Failure prediction of adhesively bonded lap joints between metal and composite adherends

Most of the modern civilian or military aircrafts use advanced composite materials for their primary structural components, in addition to metals. The components are joined together by using either fastener or adhesively bonded joints. But with the introduction of composite materials in aircraft industries, adhesively bonded lap joints are most preferred. This is due to the fact that they develop smooth load transfer and fewer points of stress concentration as compared to fastener joints. The failure prediction of such joints is extremely important, to avoid catastrophic failures during aircraft service period. In the present investigation, an adhesively bonded lap joint between metal-composite (i.e., Al 2024-T3/CFRP) adherends bonded with Redux 319-A adhesive has been analyzed using finite element method considering geometric non-linearity and incorporating adhesive material nonlinear behavior. The failure has been predicted using plastic zone size criterion of adhesive material, which is innovative approach of this study. Also, experimental program is carried out on such joints to correlate with the predicted failure load obtained from numerical model. In this study, the failure of joint is assumed to take place due to adhesive failure only. Plastic zone size in adhesive at failure load of joint is taken as 15 % of the lap length as established from the previous work of the authors. It is observed that the failure load of the adhesively bonded lap joint between composite-metal adherends as obtained from numerical model is well compared with that obtained from experimental study. Results are discussed