Interaction analysis between a propagating crack and an interface: Phase field and cohesive surface models

Abstract

The interaction phenomenon between a propagating crack impinging an interface is studied with a phase-field approach in combination with a cohesive surface model. The phase-field technique simulates the crack propagation across the medium, and the cohesive surface model simulates the degradation process of the adhesive interface. The main assessed mechanisms of this interaction are deflection of the crack into the interface, crack penetration, and kink of the crack out an interface. For a specified load system, the occurrence of each mechanism depends on the material fracture properties characterizing the interface and the medium. According to the results obtained using the present approach, we conclude that these interaction modes are ruled by a mixed criterion involving the ratios of toughness and strengths of the medium and the interface. A lower bound for the ratio between the medium and interface strengths exists below which penetration will likely happen independently of the toughness. This conclusion confirms previous studies of interaction reported elsewhere in the literature performed with a different numerical methodology. The apparent increase of the structural toughness due to the crack-interface interaction and the mechanisms leading to this outcome are also analyzed in one specific case. An additional contribution of the paper points to describe a variationally consistent mechanical formulation coupling phase-field and cohesive zone models along with its corresponding numerical algorithm. This formulation provides general jump conditions across the interface of the primal descriptors, in particular, the phase-field continuity conditions across the interface. Specific emphasis is given to analyze the effect that the phase-field continuity conditions induce in the kinking of cracks outs of interfaces. Consequently, and considering that the present phase-field approach is not affected by numerical artifacts coming from the finite element mesh discretization, we assess its potential to capture the crack deviation mechanism out of the interface.