Tensile and low-cycle fatigue behaviors of a SiC/SiC composite at elevated temperatures in air

Isothermal tensile and low-cycle fatigue (LCF) tests were conducted on a two-dimensional 2D woven SiC-fiber-reinforced SiC-matrix (SiC/SiC) composite with Sylramic™-iBN SiC fibers at 1200, 1300, and 1400 °C in air. The composites were fabricated by polymer infiltration and pyrolysis (PIP), which yielded a crystalline (SiC+Si 3 N 4 ) matrix. The tension-tension LCF tests were performed with peak stresses ranging from 103 to 173 MPa at an R-ratio of 0.05 and a frequency of 0.333 Hz for up to 2.71 × 10 5 runout cycles or failure. The specimens that survived runouts were tensile tested at the fatigue testing temperature, and the results were compared with the baseline in-plane tensile properties of as-fabricated composites. Prior fatigue testing caused reduction in both primary elastic modulus and ultimate tensile strength. Fracture surfaces and cross-sectional microstructures of the specimens that failed during tensile and fatigue tests were analyzed to determine failure modes and damage mechanisms.