Room and elevated temperature tensile properties of single tow Ni-Nicalon, carbon interphase, CVI SiC matrix minicomposites

Single tow Hi-Nicalon, C interphase, CVI SiC matrix minicomposites were tested in tension at room temperature, 700, 950, and 1200°C in air. Monotonic loading with modal acoustic emission monitoring was performed at room temperature in order to determine the dependence of matrix cracking on applied load. Modal acoustic emission was shown to correlate directly with the number of matrix cracks formed. Elevated temperature constant load stress-rupture and low-cycle fatigue experiments were performed on precracked specimens. The elevated temperature rupture behavior was dependent on the precrack stress, the lower precrack stress resulting in longer rupture life for a given stress. It was found that the rupture lives of C-interphase Hi-Nicalon minicomposites were superior to C-interphase Ceramic Grade Nicalon minicomposites and inferior to those of BN-interphase Hi-Nicalon minicomposites.