Abstract
This study investigates the problem of applying fracture mechanics to evaluation of the strength of adhesive joints, focusing on mixed mode fracture criteria. Various types of adhesive joint specimens with a crack in an adhesive layer were prepared for the static tests and fatigue tests. The adherend was acryl plate and epoxy plate and the adhesive was cemedine 1500 and EP-007. The energy release rates GI and GII for various adhesive joints were analyzed by FEM and modified virtual crack extension method. Comprehensive mixed mode conditions from pure mode I to nearly pure mode II were realized in this study. The fracture toughness results obtained showed a mixed mode fracture criterion peculiar to adhesive joints, which can be characterized by GI and GII. It was found that the fatigue crack growth rate in various adhesive joints can be well characterized by the total energy release rate range ΔGT. Therefore, different approaches are necessary for the fatigue crack growth and fracture toughness of adhesive joints under mixed mode conditions.
