Fracture mechanism of adhesive single-lap joints with composite adherends under quasi-static tension

Abstract

Adhesive joints with composite adherends have been widely applied in the automotive and aerospace industry. The demands on high performance adhesive joints highlight the importance of understanding their respective fracture mechanisms. In this paper, single-lap joints (SLJs) bonded with a brittle and a tough adhesive were manufactured and tested, respectively. Experimentally, the fracture mechanisms of the joints were investigated based on failure load, detailed fracture surface observation and images captured by high-speed camera. The results showed that SLJs bonded with the brittle adhesive failed cohesively in the adhesive, while SLJs bonded with the tough adhesive failed by interlaminar delamination in the CFRP. The sandpaper treatment on adherend can cause a intralaminar delamination failure mode of SLJs even if the adherend is stronger than the adhesive. Numerically, finite element models with cohesive zones were built to determine the damage of materials and to validate the fracture mechanisms. The parameters estimated in literature were experimentally tested and varified by a parameter study. Convergent failure load were obtained by a mesh size study for models with and without end-tabs. Both models showed good consistency with the experimental failure load and failure mode.