A combined beam model representing the periodicity of the microstructure and micro deformation of 3D woven composites is developed for predicting mechanical properties. The model considers the effects of off axial ten...A combined beam model representing the periodicity of the microstructure and micro deformation of 3D woven composites is developed for predicting mechanical properties. The model considers the effects of off axial tension/compression and bending/shearing couplings as well as the mutual reactions of fiber yarns. The method determining microstructure by using woven parameters is described for a typical 3D woven composite material. An analytical cell, constructed by a minimum periodic section of yarn and interlayer matrix, is adopted. Micro stresses in the cell under in-plane tensile loading are obtained by using the proposed beam model and macro modulus is then obtained by the averaging method. Material tests and a 2D micro FEM analysis are made to evaluate this model. Analyses reveal that micro stress caused by tensile/bending coupling effect is not negligible in the stress analysis.展开更多
A micromechanical model for elastic behavior analysis of angle-interlock woven ceramic composites is proposed in this paper. This model takes into account the actual fabric structure by considering the fiber undulatio...A micromechanical model for elastic behavior analysis of angle-interlock woven ceramic composites is proposed in this paper. This model takes into account the actual fabric structure by considering the fiber undulation and continuity in space, the cavities between adjacent yarns and the actual cross-section geometry of the yarn. Based on the laminate theory, the elastic properties of 3D angle-interlock woven ceramic composites are predicted. Different numbers of interlaced wefts have almost the same elastic moduli. The thickness of ceramic matrix has little effect on elastic moduli. When the undulation ratio increases longitudinal modulus decreases and the other Young＇s moduli increase. Good agreement between theoretical predictions and experimental results demonstrates the feasibility of the proposed model in analyzing the elastic properties of 3D angle-interlock woven ceramic composites. The results of this paper verify the fact that the method of analyzing polyester matrix composites is suitable for woven ceramic composites.展开更多
The 3D fine-woven punctured C/C-(PyC/SiC/TaC)composites,composed of PyC/SiC/TaC interphases and pyrocarbon (PyC)matrix,were synthesized by isothermal chemical vapor infiltration(ICVI)methods.The alternating layers and...The 3D fine-woven punctured C/C-(PyC/SiC/TaC)composites,composed of PyC/SiC/TaC interphases and pyrocarbon (PyC)matrix,were synthesized by isothermal chemical vapor infiltration(ICVI)methods.The alternating layers and the structure of these composites were examined by polarized light microscopy(PLM),X-ray diffractometry(XRD)and scanning electron microscopy(SEM).It is found that the PyC matrix has rough laminar(RL)structure,the TaC layer has NaCl-type cubic structure,and the SiC layer has few wurtzite type 10H-SiC besidesβ-SiC structure.The effects of fiber coating and the bulk density on the tensile and flexural properties of composites along X or Y and Z direction were investigated.It is shown that fiber coated 3D woven punctured C/C composites have good tensile and flexural strength,and the maximum of flexural strength is 375 MPa in X or Y direction at density of 1.89 g/cm 3 ,which is about three times higher than that of samples without TaC/SiC fiber coating.The flexural strength and bending strength increase with increasing the density of the composites.The analysis of fracture surfaces reveals that fibers and fiber bundles are pulled out in composites,indicating that the composite exhibits a non-linear failure behavior through propagation and deflection of the cracks.展开更多
The 3D orthogonal woven basalt fiber reinforced polyimide (PI) composites were fabricated and characterized in this study. The PI film was firstly prepared to determine PI processing parameters. Fourier transform infr...The 3D orthogonal woven basalt fiber reinforced polyimide (PI) composites were fabricated and characterized in this study. The PI film was firstly prepared to determine PI processing parameters. Fourier transform infrared (FTIR) analysis showed that 300°C was the suitable imidization temperature. Thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) results showed relatively good thermal properties of the PI film. In the fabrication of composites, the multi-step impregnation method was applied. The bending properties of 3 mm-thick composite showed increasing trend in all and the second-time impregnated composite had much higher value than the first-time impregnated composite. Moreover, the bending fracture mode photos showed obvious creases except for the first-time impregnated materials, which agreed well with the bending property values. The dielectric constants for the composites were complex because they had not regular value following the mixing rule of the composites, which was mainly due to the interfacial polarization and other effects in the fabrication processing.展开更多
文摘A combined beam model representing the periodicity of the microstructure and micro deformation of 3D woven composites is developed for predicting mechanical properties. The model considers the effects of off axial tension/compression and bending/shearing couplings as well as the mutual reactions of fiber yarns. The method determining microstructure by using woven parameters is described for a typical 3D woven composite material. An analytical cell, constructed by a minimum periodic section of yarn and interlayer matrix, is adopted. Micro stresses in the cell under in-plane tensile loading are obtained by using the proposed beam model and macro modulus is then obtained by the averaging method. Material tests and a 2D micro FEM analysis are made to evaluate this model. Analyses reveal that micro stress caused by tensile/bending coupling effect is not negligible in the stress analysis.
基金Project supported by the National Natural Science Foundation of China (No.90405015)
文摘A micromechanical model for elastic behavior analysis of angle-interlock woven ceramic composites is proposed in this paper. This model takes into account the actual fabric structure by considering the fiber undulation and continuity in space, the cavities between adjacent yarns and the actual cross-section geometry of the yarn. Based on the laminate theory, the elastic properties of 3D angle-interlock woven ceramic composites are predicted. Different numbers of interlaced wefts have almost the same elastic moduli. The thickness of ceramic matrix has little effect on elastic moduli. When the undulation ratio increases longitudinal modulus decreases and the other Young＇s moduli increase. Good agreement between theoretical predictions and experimental results demonstrates the feasibility of the proposed model in analyzing the elastic properties of 3D angle-interlock woven ceramic composites. The results of this paper verify the fact that the method of analyzing polyester matrix composites is suitable for woven ceramic composites.
基金Project(50872154)supported by the National Natural Science Foundation of ChinaProject(20080431029)supported by China Postdoctoral Science FoundationProject supported by the Postdoctoral Science Foundation of Central South University,China
文摘The 3D fine-woven punctured C/C-(PyC/SiC/TaC)composites,composed of PyC/SiC/TaC interphases and pyrocarbon (PyC)matrix,were synthesized by isothermal chemical vapor infiltration(ICVI)methods.The alternating layers and the structure of these composites were examined by polarized light microscopy(PLM),X-ray diffractometry(XRD)and scanning electron microscopy(SEM).It is found that the PyC matrix has rough laminar(RL)structure,the TaC layer has NaCl-type cubic structure,and the SiC layer has few wurtzite type 10H-SiC besidesβ-SiC structure.The effects of fiber coating and the bulk density on the tensile and flexural properties of composites along X or Y and Z direction were investigated.It is shown that fiber coated 3D woven punctured C/C composites have good tensile and flexural strength,and the maximum of flexural strength is 375 MPa in X or Y direction at density of 1.89 g/cm 3 ,which is about three times higher than that of samples without TaC/SiC fiber coating.The flexural strength and bending strength increase with increasing the density of the composites.The analysis of fracture surfaces reveals that fibers and fiber bundles are pulled out in composites,indicating that the composite exhibits a non-linear failure behavior through propagation and deflection of the cracks.
文摘The 3D orthogonal woven basalt fiber reinforced polyimide (PI) composites were fabricated and characterized in this study. The PI film was firstly prepared to determine PI processing parameters. Fourier transform infrared (FTIR) analysis showed that 300°C was the suitable imidization temperature. Thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) results showed relatively good thermal properties of the PI film. In the fabrication of composites, the multi-step impregnation method was applied. The bending properties of 3 mm-thick composite showed increasing trend in all and the second-time impregnated composite had much higher value than the first-time impregnated composite. Moreover, the bending fracture mode photos showed obvious creases except for the first-time impregnated materials, which agreed well with the bending property values. The dielectric constants for the composites were complex because they had not regular value following the mixing rule of the composites, which was mainly due to the interfacial polarization and other effects in the fabrication processing.
