Effect of residual stresses on the interfacial fracture behavior of metal-matrix composites

The fiber/matrix interface plays a critical role in the mechanical behavior of the composites. The fiber push-out test is increasingly being used to characterize the interfacial behavior of metal-matrix composites (MMCs). A fracture mechanics approach is used to examine the interfacial debonding process in MMCs and ceramic-matrix composites (CMCs) during a fiber push-out test. The equivalent domain integral (EDI) method is implemented in a finite element code and is used to compute the strain-energy release rates for the interface crack. The cooling process from the composite consolidation temperature, specimen preparation for the push-out test and the actual testing are included in the finite element simulation. A strain-energy-based debonding criterion is used to predict the interfacial behavior. The experimentally observed phenomenon of bottom debonding in MMCs is explained from the energy release rate variation for the loading and support end cracks. It is shown that processing-induced residual stresses significantly affect the initiation and propagation of interface cracks. The advantage of the EDI method over conventional methods for modeling interface crack propagation, by eliminating the need for singular elements and thus remeshing with crack advance is demonstrated through the simulation of the push-out test.