Plastic yielding of a film adhesive under multiaxial stresses

This article presents a study of the plastic yielding behaviour of a rubber-toughened film adhesive (FM73) subjected to triaxial stresses. Experiments were carried out using a bonded joint specimen similar to the Iosipescu specimens originally designed for use with fibre composite materials. The experimental results reveal that the plastic yielding of the FM73 adhesive exhibits a complex dependence on the hydrostatic stress, especially in the compression regime. It is found that the conventional yield criteria widely employed to model adhesives, such as the modified Tresca criterion, the modified von Mises criterion, and the linear Drucker-Prager criterion, are unable to characterise the yield locus. To overcome this difficulty, the modified Drucker-Prager/cap plasticity model that is commonly associated with geological materials is adopted in the present study, which provides a good correlation with the experimental data.