Thermal stability of CVI and RMI SiC/SiC composites adopting Cansas 3303 SiC fibers

The effect of heat treatment on the microstructure and performance of Cansas 3303 SiC fiber bundles and SiC/SiC composites with BN interphase, prepared by CVI or RMI, are investigated. Additionally, the tensile properties and fracture behavior at different temperature of CVI or RMI SiC/SiC composite are examined. Unconstrained SiC fiber bundles stable below 1350 degrees C, halving at 1450 degrees C and further decreasing with temperature rises. In the composites, however, the interphase and matrix exert compressive stress on fibers, mitigating their performance decline. The microstructure of interphase is mainly affected by heat treatment temperature. Tensile strength of both composites decreases with temperature. Both composites maintain structural stability with minimal changes in flexural properties below heat treatment at 1200 degrees C. The flexural strength decreases with further rising heat treatment temperature and time. The mechanisms of properties degradation in both composites are discussed and a method for studying the thermal stability of SiC/SiC composites is established.