Crack growth in adhesive joints

Chapter B.3 presents a research work aiming at a better understanding of the critical strain energy release rate of adhesive joints. The tapered double cantilever beam (TDCB) test measures the work per area of crack, G Ic , which is required for crack growth under mode I loading. This standard test provides no information about the particular way this energy is dissipated, e.g. to create new surfaces and to deform the adhesive layer. Two new methods are presented which aim at the improvement of the understanding of energy dissipation during crack growth. The first approach uses finite element simulations of the TDCB test based on a material model identified from tensile tests. It allows separating the work required for plastic deformation of the major part of the adhesive layer from the work required for the crack growth and the deformation of the adhesive in the immediate vicinity of the crack. The second method adds the measurement of the adhesive surface temperature by an infrared camera to the TDCB test. It shows the thermo‐elastic effect in the adhesive layer as well as heat generation close to the crack. The results of the two investigations are combined to create a first estimate of an energy balance of the TDCB test. The application to a ductile epoxy adhesive shows the feasibility of the proposed methods.