Determination of interface fracture toughness of adhesive joint subjected to mixed-mode loading using finite element method

In this study, a compact mixed-mode (CMM) specimen, which comprises an adhesive joint and a loading fixture, is employed to determine interface fracture toughness of an adhesively sandwiched joint with an interface edge crack subjected to global mixed-mode loading. An interface mechanics-based finite element (FE) method is developed to simulate the stress and displacement distributions around the tip of an interface edge crack situated in the sandwiched joint. A small region crack-tip opening displacement (CTOD)-based linear extrapolation method is developed to determine stress intensity factors (SIFs) at the crack-tip. Effect of pre-crack length on the SIFs is studied and a length range of pre-crack is proposed for the determination of SIFs. Furthermore, these methodologies are applied to characterize the critical interface fracture toughness of the sandwiched joint. Three types of fracture criteria, i.e., modes I and II critical fracture toughness-based failure assessment diagram (FAD), effective critical fracture toughness-based failure assessment criterion (FAC), and strain energy release rate-based FAC, are established for the reliability design and failure assessment of the adhesively bonded sandwich joint.