A micromechanics model is employed in the analysis of unidirectional and cross-ply ceramic matrix composites (CMCs) under room-temperature fatigue. The damage mechanisms considered are matrix cracking, fiber/matrix interfacial debonding and slip, fiber fracture and fiber pull-out. The predicted fatigue response is characterized by stress-strain hysteresis, strain ratchetting, modulus degradatio and S-N behavior. For these predictions, the analysis methodolgoy requires the development of (1) micromechanics models to define the laminate's geometry and constitutive relation; (2) failure criteria to estimate the extent of microstructural damage, and (3) a means for analyzing frictional slip (hysteresis), fiber puss-out (strain ratchetting), interfacial wear (degradation of the interfacial shear stress) and laminate failure (S-N behavior).
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