Phase-field modelling of cohesive interface failure

A cohesive interface model is proposed in the framework of the phase-field approach. The discrete interface is transformed into a smeared interface by a regularisation strategy. Nevertheless, the fracture energy is made dependent on the displacement jump, which is approximated by a first-order Taylor expansion of the displacement at the interface. Its value relies on a proper choice of the distance parameter from the interface. We have derived an optimal distance parameter from the analytical solution of a uniaxial tension problem. The accuracy of the approach for cohesive interface modelling is validated in a one-dimensional numerical test and is demonstrated by two examples, including a 'H'-shaped plate and a fibre embedded in an epoxy matrix, featuring straight and curved interfaces.