Experimental and numerical analysis of the fracture envelope of composite adhesive joints

To increase the confidence in the design of adhesive structures, it is necessary to accurately predict their strength and fracture properties (critical strain energy release rate in tension, G_IC, and shear, G_IIC). It is of great importance the perception of fracture under mixed-mode, namely in which relates to the strain energy release rate in tension, G_I, and shear, G_II. This allows choosing the best failure criterion to use in cohesive zone models (CZM), to predict the joints’ behaviour. This work presents an experimental and numerical study using the Single-Leg Bending (SLB) test on bonded specimens to obtain the mixed-mode fracture properties. The analysis of G_I and G_II obtained during the experimental phase were addressed. Framing the obtained values in several fracture envelopes enable to select which failure criterion is more appropriate for each adhesive. In the numerical simulations it was possible to reproduce the observed behaviour of the experimental tests, with a positive validation of the chosen propagation criteria.