Thermophysical And Mechanical Properties Of 2.5D C/SiC Composites

2.5D C/SiC composites arc a new kind of thermostructure material. 2.5D C/SiC composites are composed of layers of straight weft yarns and a set of sinusoidal warp yarns, with the adjacent layers of weft yarns interlaced together by warp yarns. So it has good interlaminar integrate and transverse mechanical property. 2.5D C/SiC composites is only choice of component with one end hermetical (as nose), and it will be widely used in astronautics fields. A systemic and in-depth study on thermal physical property and mechanical property of the composites is important, in order to design the composites and component, and also is necessary of composites application.These papers study the relationship between the coefficients of thermal expansion and temperature, and the relationship between the coefficients of thermal diffusivity and temperature. Then the influence of perform structures, heat treatment, SiC coating and tension test on thermal physical property has been analyzed. Meanwhile, the mechanical property of 2.5D C/SiC composites in room temperature and 1300℃ has been tested, and the relationship between mechanical property and perform structure has been studied. The main contents and results of this work are as follows:1. The thermal expansion coefficients (CTE) of 2.5D C/SiC composites increase slowly as temperature increase from room temperature to 1400℃ CTE of the transverse sample fluctuate between 2×10^-6 /K and 8×10^-6/K; CTE of the longitudinal sample fluctuate between 2×10^-6 /K and 4×10^-6 /K. After the tension test, the cracks of 2.5D C/SiC composites are more than that of as-prepared, therefore CTE of the composites are lower. The heat treatment increases thermal stability. Because of the different perform structures, longitudinal CTE of 2.5D C/SiC composites are the lowest, and its transverse CTE are between that of 2D and 3D C/SiC composites.2. The coefficients of thermal diffusivity (CTD) decrease as temperature increase from room temperature to 1400℃. The CTD of 2.5D C/SiC composites arc fluctuate between 0.056 cm²/s and 0.023 cm²/s. The CTD of the composites with SiC coating increase by 1-2 times compared to the material without SiC coating. After the tension test, the cracks increase the thermal resistance, so the CTD of the composites decrease. Because of the different perform structures, the CTD of 3D C/SiC composites arc the highest, while the CTD of 2.5D are between that of 2D and 3D composites.3. In room temperature, the longitudinal and transverse intensile strength of 2.5D C/SiC composites arc 326MPa and 146MPa; the longitudinal and transverse flexural...