Mixed mode fracture analysis of adhesive lap joints

A Cherepanov-Rice J integral is derived for Goland-Reissner type joints. It is shown that the resulting J integral is path independent under the assumption of small rotation of adherents and thin adhesive thickness. It represents the product of strain energy density at the edge of the joint and adhesive layer thickness regardless of the mechanical properties (elastic or elastoplastic) of adherents and adhesive. For long overlap elastic joints, the J integral is independent of adhesive thickness and adhesive mechanical properties, and can be estimated simply by a beam model. Load phase angles for a cohesive crack and an adhesive crack are given allowing one to determine the critical load if the corresponding toughnesses are known.