Modeling of high strength steel joints bonded with toughened adhesive for vehicle crash simulations

Improvement of the structural adhesive increases the difficulties in crash simulations of adhesive-bonded vehicle structures. In this paper, a simplified finite element model is recommended for modeling of the toughened adhesive-bonded joint. Solid elements and shell elements are respectively used to represent the adhesive and the base metal. To better predict the impact response of adhesive, an isotropic elastoplasticity model in LS-DYNA 971 is modified, in which the strain rate effect of both the pre-failure material properties and the failure criterion can be characterized. A method that can correct the variation of adhesive thickness is developed. The input failure parameters of the material model are identified with simulations of adhesive-bonded coach-peel and lap-shear coupon tests. It is found that adhesive failure parameters in the simplified model are independent of the base metal thickness.To improve the simplified model, several issues associated with its practical application, e.g., influence of spewed-out adhesives, variations of adhesive layer representation, have also been addressed in this paper. The recommended simplified model is then used in simulation of the adhesive-bonded tube axial impact test, which validates well its characterization capability and computational efficiency.