Mechanical properties evolution of SiC_f/SiC composites with a BN/SiC multilayer interface oxidized at elevated temperaturek

In this study, the mechanical properties of SiCf/SiC composites with a BN/SiC multilayer interface was evaluated after oxidized at 800 degrees C, 1100 degrees C and 1400 degrees C for 200 h. The damage evolution of the fabricated and oxidized composites were analyzed by acoustic emission techniques. The chemical composition and structural evolution of the SiCf/SiC composites after oxidation were observed by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and energy dispersive spectroscopy. Significant temperature-dependent strength degradation of the SiCf/SiC composites was observed. The results indicated that the interfacial microstructure change caused by oxidation had a significant impact on the damage process of the composites, and two different degradation mechanisms for oxidized composites are discussed. The toughening mechanism of crack deflection and fiber pull out failed after oxidation at 800 degrees C. The degradation of the mechanical properties after oxidation at 1100 and 1400 degrees C was attributed to the hysteresis of fiber breakage caused by weak interface bonding. This work could predict the service life of SiCf/SiC composites and contribute to their early application in aerospace.