Analytical and experimental investigations of crack propagation in adhesively bonded joints with the Mixed Mode Bending (MMB) test Part I: Macroscopic analysis & Digital Image Correlation measurements

Crack propagation resistance of Hysol®EA9321 toughen epoxy paste under mixed mode loading has been characterized using Mixed Mode Bending set-up. During the crack propagation stationary value of the fracture energy is measured. For finer investigation of the experiment, a phenomenological model consisting of two Timoshenko beams joined with a two parameters elastic foundation is derived to estimate the cohesive stresses distribution along the bondline. Digital Image Correlation measurements are performed together with classical macroscopic force versus deflection measurements which are compared with the displacement field predicted with the model. The evolution of the displacement field in the process zone evidences nonlinear behaviour of the adhesive prior the crack starts to propagate. However, the overall sensitivity of these experimental data is not sufficient to allow precise identification of the interface separation law.