The measurement of damage initiation, particle adhesion and cohesive strength from traction displacement curves of a nano-toughened epoxy

In this work the deformation behaviour of a nano-toughened epoxy adhesive is measured at different levels of stress triaxiality. The test method consists of a notched axisymmetric adhesive layer loaded in tension. The recorded traction displacement curves were analysed numerically and it was found that the measured peak stress corresponds to the intrinsic cohesive strength, σmax of the material. This method allows experimental measurement of σmax for use in cohesive zone models of fracture. Additional features of the traction displacement curves include a kink that corresponds to particle debonding at a critical hydrostatic stress. By application of the Mori–Tanaka model, the relationship between the experimental measurements and particle/matrix adhesion is described.