Interaction between adherend plasticity and adhesive damage in metal/composite joints: application to bonded composite repair of metallic structures

The plasticity in the crack region is a great influence on the fatigue life of aircraft structures, and the adhesive damage has negative effects on the durability of bonded joints. In this paper, the interaction effect between the crack tip’s plasticity and adhesive damage in a bonded composite repair of cracked metallic panels was analyzed using the three-dimensional finite element (FE) method. A damage criterion was implemented in the FE model to evaluate the damaged zone in the adhesive layer, and the plastic strain around the crack was extracted from the FE calculations. In this research, we have demonstrated that the applied load has very significant effects both on crack plasticity and adhesive damage, but the ductility of the repaired material has no significant effect on adhesive failure. Fatigue tests and SEM observations were performed to validate the numerical results.