On the opening profile and near tip fields of an interface crack between a polymeric hydrogel and a rigid substrate

The opening profile and near tip stress fields of an interface crack between a polymeric hydrogel and a rigid substrate in the plane strain case are studied with the finite element method. The constitutive model proposed by Hong et al. (2008) is implemented by using a user subroutine in ABAQUS to simulate the chemo-mechanical coupling behavior of the hydrogel. Two interface models in front of the crack tip are considered, i.e., a perfectly bonded interface (fully pinned) model and a cohesive interface model. Our numerical results show that, when subjected to a tensile load, the solvent molecules in the hydrogel tend to concentrate around the crack tip and introduce extra swelling, which influences the opening profile and near-tip fields of the interface crack. For the fully pinned interface model, an increase of the free swelling stretch may hinder the flipping over of the crack face. The dominant stress component in front of the crack tip is closely related to the opening profile of the interface crack. The effect of interface damage on the opening profile of the interface crack is also studied in this paper with the aid of the cohesive zone model. Our study indicates that the intrinsic properties of the interface have significant influences on the opening profile of the interface crack.