Abstract :
Ceramic matrix composites at high temperatures exhibit time-dependent behavior due
to fiber creep, even though the matrix remains elastic. The time-dependent behavior of bridged
cracks for such materials is modeled using a bridging law developed previously which describes the
effects of fibers bridging a matrix crack and accounts for frictional sliding between the fibers and
the matrix. Approximations which simplify the bridging law are presented for short cracks or high
loads. In particular, regimes are identified where the history-dependence of the crack opening rate
can be neglected. Using a simplified form of the bridging law, results are presented for the general
evolution of bridged stationary cracks. Determination of the bridging stress profile at a given instant
in time allows calculation of the crack tip stress intensity factor as a function of time, leading to
estimates for the time to initiate time-dependent crack growth. The results indicate that for very
high loads and very short cracks, a simple form of bridging law can be used to produce accurate
estimates for the initiation time to begin growing matrix cracks. © 1997 Elsevier Science Ltd. All
rights reserved.
