Evaluation on Failure Resistance to Develop Design Basis for Quasi-Ductile Silicon Carbide Composites for Fusion Application

Silicon carbide composites (SiC/SiC) are promising candidate materials for fusion reactors. For the practical application of this class of materials, a design basis for SiC/SiC composites needs to be developed because of inherent brittle-like fracture, i.e., quasi-ductility, which is totally different from ductility of metals. For this purpose, the failure behavior, i.e., matrix cracking behavior, of a new class of radiation-resistant SiC/SiC composites, e.g., a nano-infiltration transient-eutectic phase (NITE) SiC/SiC composites, was evaluated. The single-edge notched bend test results identified notch-insensitivity of the composites regardless of the specimen size. This suggests an apparent correlation between stress and energy criterions, possibly eliminating a parameter required for the mechanical property database development. According to this fact, a fracture resistance as an energy parameter for failure analysis of the composites has been developed based on the nonlinear fracture mechanics. A preliminary model could separately distinguish contributions of micro-cracking from macro-crack formation energy. Good crack resistance of pilot-grade NITE-SiC/SiC composites was finally demonstrated.