Evaluation of fracture toughness of MMC interfaces using thin-slice push-out tests

A fracture mechanics based approach is used to compute residual and interfacial fracture energies of some MMC and CMC systems during push-out tests. The phenomenon of bottom debonding in MMC thin slice specimens is examined using experimental results and strain energy computations. Residual stress predictions are correlated with experimentally reported values. The main contribution to the interfacial fracture toughness in MMCs is found to be from the residual stresses and thus the values of G_ir can be considered as a lower bound for the critical strain energy release rate of the interface G_ic. This factor is also demonstrated in the push-out test simulations for pre-strained specimens, where in the absence of residual stresses, a far higher push-out load is necessary for the same critical strain energy release rate; consequently no fiber push-out is observed at lower loads. Interface fracture toughnesses for certain typical MMC and CMC systems are predicted using the developed methodology.