Degradation of SiC/BN/SiC minicomposites in heat-stress-moisture-oxygen coupling environments, I: Static fatigue test study

This study investigates the degradation effects of high-temperature and humid oxygen environments on SiC/BN/SiC minicomposites, potential materials for aerospace and power generation applications. Monotonic tensile tests show minimal influence on initial modulus (E1) and matrix cracking, but significant reductions in modulus (E2) and failure strength occur at 1100 degrees C with 33% water vapor and 33% oxygen, while failure strain decreases at 1200 degrees C. Static fatigue tests reveal two groups based on service life: failure to reach 100 h at 900 degrees C and 1100 degrees C, and achieving 100 h at temperatures above 1200 degrees C. Key mechanisms affecting strength and life in wet oxygen environments are identified, including oxidative healing of matrix cracks, fiber degradation, and BN coating oxidation. This study provides valuable insights into minicomposite behavior in challenging conditions.