2017 Vol. 34, No. 7
2017, 34(7): 1401-1407.
doi: 10.13801/j.cnki.fhclxb.20161018.002
Abstract:
In order to prepare a light sound insulation composite, graphene oxide (GO) was used as the filler to prepare GO/nitrile butadiene rubber-poly(vinyl chloride) (GO/NBR-PVC) sound insulation composites by melt-blending process. The morphology, damping and mechanical properties of GO/NBR-PVC composites were measured by SEM, XRD, DMA and universal material testing machine. The sound insulation property was derived by the four-channel impedance tube system. The results show that GO is homogeneously dispersed in GO/NBR-PVC composites, and the elastic modulus, tensile strength and damping property of the composites improve obviously. Sound insulation experiment indicates that the sound insulation property of the GO/NBR-PVC composites increase, especially in the low frequency range. When GO mass fraction is 0.1%, 0.2%, 0.3%, 0.4%, the composite surface density shows little changes, the sound reduction index increase 0.8 dB, 1.1 dB, 1.5 dB, 1.2 dB, respectively. However, when heavy metal (HM) mass fraction is 30%, the surface density increases obviously, but the sound reduction index only increases 0.6 dB.
In order to prepare a light sound insulation composite, graphene oxide (GO) was used as the filler to prepare GO/nitrile butadiene rubber-poly(vinyl chloride) (GO/NBR-PVC) sound insulation composites by melt-blending process. The morphology, damping and mechanical properties of GO/NBR-PVC composites were measured by SEM, XRD, DMA and universal material testing machine. The sound insulation property was derived by the four-channel impedance tube system. The results show that GO is homogeneously dispersed in GO/NBR-PVC composites, and the elastic modulus, tensile strength and damping property of the composites improve obviously. Sound insulation experiment indicates that the sound insulation property of the GO/NBR-PVC composites increase, especially in the low frequency range. When GO mass fraction is 0.1%, 0.2%, 0.3%, 0.4%, the composite surface density shows little changes, the sound reduction index increase 0.8 dB, 1.1 dB, 1.5 dB, 1.2 dB, respectively. However, when heavy metal (HM) mass fraction is 30%, the surface density increases obviously, but the sound reduction index only increases 0.6 dB.
2017, 34(7): 1408-1415.
doi: 10.13801/j.cnki.fhclxb.20161020.001
Abstract:
Conductive rubber films filled with Ni coated carbon fibers (CF@Ni) were prepared by means of spraying process. The effects of Ni powder particle on the conductivity and flowability of conductive rubber were explored. The anti-folding properties of the conductive CF@Ni/rubber film and the adhesion strength between the film and aluminum alloy substrate were studied. The research results show that the resistivity of CF@Ni/conductive film dope with a small amount of spherical Ni powder is about 10-1 Ω·cm; with the increase of Ni powder, the resistivity of film does not change significantly while the mobility increases significantly; there is no significant decrease in the conductivity of the films when they have experienced 100 fold cycles with pressure of 0.2 MPa. The adhesion strength between CF@Ni/rubber coating film and aluminum alloy substrate is about 0.22 MPa. The conductive CF@Ni/rubber films have good electrical conductivity and anti-folding properties. CF@Ni plays a leading role in the conduction process, while spherical Ni powder plays the role of ‘lubrication’, improving the efficiency of spraying.
Conductive rubber films filled with Ni coated carbon fibers (CF@Ni) were prepared by means of spraying process. The effects of Ni powder particle on the conductivity and flowability of conductive rubber were explored. The anti-folding properties of the conductive CF@Ni/rubber film and the adhesion strength between the film and aluminum alloy substrate were studied. The research results show that the resistivity of CF@Ni/conductive film dope with a small amount of spherical Ni powder is about 10-1 Ω·cm; with the increase of Ni powder, the resistivity of film does not change significantly while the mobility increases significantly; there is no significant decrease in the conductivity of the films when they have experienced 100 fold cycles with pressure of 0.2 MPa. The adhesion strength between CF@Ni/rubber coating film and aluminum alloy substrate is about 0.22 MPa. The conductive CF@Ni/rubber films have good electrical conductivity and anti-folding properties. CF@Ni plays a leading role in the conduction process, while spherical Ni powder plays the role of ‘lubrication’, improving the efficiency of spraying.
2017, 34(7): 1416-1422.
doi: 10.13801/j.cnki.fhclxb.20160926.005
Abstract:
To obtain hydrogels with tough and self-healing properties, Ca2+/Agar-Polyacrylic acid(Ca2+/Agar-PAAc), Al3+/Agar-PAAc, Fe3+/Agar-PAAc composite double network hydrogels reinforced by ionic iron Ca2+, Al3+, Fe3+ cations were prepared by "one-pot" method. The enhancement function of metal ions Ca2+, Al3+, Fe3+, self-repairing properties, self-healing properties of reinforced hydrogels were studied. The tensile strength 320.7 kPa and elongation at break 1 130% of Fe3+/Agar-PAAc double network(DN) gels are 12 times and 9 times respectively those of Ca2+/Agar-PAAc DN gels. The tensile strength 320.7 kPa of Fe3+/Agar-PAAc DN gels is 5 times as large as that of Al3+/Agar-PAAc DN gels, elongation ratios of them are the same. Tensile with certain stain was applied to the sample to obtain damaged samples. The mechanical properties of Fe3+/Agar-PAAc DN hydrogels can be recovered to 100% of initial state after being soaked in ferric ion solution for 30 min. The mechanical properties of Fe3+/Agar-PAAc DN hydrogels can be recovered to 100% of initial state after being put in 50℃ condition for 15 min. By simply placing two hydrogel portions together and allowing enough self-healing time(48 h) for physical interactions to reestablish the network at the interface, the healed Fe3+/Agar-PAAc DN hydrogels can be stretched to 800% of initial length. The Fe3+/Agar-PAAc DN hydrogels reinforced by Fe3+ possess excellent mechanical properties and self-healing properties, without adding any chemicals and external stimuli, both networks possess self-healing properties.
To obtain hydrogels with tough and self-healing properties, Ca2+/Agar-Polyacrylic acid(Ca2+/Agar-PAAc), Al3+/Agar-PAAc, Fe3+/Agar-PAAc composite double network hydrogels reinforced by ionic iron Ca2+, Al3+, Fe3+ cations were prepared by "one-pot" method. The enhancement function of metal ions Ca2+, Al3+, Fe3+, self-repairing properties, self-healing properties of reinforced hydrogels were studied. The tensile strength 320.7 kPa and elongation at break 1 130% of Fe3+/Agar-PAAc double network(DN) gels are 12 times and 9 times respectively those of Ca2+/Agar-PAAc DN gels. The tensile strength 320.7 kPa of Fe3+/Agar-PAAc DN gels is 5 times as large as that of Al3+/Agar-PAAc DN gels, elongation ratios of them are the same. Tensile with certain stain was applied to the sample to obtain damaged samples. The mechanical properties of Fe3+/Agar-PAAc DN hydrogels can be recovered to 100% of initial state after being soaked in ferric ion solution for 30 min. The mechanical properties of Fe3+/Agar-PAAc DN hydrogels can be recovered to 100% of initial state after being put in 50℃ condition for 15 min. By simply placing two hydrogel portions together and allowing enough self-healing time(48 h) for physical interactions to reestablish the network at the interface, the healed Fe3+/Agar-PAAc DN hydrogels can be stretched to 800% of initial length. The Fe3+/Agar-PAAc DN hydrogels reinforced by Fe3+ possess excellent mechanical properties and self-healing properties, without adding any chemicals and external stimuli, both networks possess self-healing properties.
2017, 34(7): 1423-1429.
doi: 10.13801/j.cnki.fhclxb.20161024.006
Abstract:
The surface of SiO2 nano-particles was modified by γ-(trimethoxysily) propyl methacrylate (MPS) to prepare SiO2-MPS, and polymethylmethacrylate (PMMA) was grafted to the SiO2-MPS to prepare SiO2-MPS-PMMA via in situ polymerization. The nano-SiO2/PMMA transparent composites were prepared via melt blending method with PMMA and the pre-dispersed masterbatch which were prepared via melt blending method with PMMA and SiO2-PMS, SiO2-MPS-PMMA, respectively. Nano-SiO2 treated by MPS and PMMA were characterized and analyzed by FTIR and TG, and the structure of the nano-SiO2/PMMA composites was analyzed by SEM. The impact strength, contact angle and transmittance of the nano-SiO2/PMMA composites were also characterized. The results show that the chemical bonds are formed between nano-SiO2 and MPS, MPS and PMMA in SiO2-MPS/PMMA composites. The graft rate of MPS on the surface of nano-SiO2is 10.01%, while that of PMMA is 22.95%. In contrast, SiO2-MPS-PMMA has a better dispersion and lower aggregation in the PMMA. Compared to the pure PMMA, the impact strength and contact angle of the composites prepared by unmodified nano-SiO2 and organic modified nano-SiO2are slightly improved, and the transmittance reaches about 90%, up to 94.2%.
The surface of SiO2 nano-particles was modified by γ-(trimethoxysily) propyl methacrylate (MPS) to prepare SiO2-MPS, and polymethylmethacrylate (PMMA) was grafted to the SiO2-MPS to prepare SiO2-MPS-PMMA via in situ polymerization. The nano-SiO2/PMMA transparent composites were prepared via melt blending method with PMMA and the pre-dispersed masterbatch which were prepared via melt blending method with PMMA and SiO2-PMS, SiO2-MPS-PMMA, respectively. Nano-SiO2 treated by MPS and PMMA were characterized and analyzed by FTIR and TG, and the structure of the nano-SiO2/PMMA composites was analyzed by SEM. The impact strength, contact angle and transmittance of the nano-SiO2/PMMA composites were also characterized. The results show that the chemical bonds are formed between nano-SiO2 and MPS, MPS and PMMA in SiO2-MPS/PMMA composites. The graft rate of MPS on the surface of nano-SiO2is 10.01%, while that of PMMA is 22.95%. In contrast, SiO2-MPS-PMMA has a better dispersion and lower aggregation in the PMMA. Compared to the pure PMMA, the impact strength and contact angle of the composites prepared by unmodified nano-SiO2 and organic modified nano-SiO2are slightly improved, and the transmittance reaches about 90%, up to 94.2%.
2017, 34(7): 1430-1436.
doi: 10.13801/j.cnki.fhclxb.20170511.004
Abstract:
The effect of carbon nanotubes (CNTs), organic montmorillonite (OMMT), and Fe2O3 on the mechanical properties, thermal stability and hot aging resistance of perfluoropolyether (PFPE) rubbers were investigated. The thermal pyrolysis behaviors of pure PFPE rubber were analyzed by thermal decomposes method. The results indicate that dramatic increases in thermal stability are observed through the joined CNTs, OMMT and Fe2O3. Compared to pure PFPE rubber, the initial decomposition temperature and the 5% mass loss temperature of CNTs/PFPE rubber composite are 32.1℃ and 29.0℃ higher, respectively. The properties of Fe2O3/PFPE rubber composite after ageing at 200℃×72 h are obviously stabilized. The thermogravimetry and differential thermogravimetry curves of pure PFPE rubber move toward to high temperatures with increasing heating rate in air and N2. According to the Kissinger basic formula, the so-called activation energy of pure PFPE rubber is calculated to be 135.06 kJ/mol and 262.46 kJ/mol in air and N2, respectively.
The effect of carbon nanotubes (CNTs), organic montmorillonite (OMMT), and Fe2O3 on the mechanical properties, thermal stability and hot aging resistance of perfluoropolyether (PFPE) rubbers were investigated. The thermal pyrolysis behaviors of pure PFPE rubber were analyzed by thermal decomposes method. The results indicate that dramatic increases in thermal stability are observed through the joined CNTs, OMMT and Fe2O3. Compared to pure PFPE rubber, the initial decomposition temperature and the 5% mass loss temperature of CNTs/PFPE rubber composite are 32.1℃ and 29.0℃ higher, respectively. The properties of Fe2O3/PFPE rubber composite after ageing at 200℃×72 h are obviously stabilized. The thermogravimetry and differential thermogravimetry curves of pure PFPE rubber move toward to high temperatures with increasing heating rate in air and N2. According to the Kissinger basic formula, the so-called activation energy of pure PFPE rubber is calculated to be 135.06 kJ/mol and 262.46 kJ/mol in air and N2, respectively.
2017, 34(7): 1437-1442.
doi: 10.13801/j.cnki.fhclxb.20170112.005
Abstract:
To improve the ion conductivity and tensile strength of gel polymer electrolyte (GPE), a novel star-shaped polyhedral oligomericsilsesquioxane-polymethyl methacrylate (POSS-PMMA8) was successfully synthetized and introduced to the polymethyl methacrylate/polyacrylonitrile/polyvinylidene fluoride (PMMA-PAN-PVDF) matrix to obtain fibrous membrane M1 (POSS-PMMA8/PMMA-PAN-PVDF) by electrospinning. Membrane M1 was annealed at 120 ℃ to get membrane M2, or processed by hotpressing and pre-oxidizing to get membrane M3. Then the corresponding activated GPEs were prepared by soaking M1, M2 and M3 in liquid electrolyte. The morphologies, porosity, electrolyte uptake, and mechanical properties of these membranes (M1, M2 and M3), as well as the ion conductivity and electrochemical stability of their corresponding GPEs were fully investigated. The results show that, compared to M1, the tensile strength of M2 and ion conductivity of its GPE increase by 9.2% and 181.1%, respectively, and the electrochemical window of M2 and its GPE increases to 5.3 V; besides, the tensile strength of M3 and ion conductivity of its GPE increase by 193.7% and 20.2%, respectively, and the electrochemical window of M3 and its GPE increases to 5.5 V.
To improve the ion conductivity and tensile strength of gel polymer electrolyte (GPE), a novel star-shaped polyhedral oligomericsilsesquioxane-polymethyl methacrylate (POSS-PMMA8) was successfully synthetized and introduced to the polymethyl methacrylate/polyacrylonitrile/polyvinylidene fluoride (PMMA-PAN-PVDF) matrix to obtain fibrous membrane M1 (POSS-PMMA8/PMMA-PAN-PVDF) by electrospinning. Membrane M1 was annealed at 120 ℃ to get membrane M2, or processed by hotpressing and pre-oxidizing to get membrane M3. Then the corresponding activated GPEs were prepared by soaking M1, M2 and M3 in liquid electrolyte. The morphologies, porosity, electrolyte uptake, and mechanical properties of these membranes (M1, M2 and M3), as well as the ion conductivity and electrochemical stability of their corresponding GPEs were fully investigated. The results show that, compared to M1, the tensile strength of M2 and ion conductivity of its GPE increase by 9.2% and 181.1%, respectively, and the electrochemical window of M2 and its GPE increases to 5.3 V; besides, the tensile strength of M3 and ion conductivity of its GPE increase by 193.7% and 20.2%, respectively, and the electrochemical window of M3 and its GPE increases to 5.5 V.
2017, 34(7): 1443-1450.
doi: 10.13801/j.cnki.fhclxb.20161115.001
Abstract:
Aircraft structures of advanced composites are usually designed to post-buckling stage so that the most loading capability could be yielded. For the problem of post-buckling of composite stiffened plate structures, the self-developed program was introduced, which was embedded into software Patran as processing and post processing. The static buckling mode was calculated by this self-developed program, and then the mode was assumed as the initiation deflection for calculating post-buckling. The nonlinear equations were solved by increment iterative, arc-length control and energy convergence criterion. Introducing Tsai-Hill criterion of composite materials failure, the damage information of elements were judged and degraded. The self-developed program was verified by the compression test of composite stiffened plate. The post-buckling capacities of composite wing boxes were calculated and experimentally carried out in different cases such as loading and materials choosing, and the numerical results were in good agreement with the test data.
Aircraft structures of advanced composites are usually designed to post-buckling stage so that the most loading capability could be yielded. For the problem of post-buckling of composite stiffened plate structures, the self-developed program was introduced, which was embedded into software Patran as processing and post processing. The static buckling mode was calculated by this self-developed program, and then the mode was assumed as the initiation deflection for calculating post-buckling. The nonlinear equations were solved by increment iterative, arc-length control and energy convergence criterion. Introducing Tsai-Hill criterion of composite materials failure, the damage information of elements were judged and degraded. The self-developed program was verified by the compression test of composite stiffened plate. The post-buckling capacities of composite wing boxes were calculated and experimentally carried out in different cases such as loading and materials choosing, and the numerical results were in good agreement with the test data.
2017, 34(7): 1451-1461.
doi: 10.13801/j.cnki.fhclxb.20161024.002
Abstract:
Existing analytical models were modified for the analysis of a scarf repaired composite fabric laminate under unidirectional tension. Both analytical models for stepped-scarf repair and tapered-scarf repair were built, including the structures without extra plies, with one extra ply and with two extra plies. The algorithms were developed and accuracy degree was defined, to assess the accuracy of numerical calculation, implementing a user-friendly software program for the design and analysis of composite scarf repair under tensile load. By running the software, the shear stress/strain distribution in the adhesive layer can be presented, the failure level of repair patch and the base laminate can be evaluated and the ultimate failure load and failure modes can be predicted. T300/CYCOM-970 was used as adherent while METLBOND 1515-4M was used as adhesive. A series of corresponding experiments were conducted for validation. The results calculated by this software show a good agreement with experiment outcomes that the relative errors for stepped-scarf repair are less than 5.7% and the relative errors for tapered-scarf repair are less than 14.0%. This software provides an efficient and accurate preliminary design and analysis tool for the scarf repair of composite fabric laminates.
Existing analytical models were modified for the analysis of a scarf repaired composite fabric laminate under unidirectional tension. Both analytical models for stepped-scarf repair and tapered-scarf repair were built, including the structures without extra plies, with one extra ply and with two extra plies. The algorithms were developed and accuracy degree was defined, to assess the accuracy of numerical calculation, implementing a user-friendly software program for the design and analysis of composite scarf repair under tensile load. By running the software, the shear stress/strain distribution in the adhesive layer can be presented, the failure level of repair patch and the base laminate can be evaluated and the ultimate failure load and failure modes can be predicted. T300/CYCOM-970 was used as adherent while METLBOND 1515-4M was used as adhesive. A series of corresponding experiments were conducted for validation. The results calculated by this software show a good agreement with experiment outcomes that the relative errors for stepped-scarf repair are less than 5.7% and the relative errors for tapered-scarf repair are less than 14.0%. This software provides an efficient and accurate preliminary design and analysis tool for the scarf repair of composite fabric laminates.
2017, 34(7): 1462-1468.
doi: 10.13801/j.cnki.fhclxb.20170121.001
Abstract:
The composite wind turbine blade was simplified to a symmetric un-uniform laminate beam for researching its bend-twist coupling effect. The influence of coupling area on bend-twist coupling effect was studied by experiment and numerical analysis method. The ply layouts and manufacturing method of symmetric un-uniform laminated plate beams were presented. The bend-twist coupling test of symmetric un-uniform laminated plate beams was designed, in which the principle and measuring method of the experiment were given. The deflection and twist angle of un-uniform symmetric laminated plate beams were tested in the experiment. The finite element models were established based on ANSYS software and their deformations were got under the concentrated force. Comparing the numerical results with the experimental results, it shows that coupling area has an important influence to deformational behavior of symmetric un-uniform laminated plate beams and coupling in central region can obtain remarkable bend-twist coupling effect.
The composite wind turbine blade was simplified to a symmetric un-uniform laminate beam for researching its bend-twist coupling effect. The influence of coupling area on bend-twist coupling effect was studied by experiment and numerical analysis method. The ply layouts and manufacturing method of symmetric un-uniform laminated plate beams were presented. The bend-twist coupling test of symmetric un-uniform laminated plate beams was designed, in which the principle and measuring method of the experiment were given. The deflection and twist angle of un-uniform symmetric laminated plate beams were tested in the experiment. The finite element models were established based on ANSYS software and their deformations were got under the concentrated force. Comparing the numerical results with the experimental results, it shows that coupling area has an important influence to deformational behavior of symmetric un-uniform laminated plate beams and coupling in central region can obtain remarkable bend-twist coupling effect.
2017, 34(7): 1469-1477.
doi: 10.13801/j.cnki.fhclxb.20161012.001
Abstract:
In order to study the buckling behavior and failure model of composite cylindrical shell with aspect ratio greater than 1 subject to axial compression, the axial compression tests for two unidirectional fiber composite cylindrical shells and three composite cylindrical shells wrapped hoop fiber were conducted, respectively. The failure model, load-displacement relationship and load-strain relationship were documented during the loading process. Then, the failure mechanisms of two unidirectional fiber composite cylindrical shells were numerical analyzed and the axial compression behaviors of those two shells were comparative analyzed. The results show that there are two failure models for unidirectional fiber composite cylindrical shell under axial compression: the longitudinal splitting of cylindrical shell followed by the buckling of each plates, or the buckling of the cylindrical shell followed by the longitudinal splitting; the outer hoop fibers can improve the behavior of cylindrical shells under axial compression, and the buckling process has certain stages showing that ductile characteristics and stable carrying capacity and failure modes.
In order to study the buckling behavior and failure model of composite cylindrical shell with aspect ratio greater than 1 subject to axial compression, the axial compression tests for two unidirectional fiber composite cylindrical shells and three composite cylindrical shells wrapped hoop fiber were conducted, respectively. The failure model, load-displacement relationship and load-strain relationship were documented during the loading process. Then, the failure mechanisms of two unidirectional fiber composite cylindrical shells were numerical analyzed and the axial compression behaviors of those two shells were comparative analyzed. The results show that there are two failure models for unidirectional fiber composite cylindrical shell under axial compression: the longitudinal splitting of cylindrical shell followed by the buckling of each plates, or the buckling of the cylindrical shell followed by the longitudinal splitting; the outer hoop fibers can improve the behavior of cylindrical shells under axial compression, and the buckling process has certain stages showing that ductile characteristics and stable carrying capacity and failure modes.
2017, 34(7): 1478-1488.
doi: 10.13801/j.cnki.fhclxb.20161028.001
Abstract:
A finite element method for the modal damping analysis of composite structures by using a general purpose finite element software was proposed. The method was based on an extended elastic-viscoelastic correspondence principle, which accounted the frequency dependence of viscoelastic complex stiffness matrices. The implementation of the proposed model was described as a UMAT subroutine for ABAQUS/Standard. Subsequently, the analyses of modal damping and frequency response for laminated composites were implemented by using the complex eigenvalue method. As compared with existing approaches, the computed results from this model are more close to the test data. Thus the proposed numerical method is quite efficient and accurate, and capable of providing an effective way to determine the modal damping of anisotropic materials by using ABAQUS code.
A finite element method for the modal damping analysis of composite structures by using a general purpose finite element software was proposed. The method was based on an extended elastic-viscoelastic correspondence principle, which accounted the frequency dependence of viscoelastic complex stiffness matrices. The implementation of the proposed model was described as a UMAT subroutine for ABAQUS/Standard. Subsequently, the analyses of modal damping and frequency response for laminated composites were implemented by using the complex eigenvalue method. As compared with existing approaches, the computed results from this model are more close to the test data. Thus the proposed numerical method is quite efficient and accurate, and capable of providing an effective way to determine the modal damping of anisotropic materials by using ABAQUS code.
2017, 34(7): 1489-1495.
doi: 10.13801/j.cnki.fhclxb.20161018.003
Abstract:
Taking time-temperature dependent properties of composites into consideration, storage modulus segments of cured 5228A resin was obtained within a certain experimental window by dynamic mechanical analysis (DMA) under different temperatures. Master curve was constructed by closed form shifting (CFS), which corresponding shift factors resulted from. Constant strain rate (CSR) compression master curves were established based on accelerated testing methodology (ATM), studying quasi-isotropic open-hole CCF300/5228A laminates of two kinds of layup. By means of macro photography and C-scan, the damage processes and failure modes were investigated under different temperatures. The results show that dynamic mechanical properties of resin decrease with the increasing time even though with temperature range below the glass transition temperature; strength of thicker-ply laminates is more sensitive to time and temperature changes, while thinner-ply ones possess better damage tolerance property; the dominant factor of final failure tends to be micro-bulking of fiber instead of delamination as temperature rises and loading rate decreases.
Taking time-temperature dependent properties of composites into consideration, storage modulus segments of cured 5228A resin was obtained within a certain experimental window by dynamic mechanical analysis (DMA) under different temperatures. Master curve was constructed by closed form shifting (CFS), which corresponding shift factors resulted from. Constant strain rate (CSR) compression master curves were established based on accelerated testing methodology (ATM), studying quasi-isotropic open-hole CCF300/5228A laminates of two kinds of layup. By means of macro photography and C-scan, the damage processes and failure modes were investigated under different temperatures. The results show that dynamic mechanical properties of resin decrease with the increasing time even though with temperature range below the glass transition temperature; strength of thicker-ply laminates is more sensitive to time and temperature changes, while thinner-ply ones possess better damage tolerance property; the dominant factor of final failure tends to be micro-bulking of fiber instead of delamination as temperature rises and loading rate decreases.
2017, 34(7): 1496-1504.
doi: 10.13801/j.cnki.fhclxb.20161024.003
Abstract:
Through the tensile tests, the tensile properties of fiber reinforced polymer (FRP) sheet exposed to severe environment were studied. Test parameters included the category and working way of severe environment, the type and layer of FRP sheet. The experimental results show that the tensile stress-strain curves of carbon fiber reinforced polymer (CFRP) sheet and glass fiber reinforced polymer (GFRP) sheet are approximately straight line at ambient temperature and after the action of freeze-thaw cycles and dry-wet cycles, the tensile strength and elongation of CFRP sheet and GFRP sheet at ambient temperature are almost not affected by the number of sheet. The effect of freeze-thaw cycles on GFRP sheet is larger than that on CFRP sheet; the tensile strength of CFRP sheet and GFRP sheet after 75 cycles of freeze-thaw is 0.978 and 0.898 times as much as 0 cycle of freeze-thaw respectively, and with the increasing number of cycles, the tensile strengths of CFRP sheet and GFRP sheet are gradually decreased; wet and dry cycles have no obvious effect on GFRP sheet. Based on the analysis of test results in the literatures and this paper, the calculation method of tensile strength of FRP sheet exposed to severe environment has been presented.
Through the tensile tests, the tensile properties of fiber reinforced polymer (FRP) sheet exposed to severe environment were studied. Test parameters included the category and working way of severe environment, the type and layer of FRP sheet. The experimental results show that the tensile stress-strain curves of carbon fiber reinforced polymer (CFRP) sheet and glass fiber reinforced polymer (GFRP) sheet are approximately straight line at ambient temperature and after the action of freeze-thaw cycles and dry-wet cycles, the tensile strength and elongation of CFRP sheet and GFRP sheet at ambient temperature are almost not affected by the number of sheet. The effect of freeze-thaw cycles on GFRP sheet is larger than that on CFRP sheet; the tensile strength of CFRP sheet and GFRP sheet after 75 cycles of freeze-thaw is 0.978 and 0.898 times as much as 0 cycle of freeze-thaw respectively, and with the increasing number of cycles, the tensile strengths of CFRP sheet and GFRP sheet are gradually decreased; wet and dry cycles have no obvious effect on GFRP sheet. Based on the analysis of test results in the literatures and this paper, the calculation method of tensile strength of FRP sheet exposed to severe environment has been presented.
2017, 34(7): 1505-1510.
doi: 10.13801/j.cnki.fhclxb.20161024.004
Abstract:
The micro-Raman spectroscopy was used to investigate the micromechanics of the ultrahigh molecular weight polyethylene (UHMWPE) bridging fiber crossing crack. The crack-arrest of the bridging fiber and the stress distribution of the interface between the bridging fibers and epoxy were mainly discussed by the micro-tension test coupled with Raman scanning. The crack propagation speed and the stress distribution of the specimens in different positions were also analyzed, and the shear-lag model was proposed to fit the stress distribution of bridging fibers at different tensile. The results show that bridging fibers, by dispersing partial external stress, can effectively withstand the propagation of crack. When the tensile strain is lower than the maximum strain of the UHMWPE fiber, the maximum stress on the bridging fibers existing at the crack center position, is less than 2 GPa, but the stress in the matrix is up to 12 GPa, which indicate the stress transfer value of fiber/matrix interface is less than 100%. The stress transfer model of UHMWPE bridging fibers is proposed to be parabola shaped, and the stress distribution of UHMWPE fiber exists in three zones, namely the bonded zone, the debonded zone and the bridging zone.
The micro-Raman spectroscopy was used to investigate the micromechanics of the ultrahigh molecular weight polyethylene (UHMWPE) bridging fiber crossing crack. The crack-arrest of the bridging fiber and the stress distribution of the interface between the bridging fibers and epoxy were mainly discussed by the micro-tension test coupled with Raman scanning. The crack propagation speed and the stress distribution of the specimens in different positions were also analyzed, and the shear-lag model was proposed to fit the stress distribution of bridging fibers at different tensile. The results show that bridging fibers, by dispersing partial external stress, can effectively withstand the propagation of crack. When the tensile strain is lower than the maximum strain of the UHMWPE fiber, the maximum stress on the bridging fibers existing at the crack center position, is less than 2 GPa, but the stress in the matrix is up to 12 GPa, which indicate the stress transfer value of fiber/matrix interface is less than 100%. The stress transfer model of UHMWPE bridging fibers is proposed to be parabola shaped, and the stress distribution of UHMWPE fiber exists in three zones, namely the bonded zone, the debonded zone and the bridging zone.
2017, 34(7): 1511-1516.
doi: 10.13801/j.cnki.fhclxb.20161020.002
Abstract:
For environmental protection and sustainable development, the recycling and reusing of wasted non-woven fabrics has become a hot research topic in the field of materials. In this thesis, the recycled polyethylene terephthalate (PET) fiber was made from wasted non-woven fabrics, which was used to prepare PET/polypropylene (PP) composites with different fiber content by a hot pressing molding technique. A combination of SEM, DSC, XRD and tensile test was performed to provide a more comprehensive analysis of the structure and mechanical property of the PET/PP composites. The main results are as follows: the recycled PET fiber can be well dispersed in PP matrix at low content, and the interfacial adhesion between them is strong. Crystallinzation of PP molecular chain can be promoted with the addition of PET fiber owing to heterogeneous nucleation effect. Moreover, PET fiber is of advantage to increase the degree of crystallinity and grain refinement of PP, which can improve the mechanical property of the PET/PP composites. When the PET fiber content is only 0.1%, the tensile strength of the PET/PP composites is increased by 25.99% and the toughness thereof increased by 61.96%.
For environmental protection and sustainable development, the recycling and reusing of wasted non-woven fabrics has become a hot research topic in the field of materials. In this thesis, the recycled polyethylene terephthalate (PET) fiber was made from wasted non-woven fabrics, which was used to prepare PET/polypropylene (PP) composites with different fiber content by a hot pressing molding technique. A combination of SEM, DSC, XRD and tensile test was performed to provide a more comprehensive analysis of the structure and mechanical property of the PET/PP composites. The main results are as follows: the recycled PET fiber can be well dispersed in PP matrix at low content, and the interfacial adhesion between them is strong. Crystallinzation of PP molecular chain can be promoted with the addition of PET fiber owing to heterogeneous nucleation effect. Moreover, PET fiber is of advantage to increase the degree of crystallinity and grain refinement of PP, which can improve the mechanical property of the PET/PP composites. When the PET fiber content is only 0.1%, the tensile strength of the PET/PP composites is increased by 25.99% and the toughness thereof increased by 61.96%.
2017, 34(7): 1517-1525.
doi: 10.13801/j.cnki.fhclxb.20161115.009
Abstract:
Series of magnesium oxysulfate/polypropylene (MOS/PP) composites magnesium oxysulfate particle (MOSP), magnesium oxysulfate whisker (MOSW), and magnesium oxysulfate sector (MOSS) were prepared via melt blending method using magnesium oxysulfate (magnesium oxysulfate particle (MOSP), magnesium oxysulfate whisker (MOSW), and magnesium oxysulfate sector (MOSS)) as fillers, lauric acid (LA) as modifier and PP resin as the matrix. SEM results indicate that both modified MOSP and MOSW are fine dispersed in the PP matrix, whereas the incompatibility issue still exist. For MOSS/PP composites, MOSS with huge size and complicated morphology and partial dispersed MOSW are coexisted, with more interface defects observed. Wide angle X-ray diffraction (WXRD) results suggest that addition of MOS can induce the formation of β-crystal PP which is irrelevant to LA, especially for the MOSP/PP sample. The incorporation of three kinds of MOS slightly decreases yield strength of the PP matrix. One reason is the incompatibility between MOS and the PP matrix, and the formation of β-crystal is another important reason. In contrast, introducing MOSW can maintain the yield strength and tension fracture toughness and reinforce the modulus of PP matrix obviously, which is mainly due to the high aspect ratios of whisker morphology. In addition, the most obviously toughening effect happens on the MOSP/PP composites for two reasons. On the one hand, MOSP is more efficient for inducing β-crystal PP as compared with MOSW and MOSS. On the other hand, the more fatty acid salt attached to the surface of MOSP results in the stronger plastification effect to the PP matrix.
Series of magnesium oxysulfate/polypropylene (MOS/PP) composites magnesium oxysulfate particle (MOSP), magnesium oxysulfate whisker (MOSW), and magnesium oxysulfate sector (MOSS) were prepared via melt blending method using magnesium oxysulfate (magnesium oxysulfate particle (MOSP), magnesium oxysulfate whisker (MOSW), and magnesium oxysulfate sector (MOSS)) as fillers, lauric acid (LA) as modifier and PP resin as the matrix. SEM results indicate that both modified MOSP and MOSW are fine dispersed in the PP matrix, whereas the incompatibility issue still exist. For MOSS/PP composites, MOSS with huge size and complicated morphology and partial dispersed MOSW are coexisted, with more interface defects observed. Wide angle X-ray diffraction (WXRD) results suggest that addition of MOS can induce the formation of β-crystal PP which is irrelevant to LA, especially for the MOSP/PP sample. The incorporation of three kinds of MOS slightly decreases yield strength of the PP matrix. One reason is the incompatibility between MOS and the PP matrix, and the formation of β-crystal is another important reason. In contrast, introducing MOSW can maintain the yield strength and tension fracture toughness and reinforce the modulus of PP matrix obviously, which is mainly due to the high aspect ratios of whisker morphology. In addition, the most obviously toughening effect happens on the MOSP/PP composites for two reasons. On the one hand, MOSP is more efficient for inducing β-crystal PP as compared with MOSW and MOSS. On the other hand, the more fatty acid salt attached to the surface of MOSP results in the stronger plastification effect to the PP matrix.
2017, 34(7): 1526-1532.
doi: 10.13801/j.cnki.fhclxb.20161115.005
Abstract:
A series of nano-ZnO/polypropylene (PP) composites were prepared via melt blending. The effect of compatibilizer maleic anhydride grafted polypropylene (PP-g-MAH) on nucleation and crystallization behavior, crystal structure, morphology and mechanical properties of nano-ZnO/PP composites was investigated. The results show that nano-ZnO has good effect on the β-crystal nucleation of PP when nano-ZnO is added in low level (mass fraction less than 5%). When the mass fraction of nano-ZnO is more than 5%, nano-ZnO has obvious heterogeneous nucleation effect on PP matrix, with the cryatallization peak temperature of PP shifted to higher temperature significantly, and PP presents preferential growth in (040) crystal face. PP-g-MAH enhances the interfacial interaction between nano-ZnO particles and PP matrix, which improves the dispersion of nanoparticles, and promotes the heterogeneous nucleation of PP matrix. Consequently, the tensile strength and impact strength of nano-ZnO/PP composites are improved obviously. However, the ability of β-crystal induced by nano-ZnO is inhibited. The toughness of nano-ZnO/PP nanocomposites improved due to better interaction interface is significantly stronger than the β-crystal toughening effect induced by nano-ZnO.
A series of nano-ZnO/polypropylene (PP) composites were prepared via melt blending. The effect of compatibilizer maleic anhydride grafted polypropylene (PP-g-MAH) on nucleation and crystallization behavior, crystal structure, morphology and mechanical properties of nano-ZnO/PP composites was investigated. The results show that nano-ZnO has good effect on the β-crystal nucleation of PP when nano-ZnO is added in low level (mass fraction less than 5%). When the mass fraction of nano-ZnO is more than 5%, nano-ZnO has obvious heterogeneous nucleation effect on PP matrix, with the cryatallization peak temperature of PP shifted to higher temperature significantly, and PP presents preferential growth in (040) crystal face. PP-g-MAH enhances the interfacial interaction between nano-ZnO particles and PP matrix, which improves the dispersion of nanoparticles, and promotes the heterogeneous nucleation of PP matrix. Consequently, the tensile strength and impact strength of nano-ZnO/PP composites are improved obviously. However, the ability of β-crystal induced by nano-ZnO is inhibited. The toughness of nano-ZnO/PP nanocomposites improved due to better interaction interface is significantly stronger than the β-crystal toughening effect induced by nano-ZnO.
2017, 34(7): 1533-1539.
doi: 10.13801/j.cnki.fhclxb.20161018.002
Abstract:
The superaligned carbon nanotube (SACNT) film/silicone composites with different carbon nanotube layers were made by the method of direct infiltration. Thorough this method, the carbon nanotube can be homogenously embedded in the surface of silicone matrix. The electrical and mechanical properties of the SACNT film/silicone composites along different directions were tested, and the factors that affect the electrical conductivity and mechanical properties were investigated. The SACNT film/silicone composites show an inspiring anisotropic electrical and mechanical properties, and the properties increase along with the increasing layer number of the SACNT film. The resistivity of the composite along the CNT aligned direction is about one order of magnitude larger than that along the perpendicular direction. For the composite with 240 CNT film layers, the Young's modulus along the CNT aligned direction is 116.9 MPa (142 times larger than the pure silicone matrix) while only 1.23 MPa (50.0% improvement) is got along perpendicular direction, and the difference between them is about 100 times. SACNT film/silicone composites with different parameters can be chosen to meet the proper conductivity and the Young's modulus for the practical applications.
The superaligned carbon nanotube (SACNT) film/silicone composites with different carbon nanotube layers were made by the method of direct infiltration. Thorough this method, the carbon nanotube can be homogenously embedded in the surface of silicone matrix. The electrical and mechanical properties of the SACNT film/silicone composites along different directions were tested, and the factors that affect the electrical conductivity and mechanical properties were investigated. The SACNT film/silicone composites show an inspiring anisotropic electrical and mechanical properties, and the properties increase along with the increasing layer number of the SACNT film. The resistivity of the composite along the CNT aligned direction is about one order of magnitude larger than that along the perpendicular direction. For the composite with 240 CNT film layers, the Young's modulus along the CNT aligned direction is 116.9 MPa (142 times larger than the pure silicone matrix) while only 1.23 MPa (50.0% improvement) is got along perpendicular direction, and the difference between them is about 100 times. SACNT film/silicone composites with different parameters can be chosen to meet the proper conductivity and the Young's modulus for the practical applications.
2017, 34(7): 1540-1546.
doi: 10.13801/j.cnki.fhclxb.20161014.001
Abstract:
Surface porous NiTi-Hydroxyapatite(HA)/NiTi biocomposites were prepared by spark plasma sintering (SPS) technology. The effects of different sintering temperatures on the macroscopic morphology, microstructure, surface pore characteristics, mechanical properties and in vitro biological activity of the composites were investigated. The results show that the NiTi-HA/NiTi biocomposites are consisted of complex Ti, Ni, Ti2Ni, Ni3Ti, HA mixed phase and gradually transformed into a single NiTi+HA phase with increasing of sintering temperatures form 800℃ to 950℃. Furthermore, a stable metallurgical bonding on the internal and external interface of the composites can be observed. Meanwhile, the porosity and average pore size of surface layer are in a slowly decreasing trend. As a result, compressive strength of the composites is significantly increased, but compressive elastic modulus of the composites is changed not obvious. Compared with NiTi, porous NiTi and porous NiTi-HA, NiTi-HA/NiTi biocomposites sintered at 950℃ not only exhibits a best match with better interface bonding, good surface pore characteristics (45.6% porosity as well as 393 μm average pore size), higher compressive strength (1 301 MPa), lower the compressive elastic modulus (10.2 GPa) and excellent superelastic recovery strain (>4%), but also showes a good in vitro biological activity.
Surface porous NiTi-Hydroxyapatite(HA)/NiTi biocomposites were prepared by spark plasma sintering (SPS) technology. The effects of different sintering temperatures on the macroscopic morphology, microstructure, surface pore characteristics, mechanical properties and in vitro biological activity of the composites were investigated. The results show that the NiTi-HA/NiTi biocomposites are consisted of complex Ti, Ni, Ti2Ni, Ni3Ti, HA mixed phase and gradually transformed into a single NiTi+HA phase with increasing of sintering temperatures form 800℃ to 950℃. Furthermore, a stable metallurgical bonding on the internal and external interface of the composites can be observed. Meanwhile, the porosity and average pore size of surface layer are in a slowly decreasing trend. As a result, compressive strength of the composites is significantly increased, but compressive elastic modulus of the composites is changed not obvious. Compared with NiTi, porous NiTi and porous NiTi-HA, NiTi-HA/NiTi biocomposites sintered at 950℃ not only exhibits a best match with better interface bonding, good surface pore characteristics (45.6% porosity as well as 393 μm average pore size), higher compressive strength (1 301 MPa), lower the compressive elastic modulus (10.2 GPa) and excellent superelastic recovery strain (>4%), but also showes a good in vitro biological activity.
2017, 34(7): 1547-1551.
doi: 10.13801/j.cnki.fhclxb.20160914.001
Abstract:
By analyzing the reaction between matrix (Al) and inclusions (SiC) in SiC particle reinforced aluminum alloy composite under uniaxial loading, a two phase model for accumulation of diffraction elastic constants of SiC particle reinforced aluminum alloy composite was built through using self-consistent model and inclusion model. Several diffraction elastic constants of Al phase and SiC phase were figured out by the two phase model. The results calculated by the two phase model of {101} and {116} of SiC and {222} of Al are all highly coincided with test results, which give only a difference of less than 6%. And the others show difference of less than 15%. All results show the theoretical model is reliable and can predict accurately. This kind of predict model can not only avoid the tedious experiment and save the money, but also can make accurate predictions of some materials difficult to test.
By analyzing the reaction between matrix (Al) and inclusions (SiC) in SiC particle reinforced aluminum alloy composite under uniaxial loading, a two phase model for accumulation of diffraction elastic constants of SiC particle reinforced aluminum alloy composite was built through using self-consistent model and inclusion model. Several diffraction elastic constants of Al phase and SiC phase were figured out by the two phase model. The results calculated by the two phase model of {101} and {116} of SiC and {222} of Al are all highly coincided with test results, which give only a difference of less than 6%. And the others show difference of less than 15%. All results show the theoretical model is reliable and can predict accurately. This kind of predict model can not only avoid the tedious experiment and save the money, but also can make accurate predictions of some materials difficult to test.
2017, 34(7): 1552-1560.
doi: 10.13801/j.cnki.fhclxb.20161114.001
Abstract:
The Ni-Co/WC-Graphite composite coating was fabricated by vacuum cladding. The microstructure and composition of the composite coating were characterized and analyzed by SEM and XRD. The bending behavior was studied through three point bending test, and the fracture characteristics, elements analysis and fracture mechanism were discussed. The results show that the whole composite coating consists of composite area, transition area, diffusion-fusion strip and heat-affected area. The WC particles well-distribute among the composite coating and form a 3D reticular microstructure characteristic. The main phases are Cr7C3, Cr23C6, Ni3Si, CrB, WC, C and γ-Ni-Co solid solution in the composite coating. The pearlite is the main phase at heat-affected area. There are γ-Ni-Co solid solution and intermetallics in fusion area and transition area. Three point bending test show that the load-distance curve presents linear change at the initial state, and then the slope of curve decreased. The composite coating debacle happens as the load reaches a maximum when the composite coating bears compress stress, and fracture happens as the load reaches a maximum when the composite coating bears tensile stress. The load increases slowly after the composite coating failure because of the forming of the transition area, diffusion-fusion strip and heat-affected area. The fracture characteristics present intergranular or transgranular at composite coating area. The fracture presents fan cleavage characteristics at the heat-affected area, and there are many dimples at substrate area.
The Ni-Co/WC-Graphite composite coating was fabricated by vacuum cladding. The microstructure and composition of the composite coating were characterized and analyzed by SEM and XRD. The bending behavior was studied through three point bending test, and the fracture characteristics, elements analysis and fracture mechanism were discussed. The results show that the whole composite coating consists of composite area, transition area, diffusion-fusion strip and heat-affected area. The WC particles well-distribute among the composite coating and form a 3D reticular microstructure characteristic. The main phases are Cr7C3, Cr23C6, Ni3Si, CrB, WC, C and γ-Ni-Co solid solution in the composite coating. The pearlite is the main phase at heat-affected area. There are γ-Ni-Co solid solution and intermetallics in fusion area and transition area. Three point bending test show that the load-distance curve presents linear change at the initial state, and then the slope of curve decreased. The composite coating debacle happens as the load reaches a maximum when the composite coating bears compress stress, and fracture happens as the load reaches a maximum when the composite coating bears tensile stress. The load increases slowly after the composite coating failure because of the forming of the transition area, diffusion-fusion strip and heat-affected area. The fracture characteristics present intergranular or transgranular at composite coating area. The fracture presents fan cleavage characteristics at the heat-affected area, and there are many dimples at substrate area.
2017, 34(7): 1561-1568.
doi: 10.13801/j.cnki.fhclxb.20161110.002
Abstract:
2D CF/SiC composites were prepared by liquid silicon infiltration. XRD analysis revealed that SiC only presents as β phase in composites. The mixed solution of K3Fe(CN)6 and KOH in the same mass ratio was used to corrosive the material. SEM images show that coarse and fine two morphological of the grains exist in 2D CF/SiC composites. It's conclude that distinguishing shapes of SiC are produced by two different growth theory: silicon atoms diffuse into carbon through the vacancy mechanism which leads to the appearance of amorphous SiC. As heat-retaining time increasing, amorphous SiC gradually transforms into the crystalline state. After the carbon atoms diffuse through the silicon carbide layer, carbon atoms dissolve in the liquid silicon and exist in the form of C—Si group. Under the influence of temperature gradient and concentration gradient, Si—C group move farther away from the C/SiC interface and begin to nucleate after reach saturation.Coarse silicon carbide crystals are formed by the dissolution-precipitation mechanism, which accompany the emergence of stacking fault.
2D CF/SiC composites were prepared by liquid silicon infiltration. XRD analysis revealed that SiC only presents as β phase in composites. The mixed solution of K3Fe(CN)6 and KOH in the same mass ratio was used to corrosive the material. SEM images show that coarse and fine two morphological of the grains exist in 2D CF/SiC composites. It's conclude that distinguishing shapes of SiC are produced by two different growth theory: silicon atoms diffuse into carbon through the vacancy mechanism which leads to the appearance of amorphous SiC. As heat-retaining time increasing, amorphous SiC gradually transforms into the crystalline state. After the carbon atoms diffuse through the silicon carbide layer, carbon atoms dissolve in the liquid silicon and exist in the form of C—Si group. Under the influence of temperature gradient and concentration gradient, Si—C group move farther away from the C/SiC interface and begin to nucleate after reach saturation.Coarse silicon carbide crystals are formed by the dissolution-precipitation mechanism, which accompany the emergence of stacking fault.
2017, 34(7): 1569-1574.
doi: 10.13801/j.cnki.fhclxb.20161018.004
Abstract:
In order to explore the ablation behavior and repetitive-use feasibility of the C/C-SiC nozzle in the solid propellant ramjet, the C/C-SiC composite nozzle was experimentally investigated. The results show that the C/C-SiC composite nozzle can work safely under the oxygen-rich combustion environment of the ramjet for long test duration. The thickness of convergent section of the nozzle reduces and the ablation mechanism are suggested as the thermochemical ablation and thermal-mechanical erosion. Thermochemical ablation is the dominated ablation mechanism for the nozzle throat with the thickness not reduced appreciably. No obvious oxidation and thickness reduction are observed in the divergent section of the nozzle. The circumferential and axial flexural strength of the convergent section descend obviously while the divergent section descend insignificantly after test, which can also satisfy for repetitive-use of the nozzle. Hence for the safety and reliability of the repetitive-use nozzle, chemical vapor deposition SiC coating in different positions of the after-test nozzle should be optimally designed for improving the anti-oxidation performance of the throat upstream.
In order to explore the ablation behavior and repetitive-use feasibility of the C/C-SiC nozzle in the solid propellant ramjet, the C/C-SiC composite nozzle was experimentally investigated. The results show that the C/C-SiC composite nozzle can work safely under the oxygen-rich combustion environment of the ramjet for long test duration. The thickness of convergent section of the nozzle reduces and the ablation mechanism are suggested as the thermochemical ablation and thermal-mechanical erosion. Thermochemical ablation is the dominated ablation mechanism for the nozzle throat with the thickness not reduced appreciably. No obvious oxidation and thickness reduction are observed in the divergent section of the nozzle. The circumferential and axial flexural strength of the convergent section descend obviously while the divergent section descend insignificantly after test, which can also satisfy for repetitive-use of the nozzle. Hence for the safety and reliability of the repetitive-use nozzle, chemical vapor deposition SiC coating in different positions of the after-test nozzle should be optimally designed for improving the anti-oxidation performance of the throat upstream.
2017, 34(7): 1575-1581.
doi: 10.13801/j.cnki.fhclxb.20161019.001
Abstract:
The first heat shock factor model of BNNTs reinforced ceramic composites was constructed based on Kingery thermal shock theory. The BNNTs/Si3N4 composites with mass fractions of 0.5wt%, 1.0wt%, 1.5wt% and 2.0wt% were prepared by hot pressed sintering process. The thermal shock resistance of the BNNTs/Si3N4 composites, including bending strength after thermal shock and critical fracture temperature difference, was tested by water bath quenching and three point bending method. The first heat shock factor model is verified by the thermal shock resistance test, which indicates that the thermal shock performance of BNNTs/Si3N4 is enhanced by the BNNTs. BNNTs which are distributed on the grain boundary make the crack pinned and deflected, increasing the crack propagation resistance. Moreover, the hole of the nanotube changes the crack propagation path, improving the fracture resistance and thermal shock resistance of the BNNTs/Si3N4 composites.
The first heat shock factor model of BNNTs reinforced ceramic composites was constructed based on Kingery thermal shock theory. The BNNTs/Si3N4 composites with mass fractions of 0.5wt%, 1.0wt%, 1.5wt% and 2.0wt% were prepared by hot pressed sintering process. The thermal shock resistance of the BNNTs/Si3N4 composites, including bending strength after thermal shock and critical fracture temperature difference, was tested by water bath quenching and three point bending method. The first heat shock factor model is verified by the thermal shock resistance test, which indicates that the thermal shock performance of BNNTs/Si3N4 is enhanced by the BNNTs. BNNTs which are distributed on the grain boundary make the crack pinned and deflected, increasing the crack propagation resistance. Moreover, the hole of the nanotube changes the crack propagation path, improving the fracture resistance and thermal shock resistance of the BNNTs/Si3N4 composites.
2017, 34(7): 1582-1588.
doi: 10.13801/j.cnki.fhclxb.20161110.003
Abstract:
Amorphous SiO2 coating was prepared on the surface of carbon/carbon composites by low pressure chemical vapor deposition (LPCVD) with TEOS as precursor and N2 as carrier gas. The effects of deposition temperature on the component, morphology and deposition rate of the coating were studied. The components and morphologies of the coatings were analyzed by XRD, XPS, FTIR, SEM and EDS, and the bioactivity of film was detected by the in vitro simulated body fluid (SBF) soaking. The results show that the main phase of the coating is amorphous SiO2, and a thin layer of bone-like hydroxyapatite is deposited on the surface of the SiO2 coating after soaking at 35 days which proves the coating has better bioactivity than that of the bare substrate. The deposition rate is increased with the development of temperature, and at the same time, the morphology of SiO2 particles change from irregular to spherical and polygon shape finally.
Amorphous SiO2 coating was prepared on the surface of carbon/carbon composites by low pressure chemical vapor deposition (LPCVD) with TEOS as precursor and N2 as carrier gas. The effects of deposition temperature on the component, morphology and deposition rate of the coating were studied. The components and morphologies of the coatings were analyzed by XRD, XPS, FTIR, SEM and EDS, and the bioactivity of film was detected by the in vitro simulated body fluid (SBF) soaking. The results show that the main phase of the coating is amorphous SiO2, and a thin layer of bone-like hydroxyapatite is deposited on the surface of the SiO2 coating after soaking at 35 days which proves the coating has better bioactivity than that of the bare substrate. The deposition rate is increased with the development of temperature, and at the same time, the morphology of SiO2 particles change from irregular to spherical and polygon shape finally.
2017, 34(7): 1589-1595.
doi: 10.13801/j.cnki.fhclxb.20161013.002
Abstract:
Nickel hydroxide/reduced graphene oxide (Ni(OH)2/RGO) composites were synthesized by simple and practicable chemical precipitation-reflux method. The influence of different ammonia-alkali mixed precipitant on electrochemical performance of composite materials was researched. The microstructure and morphology of the Ni(OH)2/RGO composites were characterized by XRD, Raman spectra and SEM. The synthesized Ni(OH)2/RGO composite shows that β-Ni(OH)2 nano sheets are homogeneously dispersed and inserted into RGO sheets, thus mutually inserted structure is formed using ammonium hydroxide-sodium hydroxide as precipitant. The electrochemical characteristics of composite electrode materials were tested by cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) and electrochemical impedance spectroscopy (EIS). The results show that the prepared Ni(OH)2/RGO composite exhibits a high discharge specific capacity of 344.8 mAh/g at 0.2 C rate, and is 29% higher than the specific capacity of β-Ni(OH)2. The discharge specific capacity of the β-Ni(OH)2/RGO composite is 274.5 mAh/g at 5 C rate. Moreover, 98.8% of the initial specific capacity of the composite is maintained after 50 cycle test. Ni(OH)2/RGO composite displays a better rate capability and cycle performance as electrode material.
Nickel hydroxide/reduced graphene oxide (Ni(OH)2/RGO) composites were synthesized by simple and practicable chemical precipitation-reflux method. The influence of different ammonia-alkali mixed precipitant on electrochemical performance of composite materials was researched. The microstructure and morphology of the Ni(OH)2/RGO composites were characterized by XRD, Raman spectra and SEM. The synthesized Ni(OH)2/RGO composite shows that β-Ni(OH)2 nano sheets are homogeneously dispersed and inserted into RGO sheets, thus mutually inserted structure is formed using ammonium hydroxide-sodium hydroxide as precipitant. The electrochemical characteristics of composite electrode materials were tested by cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) and electrochemical impedance spectroscopy (EIS). The results show that the prepared Ni(OH)2/RGO composite exhibits a high discharge specific capacity of 344.8 mAh/g at 0.2 C rate, and is 29% higher than the specific capacity of β-Ni(OH)2. The discharge specific capacity of the β-Ni(OH)2/RGO composite is 274.5 mAh/g at 5 C rate. Moreover, 98.8% of the initial specific capacity of the composite is maintained after 50 cycle test. Ni(OH)2/RGO composite displays a better rate capability and cycle performance as electrode material.
2017, 34(7): 1596-1602.
doi: 10.13801/j.cnki.fhclxb.20161018.007
Abstract:
The magnetic TiO2-Fe3O4/MIL(Material Institute Lavoisier)-101(Cr) composites were synthesized via in situ hydrothermal method. The structure and performance of composites were characterized by XRD, SEM, UV-Vis DRS, BET and superconducting magnet system. The photocatalytic activity of TiO2-Fe3O4/MIL-101(Cr) composites were investigated by photocatalytic degradation of MB solution, and the stability of TiO2-Fe3O4/MIL-101(Cr) composites was also studied. The results show that the thiohydroxy-modified-Fe3O4 and thiohydroxy-modified-TiO2, can be successfully combined with MIL-101(Cr), and a notable absorption extension in the visible-light region can be observed for the TiO2-Fe3O4/MIL-101(Cr) composites. The TiO2-Fe3O4/MIL-101(Cr)(400) composite exhibits the highest photocatalytic activity, while the corresponding photodegradation efficiency for MB is 80% after 120 min irradiation. The TiO2-Fe3O4/MIL-101(Cr) composites also have a good stability and can be easily separated from solution by an external magnet.
The magnetic TiO2-Fe3O4/MIL(Material Institute Lavoisier)-101(Cr) composites were synthesized via in situ hydrothermal method. The structure and performance of composites were characterized by XRD, SEM, UV-Vis DRS, BET and superconducting magnet system. The photocatalytic activity of TiO2-Fe3O4/MIL-101(Cr) composites were investigated by photocatalytic degradation of MB solution, and the stability of TiO2-Fe3O4/MIL-101(Cr) composites was also studied. The results show that the thiohydroxy-modified-Fe3O4 and thiohydroxy-modified-TiO2, can be successfully combined with MIL-101(Cr), and a notable absorption extension in the visible-light region can be observed for the TiO2-Fe3O4/MIL-101(Cr) composites. The TiO2-Fe3O4/MIL-101(Cr)(400) composite exhibits the highest photocatalytic activity, while the corresponding photodegradation efficiency for MB is 80% after 120 min irradiation. The TiO2-Fe3O4/MIL-101(Cr) composites also have a good stability and can be easily separated from solution by an external magnet.
2017, 34(7): 1603-1609.
doi: 10.13801/j.cnki.fhclxb.20160920.003
Abstract:
An amino-functionalized nano-Fe3O4 magnetic composite material (NH2-nFe3O4) was synthesized by one-pot solvothermal method. The NH2-nFe3O4 was characterized by EA, XRD, FTIR, TEM and VSM. Its application for adsorption and degradation of pentachlorophenol (PCP) was investigated. The results show that the NH2-nFe3O4 has an average size of about 20 nm, with the saturation magnetization intensity of 56.8 emu/g. The adsorption capacities were investigated by adsorbing the PCP from aqueous solutions. Thermodynamic studies suggest that the adsorption processes fit the Freundlich isotherms well. The adsorption capacity of NH2-nFe3O4 is found to be 899.2 mg/g when the initial concentration of PCP at 1000 mg/L. The adsorption kinetic studies show that the adsorption processes reach the equilibrium within 5 min and the kinetic data are well fitted to the pseudo-second-order model. The post-adsorbed material was added to Fe3+-H2O2 system. In situ degradation of PCP via Fenton-like reaction under visible light can be realized. The results indicate that at pH 3.0—8.0, the degradation of PCP with loading concentration at 6.25—120.0 mg/g can be reached to almost 100% within 5 min. NH2-nFe3O4 can be reused after regeneration. It is a potential effective and reusable material for adsorption and degradation of PCP.
An amino-functionalized nano-Fe3O4 magnetic composite material (NH2-nFe3O4) was synthesized by one-pot solvothermal method. The NH2-nFe3O4 was characterized by EA, XRD, FTIR, TEM and VSM. Its application for adsorption and degradation of pentachlorophenol (PCP) was investigated. The results show that the NH2-nFe3O4 has an average size of about 20 nm, with the saturation magnetization intensity of 56.8 emu/g. The adsorption capacities were investigated by adsorbing the PCP from aqueous solutions. Thermodynamic studies suggest that the adsorption processes fit the Freundlich isotherms well. The adsorption capacity of NH2-nFe3O4 is found to be 899.2 mg/g when the initial concentration of PCP at 1000 mg/L. The adsorption kinetic studies show that the adsorption processes reach the equilibrium within 5 min and the kinetic data are well fitted to the pseudo-second-order model. The post-adsorbed material was added to Fe3+-H2O2 system. In situ degradation of PCP via Fenton-like reaction under visible light can be realized. The results indicate that at pH 3.0—8.0, the degradation of PCP with loading concentration at 6.25—120.0 mg/g can be reached to almost 100% within 5 min. NH2-nFe3O4 can be reused after regeneration. It is a potential effective and reusable material for adsorption and degradation of PCP.
2017, 34(7): 1610-1616.
doi: 10.13801/j.cnki.fhclxb.20160921.001
Abstract:
Based on the dynamic shear rheological test (DSR), the high temperature performance of three kinds of polymer modified asphalt before and after aging:polyphosphoric acid(PPA)modified asphalt, styrene butadiene styrene block copolymer(SBS)modified asphalt and SBS-PPA modified asphalt were analyzed. Results shows that: Under different temperatures and different aging, compared with SBS modified asphalt, the improvement of rheological properties of asphalt at high temperature was more prominent with PPA modifier, the viscosity of asphalt decreases and the elastic component increases. PPA was added in the SBS modified asphalt can obviously improve the elasticity of modified asphalt and reduce its viscosity. The high temperature performance of SBS-PPA modified asphalt is better than that of SBS modified asphalt. Under the long-term aging, the temperature translation point of PPA and SBS-PPA modified asphalt by the storage modulus G' dominant role into the loss modulus G" dominant role become higher, the temperature translation point:PPA >SBS-PPA >>SBS. For SBS modified asphalt, the effect of temperature and frequency on G* and δ are greater than that of aging, but the PPA and SBS-PPA modified asphalt are greatly influenced by aging. As the aging degree of deepening, can the PPA and SBS-PPA modified asphalt maintain a certain degree of flexible to resist deformation in relatively wide temperature and frequency range. PPA modified asphalt before and after aging under different temperatures and frequency have a higher G*/sinδ, and the G*/sinδ increases most after aging, high temperature anti rutting ability becomes stronger, followed by SBS-PPA modified asphalt.
Based on the dynamic shear rheological test (DSR), the high temperature performance of three kinds of polymer modified asphalt before and after aging:polyphosphoric acid(PPA)modified asphalt, styrene butadiene styrene block copolymer(SBS)modified asphalt and SBS-PPA modified asphalt were analyzed. Results shows that: Under different temperatures and different aging, compared with SBS modified asphalt, the improvement of rheological properties of asphalt at high temperature was more prominent with PPA modifier, the viscosity of asphalt decreases and the elastic component increases. PPA was added in the SBS modified asphalt can obviously improve the elasticity of modified asphalt and reduce its viscosity. The high temperature performance of SBS-PPA modified asphalt is better than that of SBS modified asphalt. Under the long-term aging, the temperature translation point of PPA and SBS-PPA modified asphalt by the storage modulus G' dominant role into the loss modulus G" dominant role become higher, the temperature translation point:PPA >SBS-PPA >>SBS. For SBS modified asphalt, the effect of temperature and frequency on G* and δ are greater than that of aging, but the PPA and SBS-PPA modified asphalt are greatly influenced by aging. As the aging degree of deepening, can the PPA and SBS-PPA modified asphalt maintain a certain degree of flexible to resist deformation in relatively wide temperature and frequency range. PPA modified asphalt before and after aging under different temperatures and frequency have a higher G*/sinδ, and the G*/sinδ increases most after aging, high temperature anti rutting ability becomes stronger, followed by SBS-PPA modified asphalt.
2017, 34(7): 1617-1623.
doi: 10.13801/j.cnki.fhclxb.20160926.001
Abstract:
For the typical concrete beams reinforced with the high performance carbon fiber-glass fiber-Epoxy(CF-GF-EP) sheet, a new three dimensional nonlinear hybrid composite element was studied for the nonlinear performances including stiffness reduction, stress redistribution etc. According to the theory of the solid degradation element, the RC beam was modeled with composite element. Then the contribution matrix of hybrid CF-GF-EP sheet to the new nonlinear hybrid composite element was completed through selective integration technique. The corresponding three-dimensional nonlinear analysis program was developed with the material nonlinearity of the concrete such as Jiang yield criterion, Hinton crushing criterion and Madrid criterion. Compared with the experimental data, the calculated results are in good agreement with the experimental data, which shows the correctness of the nonlinear hybrid composite element and the reliability of the developed program are both testified. The derived hybrid composite element can be accurately used for the whole process of analysis of the beams reinforced with the similar high performance CF-GF-EP sheet. In initial loads, the beams reinforced with the high performance CF-GF-EP sheet have no obvious stiffness reduction and then when the yielding loads and ultimate loads are reached, the stiffness reduction coefficients are about 0.6 and 0.9, respectively. Before cracking loads, the stress of the high performance CF-GF-EP sheet increases slowly and the stress redistribution coefficient of the high performance CF-GF-EP sheet changes little and in the following stage, it increases more rapidly until the structure fails.
For the typical concrete beams reinforced with the high performance carbon fiber-glass fiber-Epoxy(CF-GF-EP) sheet, a new three dimensional nonlinear hybrid composite element was studied for the nonlinear performances including stiffness reduction, stress redistribution etc. According to the theory of the solid degradation element, the RC beam was modeled with composite element. Then the contribution matrix of hybrid CF-GF-EP sheet to the new nonlinear hybrid composite element was completed through selective integration technique. The corresponding three-dimensional nonlinear analysis program was developed with the material nonlinearity of the concrete such as Jiang yield criterion, Hinton crushing criterion and Madrid criterion. Compared with the experimental data, the calculated results are in good agreement with the experimental data, which shows the correctness of the nonlinear hybrid composite element and the reliability of the developed program are both testified. The derived hybrid composite element can be accurately used for the whole process of analysis of the beams reinforced with the similar high performance CF-GF-EP sheet. In initial loads, the beams reinforced with the high performance CF-GF-EP sheet have no obvious stiffness reduction and then when the yielding loads and ultimate loads are reached, the stiffness reduction coefficients are about 0.6 and 0.9, respectively. Before cracking loads, the stress of the high performance CF-GF-EP sheet increases slowly and the stress redistribution coefficient of the high performance CF-GF-EP sheet changes little and in the following stage, it increases more rapidly until the structure fails.
