The stress state and failure properties of adhesive-bonded plastic/metal joints

Abstract

The stress and strain states in various adhesive-bonded plastic/metal single lap joints under tensile shear loading up to failure have been studied by means of the non-linear finite element method to determine the influences of spew fillets, different adhesives and different metal adherends. The strength and failure properties of these joints have been also investigated based on the numerical and experimental results. The finite element results show that the introduction of spew fillets leads to a significant reduction of peak adhesive stresses, and also to decreased stress and strain concentrations in the adherends in the most critical region. A stiffer adhesive promotes stress and strain concentrations in the overlap end regions of the bonded joints, while the use of an aluminium alloy as the metal adherend instead of steel in a plastic/metal bonded joint can improve the symmetry of adhesive stress distributions due to reduced adherend stiffness imbalance. Experimental joint strengths are shown to correlate well with the stress and strain states in the bonded joints. The validity of the finite element results is confirmed by strain measurements. For the plastic/metal joints investigated, failure takes place in the region of highest strain concentration in the abs plastic adherend as a result of exhaustion of ductility. The maximum accumulative effective plastic strain in the critical region can be used as a parameter for strength prediction of these joints.