Evaluation of interfacial fracture toughness of MMCs using a computational approach

The fiber-matrix interface plays a critical role in the mechanical behavior of the composites. Fiber push-out test is increasingly being used to characterize the interfacial behavior of MMCs. In this paper, fracture mechanics approach is used to examine the interfacial debonding process in MMCs and CMCs during fiber push-out tests. The Equivalent Domain Integral (EDI) method is implemented in a finite element code and 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 all included in the finite element simulation. A strain energy based criterion is used to predict interfacial debonding. It is shown that processing induced residual stresses significantly affect the initiation and propagation of interface cracks. The experimentally observed phenomenon of bottom debonding in MMCs is explained from the energy release rate variation for the loading and support end cracks. The advantage of the EDI method over conventional methods for modeling 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.