EFFECT OF RESIDUAL-STRESSES ON THE INTERFACIAL FRACTURE-BEHAVIOR OF METAL-MATRIX COMPOSITES

The fiber/matrix interface plays a critical role in the mechanical beh avior of the composites. The fiber push-out test is increasingly being used to characterize the interfacial behavior of metal-matrix composi tes (MMCs). A fracture mechanics approach is used to examine the inter facial debonding process in MMCs and ceramic-matrix composites (CMCs) during a fiber push-out test. The equivalent domain integral (EDI) met hod is implemented in a finite element code and is used to compute the strain-energy release rates for the interface crack. The cooling proc ess from the composite consolidation temperature, specimen preparation for the push-out test and the actual testing are included in the fini te element simulation. A strain-energy-based debonding criterion is us ed to predict the interfacial behavior. The experimentally observed ph enomenon of bottom debonding in MMCs is explained from the energy rele ase rate variation for the loaning and support end cracks. It is shown that processing-induced residual stresses significantly affect the in itiation and propagation of interface cracks. The advantage of the EDI method over conventional methods for modeling interface crack propaga tion, by eliminating the need for singular elements and thus remeshing with crack advance is demonstrated through the simulation of the push -out test. (C) 1997 Elsevier Science Limited.