Room and elevated temperature tensile properties of single tow Hi-Nicalon,carbon interphase, CVISiC matrix minicomposites

Single tow Hi-Nicalon(TM), C interphase, CVI SiC matrix minicomposites were tested in tension at room temperature, 700, 950, and 1200 degreesC in air. Monotonic loading with modal acoustic emission monitoring was performed at room temperature in order to determine the dependence of matrix cracking o n applied load. Modal acoustic emission was shown to correlate directly wit h the number of matrix cracks formed. Elevated temperature constant load st ress-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(TM) minicomposites were superior to C-interphase Ceramic Grade Nic alon(TM) minicomposites and inferior to those of BN-interphase Hi-Nicalon(T M) minicomposites. (C) 2000 Elsevier Science Ltd. All rights reserved.