Simulation of creep crack growth in ceramic composites

The elevated temperature response resulting from tensile creep of fiber reinforced ceramic composites was modeled using Monte Carlo simulation. The model consisted of a uniaxially loaded fiber tow aligned with the direction of applied load, and modeled the growth of matrix cracks resulting from creep failure of bridging fibers. A creep strain rate consisting of primary and steady state components was assumed, and each component was modeled by a power law relationship. Power law creep exponents in the range of 2.0–2.5 for a selected SiC/SiC system at stress levels ranging from 60 MPa to 200 MPa were evaluated. Fatigue-like behavior was predicted as a result of tensile creep, and a fatigue exponent of 3.03 ± 0.07 was predicted for nominal stress levels less than 200 GPa. The influence of initial crack length on failure lifetime was also studied, but was found to have little influence on the predicted lifetime. The predicted failure response suggested a stress dependent creep process could be used to model experimental data and evaluate the failure mechanism of reinforced composites.