Abstract
Crack deflection in the adhesive layer was investigated for adhesively bonded single lap joints. Cracks occurring at both bond termini interfacially propagated about 0.4 〜 1.4mm (critical length: a_1) away from the lap ends. When the cracks grew to a_t in length, they changed their direction into adhesive layer and propagated cohesively. The stress distribution for various geometric configurations of single lap joints was analyzed by using FEM. A local mix-mode ratio between Mode I and Mode II for interfacial cracks was defined based on the strain energy release rate for each mode. The FEM results show almost the same G_T curves for any geometry of single lap joints if the cracks were supposed to propagate interfacially. The calculated results also showed that the Mode I component in G_T was decreased when the cracks changed their direction. The crack deflection mechanism is related to the change of mix-mode ratio in G_T.
