Subcritical crack growth in CVISiCf/SiC composites at elevated temperatures: Dynamic crack growth model

A dynamic crack-growth model has been developed to predict slow crack growt h in ceramic composites containing nonlinear, creeping fibers in an elastic matrix. Mechanics for frictional bridging and nonlinear fiber-creep equati ons are used to compute crack extension dynamically. Discrete, two-dimensio nal fiber bridges are employed, which allows separate bridge "clocks", to c ompute slow crack-growth rates for composites containing Nicalon-CG and Hi- Nicalon fibers. Predictions for activation energies, time-temperature expon ents, crack lengths, and crack-velocity data for composites in bending at 1 173 K to 1473 K in inert environments are in good agreement with experiment al data. In addition, calculated creep strains in the bridges agree with ex perimental damage-zone strains. The implications of multiple-matrix crackin g are discussed. (C) 2001 Acta Materialia Inc. Published by Elsevier Scienc e Ltd. All rights reserved.