Numerical analysis of lap shear joints made of functionally graded materials

The strength and life of adhesively bonded joints can be significantly improved by redistributing the stresses at overlap ends over the bond length. One way to achieve this is by varying the material properties, with the help of so-called functionally graded materials (FGM). In this study, stress transfer mechanics in a joint made of a FGM adherend and a homogeneous, isotropic adhesive are investigated. Damage in the adhesive bonded FGM joints manifests as cohesive and adhesive failures. Some of these damages can simultaneously present in the joint. Therefore, the adhesion failure and their propagation in a curved FGM adherend are studied here. All the simulations are performed in a geometric nonlinear finite element (FE) simulation framework using ABAQUS framework. Loss of structural integrity in a lap shear joint made of FGM adherend with a pre-embedded crack at the interface of adherend and adhesive is modelled, and the load transfer and damage propagation are studied. Furthermore, a parametric study of the structural response by varying the parameters: shallowness angle ( theta) and compositional gradient exponent (n) are also performed. Based on the results, mode-II is observed to be a dominating mode. The debonding from the substrate is found to initiate from the centre when n is the lowest.