Effect of temperature on cohesive modelling of 3M Scotch-Weld™ 7260 B/A epoxy adhesive

This work addresses the effect of the test temperature on the cohesive model parameters for the 3M Scotch-Weld((TM)) 7260 B/A epoxy adhesive. It extends a previous experimental work done at room temperature and further develops a previously proposed parameter identification method based on optimization. Double-Cantilever Beam (DCB) and End-Notched Flexure (ENF) tests were conducted at four different temperatures: 20 degrees C, 40 degrees C, 55 degrees C and 70 degrees C. Moreover, Single Lap Joints (SLJ), and bulk specimens' tensile tests were carried out. Finite element analyses of DCB and ENF tests were performed and optimization algorithms were used to calculate constitutive cohesive model parameters. Three approaches were followed. First, cohesive parameters were derived from bulk tests. Then, optimization with two variables for each mode was conducted, to identify the parameters e(i) and sigma(u,i) (i = I, II) of a triangular traction separation law. In the third, only sigma(u,i), was taken as variable, while e(i) was derived from the elastic modulus of the bulk adhesive. Finally, the cohesive models were applied to simulate the response of the SLJ, and numerical results were compared with experiments. The two free variables optimization method allowed to obtain the most accurate predictions of the maximum load and SLJ displacement at failure.