高温处理对3D C/SiC复合材料热膨胀性能的影响

研究了不同高温处理前后3D C/SiC复合材料热膨胀系数(CTE)的变化规律,从材料内部热应力变化及结构改变的角度定性地分析了其变化机理。研究发现,3D C/SiC复合材料的热膨胀系数受界面热应力的影响,其变化规律是纤维和基体相互限制、相互竞争的结果;高温处理可提高材料的热稳定性,并通过改变界面热应力及材料内部结构,来影响材料热膨胀系数的变化规律;通过增加基体裂纹来降低复合材料的低温热膨胀,但不影响其变化规律;通过改变材料内部结构,使热应力发生变化并重新分布,对复合材料的高温热膨胀产生显著影响。但高温处理没有改变3D C/SiC复合材料的基体裂纹愈合温度(900℃)。 

EFFECTS OF HEAT TREATMENT ON THERMAL EXPANSION OF 3D C/SiC COMPOSITES

3D C/SiC composites with PyC interlayer were fabricated by low pressure chemical vapor infiltration(LPCVI). The different expansion behavior of the composites was qualitatively analyzed before and after different heat treatments. The results show that the expansion behavior of 3D C/SiC composites, which was affected by interfacial thermal stress, can be regarded as the result of interaction of fibers and matrix. The thermal expansion behavior of the composites is changed after heat treatment due to the increase of thermal stability and the change of thermal stress and microstructure of the materials. The coefficient of thermal expansion (CTE) of the composites is decreased by the increase of matrix cracks at low temperatures and changed by the redistribution of thermal stress at high temperatures. However, the matrix cracks sealing temperature was not changed by heat treatment.