Subcritical crack growth in CVI SiCf/SiC composites at elevated temperatures: effect of fiber creep rate Original Research Article

Subcritical crack-growth studies in SiCf/SiC composites were conducted with composites reinforced with Hi-Nicalon fibers over a broad temperature range for comparison to earlier studies on materials reinforced with Nicalon-CG fibers. Composites with a 0/90 plain weave architecture and carbon interphase were tested in argon from 1173 to 1473 K. Crack growth data obtained in inert environments are consistent with a proposed fiber-creep-controlled crack-growth mechanism. Measured crack-growth activation energies and time–temperature exponents in argon agree with fiber creep-activation energies and nonlinear creep equations for both fiber types. Estimates of local strains during crack growth are in reasonable agreement with estimated fiber creep strains for the given times and temperatures. The increased creep resistance of Hi-Nicalon fibers is reflected in reduced crack-growth rates for composites containing those fibers.