For 30%-35% resin content of sample(mass percent of resin), 10-15 N tension of multifilament impregnation, and 1.5 mm testing length, epoxy impregnated curing T700SC carbon fiber multifilament has the highest testing result of compression strength, and the optimized test conditions are also applicable to the compression strength test of other kinds of carbon fiber multifilament. The type of resin has significant impact on the compression strength of multifilament.
2015, 32(5): 1445-1452.
doi: 10.13801/j.cnki.fhclxb.20141103.003
Abstract:
In order to improve the ability to resist defects of lattice materials, soft material layers were adhered to the surfaces of cell edges of regular hexagon, Kagome and regular triangle lattice materials, and hierarchical lattice materials were prepared. Then, for the edge waviness defect type, the imperfection sensitivities of the in-plane moduli and mechanical performances of lattice materials were investigated by analytic method, and the theoretical values were verified by numerical simulations. The results indicate that by choosing appropriate adhesive soft material layer and geometric parameters can make the resist ability of hierarchical lattice materials to defect higher than that of classic lattice materials, and show relative low imperfection sensitivities. Meanwhile, on condition of the relative density remains unchanged, the mechanical performances of hierarchical lattice materials have a great enhancement compared with that of classic lattice materials. The investigation conclusions provide theoretical basis for the design and manufacture of new lattice materials which have anti-defect abilities.
In order to improve the ability to resist defects of lattice materials, soft material layers were adhered to the surfaces of cell edges of regular hexagon, Kagome and regular triangle lattice materials, and hierarchical lattice materials were prepared. Then, for the edge waviness defect type, the imperfection sensitivities of the in-plane moduli and mechanical performances of lattice materials were investigated by analytic method, and the theoretical values were verified by numerical simulations. The results indicate that by choosing appropriate adhesive soft material layer and geometric parameters can make the resist ability of hierarchical lattice materials to defect higher than that of classic lattice materials, and show relative low imperfection sensitivities. Meanwhile, on condition of the relative density remains unchanged, the mechanical performances of hierarchical lattice materials have a great enhancement compared with that of classic lattice materials. The investigation conclusions provide theoretical basis for the design and manufacture of new lattice materials which have anti-defect abilities.
2015, 32(5): 1453-1460.
doi: 10.13801/j.cnki.fhclxb.20141105.001
Abstract:
In order to improve the dynamics property of composite structures significantly, a new co-cured composite structure with multilayer damping membranes embedded was proposed firstly, and the specimens of the embedded medium-temperature co-cured multilayer damping membranes composites were manufactured according to the curing process curves of glass fiber/epoxy (5231/EW180B) prepreg. Then, the finite element numerical simulation method based on modal strain energy was explored to investigate the dynamics property of the structure. Finally, the results were compared with the experimental data of modal analysis, and the variation relationships of modal parameters of co-cured composite structure with multilayer damping membranes embedded versus the thickness, number, location and distribution of damping layers were obtained. The results indicate that the composite structure with multilayer damping membranes embedded can enhance the first order modal loss factor of whole structure greatly. The research results lay the foundation of the further investigation of designing theory and manufacturing technology of composite structure with lightweight and high damping.
In order to improve the dynamics property of composite structures significantly, a new co-cured composite structure with multilayer damping membranes embedded was proposed firstly, and the specimens of the embedded medium-temperature co-cured multilayer damping membranes composites were manufactured according to the curing process curves of glass fiber/epoxy (5231/EW180B) prepreg. Then, the finite element numerical simulation method based on modal strain energy was explored to investigate the dynamics property of the structure. Finally, the results were compared with the experimental data of modal analysis, and the variation relationships of modal parameters of co-cured composite structure with multilayer damping membranes embedded versus the thickness, number, location and distribution of damping layers were obtained. The results indicate that the composite structure with multilayer damping membranes embedded can enhance the first order modal loss factor of whole structure greatly. The research results lay the foundation of the further investigation of designing theory and manufacturing technology of composite structure with lightweight and high damping.
2015, 32(5): 1461-1468.
doi: 10.13801/j.cnki.fhclxb.20141204.005
Abstract:
Fly ash cenosphere(FAC)/AZ91D Mg alloy composites were prepared using stir casting method. The high-temperature compression deformation behavior of FAC/AZ91D Mg alloy composites was studied, the influences of compression deformation temperature and strain rate on compression deformation behavior of FAC/AZ91D Mg alloy composites were analyzed, and the thermal deformation activation energy was calculated. The results show that the high-temperature compression true stress-true strain curves of FAC/AZ91D Mg alloy composites can be divided into four stages: elastic deformation, work hardening, peak stress and steady-state flow stage. At the same strain rate, the peak stress and steady-state flow stress of FAC/AZ91D Mg alloy composites decrease with increasing compression deformation temperature; at same compression deformation temperature, the flow stress increases with increasing strain rate. At the same strain rate or the same compression deformation temperature, the hot deformation activation energy of FAC/AZ91D Mg alloy composites increases with the increase of the compression strain rate or the compression deformation temperature. The thermal compression behavior can be described with Arrhenius relationship with hyperbolic sine function form. Both compression deformation temperature and the strain rate have important effects on the high-temperature compression structure of FAC/AZ91D Mg alloy composites. Increasing the compression deformation temperature or the strain rate can accelerate the process of dynamic recrystallization.
Fly ash cenosphere(FAC)/AZ91D Mg alloy composites were prepared using stir casting method. The high-temperature compression deformation behavior of FAC/AZ91D Mg alloy composites was studied, the influences of compression deformation temperature and strain rate on compression deformation behavior of FAC/AZ91D Mg alloy composites were analyzed, and the thermal deformation activation energy was calculated. The results show that the high-temperature compression true stress-true strain curves of FAC/AZ91D Mg alloy composites can be divided into four stages: elastic deformation, work hardening, peak stress and steady-state flow stage. At the same strain rate, the peak stress and steady-state flow stress of FAC/AZ91D Mg alloy composites decrease with increasing compression deformation temperature; at same compression deformation temperature, the flow stress increases with increasing strain rate. At the same strain rate or the same compression deformation temperature, the hot deformation activation energy of FAC/AZ91D Mg alloy composites increases with the increase of the compression strain rate or the compression deformation temperature. The thermal compression behavior can be described with Arrhenius relationship with hyperbolic sine function form. Both compression deformation temperature and the strain rate have important effects on the high-temperature compression structure of FAC/AZ91D Mg alloy composites. Increasing the compression deformation temperature or the strain rate can accelerate the process of dynamic recrystallization.
2015, 32(5): 1469-1479.
doi: 10.13801/j.cnki.fhclxb.20141230.002
Abstract:
In order to reveal the relationship between the cutting temperature in machining carbon fiber reinforced plastic (CFRP) and the cutting factors, orthogonally free machining tests on CFRP unidirectional laminates were conducted. The cutting temperature was measured using OMEGA-0.05 mm K type high sensitive thermocouple. Discussions were made about the effects of cutting parameters, geometric parameters of tools and material parameters on cutting temperature. The results show that cutting speed, cutting thickness, relief angle of tool and blunt radius, in the sequence of descending, have great influence on cutting temperature. The influence of cutting parameters on the temperature is not affected by the fiber orientation angle. Unlike metal materials, the cutting temperature is greatly influenced by CFRP fiber orientation angle. The cutting temperature cut along fiber orientation is significantly higher than that opposite fiber orientation. The maximum cutting temperature is present to the fiber orientation angle of 90°, and the cutting temperature at the fiber orientation angle of 90° is 2 times of that at the fiber orientation angle of 0°. The spring back of CFRP has great influence on the contact condition between the tool flank and the machined surface, which will affect the cutting temperature eventually. This has exacerbated the anisotropy of the cutting temperature. Moreover, the heat in the third deformation zone has prominent effect on cutting temperature. CFRP has a narrow cutting temperature range, maximum cutting temperature is about 300 ℃, which will make cutting quality more sensitive to temperature changes.
In order to reveal the relationship between the cutting temperature in machining carbon fiber reinforced plastic (CFRP) and the cutting factors, orthogonally free machining tests on CFRP unidirectional laminates were conducted. The cutting temperature was measured using OMEGA-0.05 mm K type high sensitive thermocouple. Discussions were made about the effects of cutting parameters, geometric parameters of tools and material parameters on cutting temperature. The results show that cutting speed, cutting thickness, relief angle of tool and blunt radius, in the sequence of descending, have great influence on cutting temperature. The influence of cutting parameters on the temperature is not affected by the fiber orientation angle. Unlike metal materials, the cutting temperature is greatly influenced by CFRP fiber orientation angle. The cutting temperature cut along fiber orientation is significantly higher than that opposite fiber orientation. The maximum cutting temperature is present to the fiber orientation angle of 90°, and the cutting temperature at the fiber orientation angle of 90° is 2 times of that at the fiber orientation angle of 0°. The spring back of CFRP has great influence on the contact condition between the tool flank and the machined surface, which will affect the cutting temperature eventually. This has exacerbated the anisotropy of the cutting temperature. Moreover, the heat in the third deformation zone has prominent effect on cutting temperature. CFRP has a narrow cutting temperature range, maximum cutting temperature is about 300 ℃, which will make cutting quality more sensitive to temperature changes.
2015, 32(5): 1480-1486.
doi: 10.13801/j.cnki.fhclxb.20150113.003
Abstract:
The hybrid system is prepared basing on nitrile butadiene rubber (NBR) matrix with addition of 2,2'-methylenebis (4-methyl-6-tert-butyl-phenol)(AO-2246) hindered phenol. The flake graphite powder (FGP) was introduced into the system in order to study its impact on the dynamic mechanic property of the blends. The dynamic mechanic property of FGP/AO-2246-NBR blends was studied by DMA, FTIR, SEM, etc. The results suggest that after the addition of FGP into AO-2246-NBR blends, the tangent of loss angle, dynamic storage modulus and loss modulus all present a trend which increase and then decrease when the content of FGP increases. By the time the content of FGP reaches its critical value(mass ratio: about 10%), the dynamic mechanic property such as the tangent of loss angle, dynamic storage modulus and loss modulus would have better performance. According to the FTIR analysis, hydrogen bonding effect is not the key factor to the dynamic mechanic property of ternary blends system. It has great correlation to the characteristics of FGP itself as well as the formation of microstructure which results from the interaction between FGP and AO-2246-NBR blends.
The hybrid system is prepared basing on nitrile butadiene rubber (NBR) matrix with addition of 2,2'-methylenebis (4-methyl-6-tert-butyl-phenol)(AO-2246) hindered phenol. The flake graphite powder (FGP) was introduced into the system in order to study its impact on the dynamic mechanic property of the blends. The dynamic mechanic property of FGP/AO-2246-NBR blends was studied by DMA, FTIR, SEM, etc. The results suggest that after the addition of FGP into AO-2246-NBR blends, the tangent of loss angle, dynamic storage modulus and loss modulus all present a trend which increase and then decrease when the content of FGP increases. By the time the content of FGP reaches its critical value(mass ratio: about 10%), the dynamic mechanic property such as the tangent of loss angle, dynamic storage modulus and loss modulus would have better performance. According to the FTIR analysis, hydrogen bonding effect is not the key factor to the dynamic mechanic property of ternary blends system. It has great correlation to the characteristics of FGP itself as well as the formation of microstructure which results from the interaction between FGP and AO-2246-NBR blends.
2015, 32(5): 1487-1495.
doi: 10.13801/j.cnki.fhclxb.20150302.001
Abstract:
In the process of wing design, equivalent finite element model (EFEM) method was utilized for the optimization of wing structure with static and dynamic constraints. An structure optimization strategy with three steps, which convert a multivariable complex optimization problem to a series of simple optimization problems with a few design variables, was proposed for a composite wing of regional civil jet design. Firstly, the ratio of composite layers was optimized with displacement, static strength and flutter speed as constraints. Then each stiffened panel between ribs was optimized for minimizing structure weight and structure efficiency with the static strength and structure stability as constraints. Finally, the overall stiffness of the wing structure was optimized with displacement and flutter speed as constraints. The results show that the EFEM method is suitable for wing structure preliminary optimization for the advantage of rapid modeling and low computational cost. And the strategy with three steps in the structural optimization has higher efficiency.
In the process of wing design, equivalent finite element model (EFEM) method was utilized for the optimization of wing structure with static and dynamic constraints. An structure optimization strategy with three steps, which convert a multivariable complex optimization problem to a series of simple optimization problems with a few design variables, was proposed for a composite wing of regional civil jet design. Firstly, the ratio of composite layers was optimized with displacement, static strength and flutter speed as constraints. Then each stiffened panel between ribs was optimized for minimizing structure weight and structure efficiency with the static strength and structure stability as constraints. Finally, the overall stiffness of the wing structure was optimized with displacement and flutter speed as constraints. The results show that the EFEM method is suitable for wing structure preliminary optimization for the advantage of rapid modeling and low computational cost. And the strategy with three steps in the structural optimization has higher efficiency.
2015, 32(5): 1496-1502.
doi: 10.13801/j.cnki.fhclxb.20150303.002
Abstract:
2.5D stuffer warp reinforced composites were prepared by combining the three-dimensional weaving technology and resin transfer molding (RTM) process in which the carbon fiber is domestic manufactured with different sizing amounts. The weaving damage condition of warp, stuffer warp and weft in performs of different kinds of sizing amounts were investigated by using hairiness testing, multifilament yarns tensile tests and SEM. The results show that carbon fiber woven damage rates decrease as the sizing amount increase. The order of yarn damage rates in 2.5D stuffer warp reinforced composites is weft, warp, stuffer warp. Tensile property test results of composites show that the 2.5D stuffer warp reinforced composites achieve optimal performance when the sizing amount of domestic carbon fiber is come to 2.01%.
2.5D stuffer warp reinforced composites were prepared by combining the three-dimensional weaving technology and resin transfer molding (RTM) process in which the carbon fiber is domestic manufactured with different sizing amounts. The weaving damage condition of warp, stuffer warp and weft in performs of different kinds of sizing amounts were investigated by using hairiness testing, multifilament yarns tensile tests and SEM. The results show that carbon fiber woven damage rates decrease as the sizing amount increase. The order of yarn damage rates in 2.5D stuffer warp reinforced composites is weft, warp, stuffer warp. Tensile property test results of composites show that the 2.5D stuffer warp reinforced composites achieve optimal performance when the sizing amount of domestic carbon fiber is come to 2.01%.
2015, 32(5): 1503-1509.
doi: 10.13801/j.cnki.fhclxb.20141224.003
Abstract:
In order to investigate the microstructure variation of phenol liquefied wood carbon fibers caused by activating treatment by Na2HPO4, by using Na2HPO4 solution as the activator, the phenol liquefied cunninghamia lanceolata carbon fiber precusors were impregnated, dried and activating treated at different temperatures. The crystal structure, pore structure and surface chemical structure of activated carbon fibers were characterized. The results show that the yield of activated carbon fibers decreases gradually with the increasing of activating temperature. The crystal structure of activated carbon fibers belongs to graphite-like structure. With the increasing of activation temperature, the microcrystalline layer spacing d002 decreases, while plan size of graphene sheets Lc and Lc/d002 increase. When the activation temperature is 600 ℃ or 700 ℃, the micropore ratio is below 48vol%; when the activation temperature is 800 ℃ or 900 ℃, the micropore ratio is above 60vol%. The microporous pore size of activated carbon fibers mainly concentrates in the range of 0.5-1.6 nm, and the mesoporous pore size mainly distributes in the range of 2.0-4.0 nm. With the increasing of activation temperature, the specific surface area and pore volume of fibers gradually increase, and both reache the maximum at 900 ℃, the specific surface area is 1 306 m2/g in this case. C and O are the basic elements of activated carbon fibers. On the surfaces of fiber, a large proportion of carbon-containing groups are graphite carbon, and containing a small proportion of C-OH, C=O and -COOH. The investigation provides references for preparing new type activated carbon fibers and further ascertaining the interaction between activator and molecules of carbon fibers.
In order to investigate the microstructure variation of phenol liquefied wood carbon fibers caused by activating treatment by Na2HPO4, by using Na2HPO4 solution as the activator, the phenol liquefied cunninghamia lanceolata carbon fiber precusors were impregnated, dried and activating treated at different temperatures. The crystal structure, pore structure and surface chemical structure of activated carbon fibers were characterized. The results show that the yield of activated carbon fibers decreases gradually with the increasing of activating temperature. The crystal structure of activated carbon fibers belongs to graphite-like structure. With the increasing of activation temperature, the microcrystalline layer spacing d002 decreases, while plan size of graphene sheets Lc and Lc/d002 increase. When the activation temperature is 600 ℃ or 700 ℃, the micropore ratio is below 48vol%; when the activation temperature is 800 ℃ or 900 ℃, the micropore ratio is above 60vol%. The microporous pore size of activated carbon fibers mainly concentrates in the range of 0.5-1.6 nm, and the mesoporous pore size mainly distributes in the range of 2.0-4.0 nm. With the increasing of activation temperature, the specific surface area and pore volume of fibers gradually increase, and both reache the maximum at 900 ℃, the specific surface area is 1 306 m2/g in this case. C and O are the basic elements of activated carbon fibers. On the surfaces of fiber, a large proportion of carbon-containing groups are graphite carbon, and containing a small proportion of C-OH, C=O and -COOH. The investigation provides references for preparing new type activated carbon fibers and further ascertaining the interaction between activator and molecules of carbon fibers.
2015, 32(5): 1510-1516.
doi: 10.13801/j.cnki.fhclxb.20150120.001
Abstract:
In order to investigate the sensing properties of platinum-perfluorosulfonic acid (Pt-PFSA) composites, the response output voltage of Pt-PFSA composites under step excitation and sine wave excitation was measured firstly. Then, by means of chemical plating method, the platinum atomic was deposited on the two surfaces of Nafion cation exchange membranes manufactured by Nafion solution whose thickness was 0.4 mm. Finally, the effects of water content on the output voltage of Pt-PFSA composites were investigated, the sensing performances of Pt-PFSA composites under sine excitation were predicted and the sine excitation experiments of different frequencies were conducted. The results show that after the adoption of moisturizing treatment, the reduction of output voltage caused by water content change is lower than 5%. Under the step excitation signal, when the strain of Pt-PFSA composites is 0.1%, output voltage has time delay. The sensitivity coefficient expression of Pt-PFSA composites is given, and the sensitivity coefficient of composites is 3.555 8 mV/0.2% when the signal frequency of sine wave excitation is 5.9 Hz. The obtained experiment results agree well with the predictions. The research lay the foundation of the sensing performance model establishment for Pt-PFSA composites.
In order to investigate the sensing properties of platinum-perfluorosulfonic acid (Pt-PFSA) composites, the response output voltage of Pt-PFSA composites under step excitation and sine wave excitation was measured firstly. Then, by means of chemical plating method, the platinum atomic was deposited on the two surfaces of Nafion cation exchange membranes manufactured by Nafion solution whose thickness was 0.4 mm. Finally, the effects of water content on the output voltage of Pt-PFSA composites were investigated, the sensing performances of Pt-PFSA composites under sine excitation were predicted and the sine excitation experiments of different frequencies were conducted. The results show that after the adoption of moisturizing treatment, the reduction of output voltage caused by water content change is lower than 5%. Under the step excitation signal, when the strain of Pt-PFSA composites is 0.1%, output voltage has time delay. The sensitivity coefficient expression of Pt-PFSA composites is given, and the sensitivity coefficient of composites is 3.555 8 mV/0.2% when the signal frequency of sine wave excitation is 5.9 Hz. The obtained experiment results agree well with the predictions. The research lay the foundation of the sensing performance model establishment for Pt-PFSA composites.
2015, 32(5): 1517-1526.
doi: 10.13801/j.cnki.fhclxb.20141230.001
Abstract:
In order to investigate the relationship between the vibration characteristics of chiral honeycomb composite with its band gap of vibration propagation, a discrete multi-degree of freedom inclusions-ligament vibration mechanical model of the material was established firstly. The model took elastic coupling between the local vibration of embedded inclusion and node ring connected by micro-structure ligaments as well as the evoked resonant eigenmodes into consideration. Then, the effects of coupling degree between micro-structural components and size parameters of micro-structural components on low frequency zone and high frequency zone of vibration absorbing band gaps of the materials were investigated emphatically, and the model was verified and analyzed by finite element method. The results show that except for flexible coated inclusions, the coupled evoked vibration, material and size parameters of node ring and ligaments all have obvious influences on natural vibration frequencies of chiral honeycomb composites, and thereby control the band gap position and band width. With the inner and outer elastic coupling degree node rings decreasing, the model frequency of inclusion will control the low-frequency zone of brand gap, and with the inclusion mass increasing, the frequency of low-frequency zone decreases. The high-frequency zone is characterized by the vibration of ligaments. When the inner and outer elastic coupling degree of node rings increasing, low-frequency zone of band gap is more sensitive to the eigenmodes of ligaments and framework, thus gap brand whose frequency is lower than that of inclusion eigenmode emerges. Whether the elastic coupling degree is strong or weak, when the thickness of ligament and node ring is reducing, the higher third-order frequency of the deformation of coating layer will be replaced by relatively lower frequency of ligament vibration. The conclusion can provide theoretical guidance for designing and research of chiral honeycomb type vibration isolation materials with small size and low-frequency wide band gap.
In order to investigate the relationship between the vibration characteristics of chiral honeycomb composite with its band gap of vibration propagation, a discrete multi-degree of freedom inclusions-ligament vibration mechanical model of the material was established firstly. The model took elastic coupling between the local vibration of embedded inclusion and node ring connected by micro-structure ligaments as well as the evoked resonant eigenmodes into consideration. Then, the effects of coupling degree between micro-structural components and size parameters of micro-structural components on low frequency zone and high frequency zone of vibration absorbing band gaps of the materials were investigated emphatically, and the model was verified and analyzed by finite element method. The results show that except for flexible coated inclusions, the coupled evoked vibration, material and size parameters of node ring and ligaments all have obvious influences on natural vibration frequencies of chiral honeycomb composites, and thereby control the band gap position and band width. With the inner and outer elastic coupling degree node rings decreasing, the model frequency of inclusion will control the low-frequency zone of brand gap, and with the inclusion mass increasing, the frequency of low-frequency zone decreases. The high-frequency zone is characterized by the vibration of ligaments. When the inner and outer elastic coupling degree of node rings increasing, low-frequency zone of band gap is more sensitive to the eigenmodes of ligaments and framework, thus gap brand whose frequency is lower than that of inclusion eigenmode emerges. Whether the elastic coupling degree is strong or weak, when the thickness of ligament and node ring is reducing, the higher third-order frequency of the deformation of coating layer will be replaced by relatively lower frequency of ligament vibration. The conclusion can provide theoretical guidance for designing and research of chiral honeycomb type vibration isolation materials with small size and low-frequency wide band gap.
2015, 32(5): 1527-1535.
doi: 10.13801/j.cnki.fhclxb.20150108.001
Abstract:
The surface roughness of biomaterial is one of the important factors which affect the cell behavior. In order to regulate the surface roughness of silk protein biomaterials and evaluate the effects of the surface roughness of material on cell growth behavior, Antheraea pernyi silk sericin (AS) solution was used as the template to induce the nucleation of hydroxyapatite (HAp) crystals by wet chemical coprecipitation method firstly, and therefore regulated the surface roughness of AS films. Then, the surface morphology, roughness and elements of HAp/AS composite films were characterized with SEM, roughometer, FTIR and EDX. Finally, the cell morphology and proliferation rate of bone mesenchymal stem cells (BMSCs) on the surface of HAp/AS composite films were detected with SEM and CellTiter 96® AQueous one solution cell proliferation assay reagent (MTS). The results show that the surface roughness of pure AS film is 0.15 μm. After mineralization for 1, 8 and 24 h, the surface roughness is 0.38, 0.46 and 1.20 μm, respectively. After mineralization of 24 h, some lobular compounds whose diameter is 30-80 nm can be observed on the surface of AS/HAp composite films. The resultant mineralized compound is HAp. HAp/AS films have good biocompatibility and the composite film whose surface roughness is 1.20 μm can promote the proliferation of BMSCs significantly. The roughness has important effect on attachment and morphology of BMSCs on the surfaces of HAp/AS films. Thus, the nucleation and growth of HAp crystal can be induced on the surfaces of biomacromolecules by the method of mineralization, there by regulate the surface roughness of materials, and investigate the cell behavior on the interface of materials.
The surface roughness of biomaterial is one of the important factors which affect the cell behavior. In order to regulate the surface roughness of silk protein biomaterials and evaluate the effects of the surface roughness of material on cell growth behavior, Antheraea pernyi silk sericin (AS) solution was used as the template to induce the nucleation of hydroxyapatite (HAp) crystals by wet chemical coprecipitation method firstly, and therefore regulated the surface roughness of AS films. Then, the surface morphology, roughness and elements of HAp/AS composite films were characterized with SEM, roughometer, FTIR and EDX. Finally, the cell morphology and proliferation rate of bone mesenchymal stem cells (BMSCs) on the surface of HAp/AS composite films were detected with SEM and CellTiter 96® AQueous one solution cell proliferation assay reagent (MTS). The results show that the surface roughness of pure AS film is 0.15 μm. After mineralization for 1, 8 and 24 h, the surface roughness is 0.38, 0.46 and 1.20 μm, respectively. After mineralization of 24 h, some lobular compounds whose diameter is 30-80 nm can be observed on the surface of AS/HAp composite films. The resultant mineralized compound is HAp. HAp/AS films have good biocompatibility and the composite film whose surface roughness is 1.20 μm can promote the proliferation of BMSCs significantly. The roughness has important effect on attachment and morphology of BMSCs on the surfaces of HAp/AS films. Thus, the nucleation and growth of HAp crystal can be induced on the surfaces of biomacromolecules by the method of mineralization, there by regulate the surface roughness of materials, and investigate the cell behavior on the interface of materials.
2015, 32(5): 1536-1546.
doi: 10.13801/j.cnki.fhclxb.20150428.005
Abstract:
In order to clarify the microstructure of cement paste under combined effect of carbonation and chloride salt, based on X-ray computed tomography (X-CT) and electron probe micro analyses (EPMA) technologies, the impact of chloride salt on carbonation rate of cement paste was investigated and element concentration distributions of Cl, S and Na in cement paste under the effect of carbonation were measured. The results show that the chloride salt can refine the pore structures of cement paste, improve the degree of density and slow down the carbonation rate of the cement paste with maintenance period of 28 d. The cracks in carbonation district of cement paste are easily generated under the effect of carbonation, and carbon dioxide gas diffuses into the inside of cement paste by those cracks to carbonize, leading to the uneven carbonation depth of cement paste. During carbonation process, Cl, S and Na elements migrate and concentrate to the non-carbonation area, the contents of elements which are distributed in initial state uniformly decease in carbonation area and increase in non-carbonated area, thus provide the scientific basis for durability design of concrete construction.
In order to clarify the microstructure of cement paste under combined effect of carbonation and chloride salt, based on X-ray computed tomography (X-CT) and electron probe micro analyses (EPMA) technologies, the impact of chloride salt on carbonation rate of cement paste was investigated and element concentration distributions of Cl, S and Na in cement paste under the effect of carbonation were measured. The results show that the chloride salt can refine the pore structures of cement paste, improve the degree of density and slow down the carbonation rate of the cement paste with maintenance period of 28 d. The cracks in carbonation district of cement paste are easily generated under the effect of carbonation, and carbon dioxide gas diffuses into the inside of cement paste by those cracks to carbonize, leading to the uneven carbonation depth of cement paste. During carbonation process, Cl, S and Na elements migrate and concentrate to the non-carbonation area, the contents of elements which are distributed in initial state uniformly decease in carbonation area and increase in non-carbonated area, thus provide the scientific basis for durability design of concrete construction.
