Subcritical crack growth in CVISiCf/SiC composites at elevated temperatures: Effect of fiber creep rate

Subcritical crack-growth studies in SiCf/SiC composites were conducted with composites reinforced with Hi-Nicalon fibers over a broad temperature rang e for comparison to earlier studies on materials reinforced with Nicalon-CG fibers. Composites with a 0/90 plain weave architecture and carbon interph ase were tested in argon from 1173 to 1473 K. Crack growth data obtained in inert environments are consistent with a proposed fiber-creep-controlled c rack-growth mechanism. Measured crack-growth activation energies and time-t emperature exponents in argon agree with fiber creep-activation energies an d nonlinear creep equations for both fiber types. Estimates of local strain s during crack growth are in reasonable agreement with estimated fiber cree p strains for the given times and temperatures. The increased creep resista nce of Hi-Nicalon fibers is reflected in reduced crack-growth rates for com posites containing those fibers. (C) 2001 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.