A micromechanically based model for damage-enhanced creep-rupture in continuous fiber-reinforced ceramic matrix composites

A micromechanically based model for the mechanical response of unidirectional ceramic matrix composites in creep-rupture (and fast-rupture) conditions is presented. It is based on the model proposed by Halverson and Curtin (2002). The essential physics results from the establishment of the equilibrium conditions – load balance between the applied stress and the stresses carried by the constituent phases – at the matrix-crack planes and at transverse planes “far-away” from the matrix cracks. The analysis incorporates stochastics of fiber-strength, fiber-damage evolution, effects of fiber pull-out and the matrix crack-damage state, under the global load sharing assumption, to predict deformation and lifetime. The proposed model is capable of describing interrelated phenomena that are observed experimentally during creep-rupture in ceramic matrix composites such as the primary and the tertiary creep regimes and the lifetime. Moreover, according to the model, high fiber creep-compliance is found to be desirable in terms of lifetime but not in terms of strain, a result of importance for effective composite design and application in structural components.