Experimental and numerical investigation of the fracture behavior of adhesive shear tests single lap joints

This work aims to establish a finite element model to simulate the behavior in cracking failure of a shear test of a single lap joint. The interest of having a satisfactory finite element model is to be able to use it to simulate the cases that have not been the subject of experimental tests. A cohesive zone model (CZM) was used to model the propagation of cracks in bonded joints, using a bilinear traction–separation law implemented in the finite element code Abaqus. The cohesive zone is represented by a row of cohesive elements where the progression of the crack will take place. The parameters of the cohesive law of an adhesive “Adekit A140” were determined by fracture tests, performed on DCB and ENF tests. A damage initiation criterion and a mixed-mode failure criterion are used, respectively, to initiate and perform damage to the interfaces. Two numerical models of single lap joint were tested. In the first model (CZMi), the cohesive zone is represented by a row of cohesive elements placed along a single interface (adhesive–substrate) and the second interface of the model being left intact. In the second model (CZMii), the cohesive elements are placed along the two interfaces of between adhesive and substrate. In this case, the cohesive zone comprises two rows of cohesive elements. Experimental shear tests were performed on single lap joints bonded with Adekit A140 adhesive to determine the force–displacement curve. The numerical model using a single row of cohesive elements has a force–displacement curve shifted backward of the experimental force–displacement curve. It shows a greater initial rigidity and less resistance to crack propagation in the joints. The force–displacement curve of the numerical model using two rows of cohesive elements coincides with the experimental force–displacement curve. The numerical force–displacement curve shows good initial stiffness and good resistance to crack propagation in joints. These latest numerical results (two rows of cohesive elements) are in good agreement with the experimental results and allow us to validate the numerical model applied to shear tests of bonded joints.