纤维编织结构对碳纤维增强碳化硅复合材料热膨胀和热扩散系数的影响

EFFECTS OF FABRIC ARCHITECTURES ON THE THERMAL EXPANSION COEFFICIENT AND THE THERMAL DIFFUSIVITY OF CARBON FIBER REINFORCED SILICON CARBIDE COMPOSITES

分别采用热膨胀仪和激光脉冲热导仪测量了2维、2.5维和3维纤维编织结构的碳纤维增强碳化硅(carbon fiber reinforced silicon carbide,C/SiC)复合材料从室温到1400℃温度范围内纵向和横向热膨胀系数,以及厚度方向的热扩散系数。用扫描电镜、光学显微镜观察了样品的微结构。结果表明:低温段(700℃以下),3种C/SiC的纵向和横向热膨胀系数均随温度的升高而缓慢增大,并在700℃之后出现不同程度的波动;高温段(700℃以上),它们的纵向热膨胀系数和2维C/SiC的横向热膨胀系数随温度的升高而减小,而2.5维和3维C/SiC的横向热膨胀系数则随着温度的升高而迅速增大。三者厚度方向的热扩散系数均随温度的升高而减小,3维C/SiC的热扩散系数最大,分别是2.5维C/SiC和2维C/SiC的1～1.2和1.4～2倍。

The thermal expansion coefficient and the thermal diffusivity of 2 dimensional （D）, 2.5D and 3D carbon fiber reinforced silicon carbide （C/SiC） composites were tested from room temperature to 1 400℃ using a thermal dilatometer and laser flash apparatus. The microstructure was observed by scanning electron microscopy and light microscopy. The results show that at low temperature （below 700℃）, the longitudinal and transversal thermal expansion coefficients of all these C/SiC composites increase slowly as the temperature increases, followed by fluctuations of different degrees after 700 ℃. At high temperature above 700℃, the longitudinal thermal expansion coefficients of all these materials and the transversal coefficient of the 2D C/SiC composite decrease as the temperature increases, but the transversal thermal expansion coefficients of the 2.5D and 3D C/SiC composites increase sharply as the temperature increases. The thermal diffusivity of all these composites decreases as the temperature increases, and the thermal diffusivity of the 3D C/SiC composite is the highest, it is 1-1.2 and 1.4-2 times higher than the 2.5D and 2D C/SiC composites respectively.