Experimental study and numerical modeling of ENF scheme: Comparison of different beam approaches

In the present paper five beam models are presented to reproduce the experimental response of the End Notch Flexure (ENF) test. In particular, a specific ENF scheme is considered; it is made of two symmetric laminates partially bonded by a adhesive layer, whose thickness is not negligible. The failure occurs at the interface between one laminate and the adhesive, leading to an unsymmetrical failure; moreover, because of the presence of the adhesive layer, the two arms representing the initial defect of the ENF are not in contact. The experimental setup is described and five beam models are introduced to simulate the nonlinear response of the ENF scheme, characterized by an increasing improved kinematics. Failure is studied considering both linear and nonlinear elastic fracture mechanics, introducing in the latter case a very simple cohesive interface model. Solutions obtained by the five beam models are compared with the ones recovered with finite element (FE) analyzes and with the results of the experimental tests, remarking the reliability, the simplicity and the computational efficiency of the beam schemes. It is found that the improved kinematics and the cohesive fracture evolution play an important role in accurately reproducing the response of the ENF scheme.