Abstract: Continuous silicon carbide fiber reinforced silicon carbide composites (SiC_f/SiC) are widely utilized in the hot-end components of aero engines due to their exceptional properties and high-temperature resistance. To ensure the safety and reliability of SiC_f/SiC composite parts during service, it is crucial to investigate the evolution of their mechanical properties under prolonged high-temperature exposure. In this study, mini-SiC_f/SiC composites with BN interface were fabricated using Cansas-II SiC fibers. These mini-SiC_f/SiC composites underwent heat treatment at 1100, 1200, and 1350 °C for durations of 5, 10, 50, 100, and 200 h, respectively, to examine the effects of high-temperature and long-term heat treatment on their mechanical properties and microstructure. The results show that at 1100 °C, heat treatment has no significant impact on the mini-SiC_f/SiC composites. The mechanical properties remain largely unchanged, and the contribution fractions of each stage to the overall mechanical performance remain consistent. At 1200 °C, short-term heat treatment shows minimal effects on the mini-SiC_f/SiC composites, with no notable change in tensile strength, However, prolonged heat treatment leads to damage in the SiC fibers, thereby decreasing its tensile strength. At 1350 °C, heat treatment significantly improves the properties of the BN interface but causes severe damage to the SiC fibers, resulting in a marked decline in the mechanical properties of the mini composites. As the heat treatment duration increases, the extent of fiber damage intensifies, leading to a continuous deterioration in the mechanical performance of the composites.

Key words: Cansas-II SiC fiber, mini-SiC_f/SiC composites, heat treatment, acoustic emission, saturated matrix crack spacing