A crack impinging upon an interface that can debond and then offer frictional resistance is studied theoretically. The central question at issue is the level of the remote load at which the crack penetrates the interface, whether or not some debonding of the interface occurs first. To answer this question, we compute the stress enhancement experienced by the impinged material—averaged over a microstructural length such as the fiber diameter—as a function of interface parameters. The solution to this elasticity problem is arrived at by means of distributed dislocations to represent relative motion at the interface. Special care needs to be taken to account properly for the contact problem at the interface. Not unexpectedly, it is found that higher debond energies and greater frictional resistances lead to higher stress concentrations and, hence, to lower remote failure loads.

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