An explicit cohesive element combining cohesive failure of the adhesive and delamination failure in composite bonded joints

Delaminations can change the mechanical behaviour of bonded joints significantly in crash simulations. A cohesive element is presented that enables the simulation of delamination failure in bonded joints on a full scale structural level. The principle of the approach is to compute the through thickness stresses of the adherends analytically within the cohesive element representing the cohesive behaviour of the complete adhesive. Via a stress based interaction criterion it becomes possible to detect delamination in the adherends. The delamination failure is implemented by an adaptation of the cohesive law.The new cohesive element is validated numerically by a single lap joint geometry. The results show good correlation with a conventional cohesive zone modelling when cohesive failure of the adhesive occurs. It can well predict the delamination initiation and approximates the joint strength conservatively. The convergence behaviour of the model is improved. The numerical efficiency is high and enables a representation of both cohesive failure of the adhesive and delamination failure on a structural level.