Virtual Material Testing of Adhesive Joints

Abstract: The automotive industry has shown an increasing interest in adhesive bonding for mixed-material joining. Modern design methods are critically dependent on accurate material models and data for numerical methods to enable the simulation of a design prototype early in the design process. This study proposes a numerical modelling approach to simulate the deformation and failure in adhesive joints subjected to different loading states. The model incorporates the smeared crack method that combines plasticity and damage theories. Linear Drucker-Prager plasticity is coupled with damage formulation for stiffness degradation to model both plasticity and softening. The model validation is performed by comparing the model prediction with experimental test results from Double-Cantilever Beam (DCB) and End Notched Flexure (ENF) fracture tests. The tests have been conducted on adhesive joints with three different adhesive thicknesses. A numerical FE analysis of a Mixed-mode Bending (MMB) test was performed to determine the mixed-mode fracture envelope of the adhesive joint. The path independent J-integral method is used to determine the fracture properties (critical strain energy release rate, Gc) for mixed-mode loading of the adhesive joint. The effect of adhesive thickness on the mixed-mode fracture toughness is investigated. This model complements the existing analytical method used at Volvo Cars to evaluate adhesive strength in CAE as it provides better input data to the existing method without the need for extensive testing.