Effects of Matrix Cracking on the Creep of SiC-SiC Microcomposites

The creep behavior of SiC/C/SiC microcomposites at 1200-1400°C and 140-450 Mpa was investigated in the presence and absence of matrix cracking. The microcomposites consisted of single Hi Nicalon fibers coated with a CVD carbon interlayer and a CVD SiC matrix. Since the fibers and matrix had been examined by the same experimental technique, direct comparisons of the creep of the composite and of the constituents were performed. The creep of uncracked microcomposites was successfully modeled using a simple rule of mixtures algorithm. When matrix cracks were present, the microcomposites were modeled using a series composite consisting of intact microcomposite, exposed fiber at the matrix crack, and the debonded region between these first two regions.