A life prediction model for metal matrix composites

Global deformation response of metal matrix composites (MMCs) to applied mechanical and thermally induced stresses depends upon (1) the mechanical and thermal properties of the constituent materials, (2) residual stresses in the constituents induced by the composite consolidation process, and (3) the nature and extent of micromechanical damage which may occur and accumulate over time. In the present work, a mechanistic model for predicting time dependent global deformation response of unidirectional metal matrix composite subjected to fiber direction stresses is used in conjunction with several viscoplastic models for the matrix, viz. power law, Bodner-Partom and GVIPS, and compared with laboratory test data. The model incorporates the effect of the micromechanical residual stresses in the fibers and the matrix induced by the composite fabrication process. The model also incorporates the effect of discrete existing and/or progressively occurring fiber damage on global MMC deformation response. The criterion for fiber fractures is based on statistical information on fiber strength. In this work strain predictions obtained using this model are compared with thermomechanical fatigue test data.