Investigating the influence of material non-linearity in the fracture properties of ductile adhesives submitted to mixed-mode loading

The influence of the mechanical behaviour of a crash optimized adhesive in its fracture properties at different mode ratios in the plane I/II is discussed. The adhesive under investigation has been previously studied by means of standardized TDCB (Tapered Double Cantilever Beam) and MMB (Mixed Mode Bending) tests. In the current study, these tests were modelled numerically considering first the linear elastic case for the adhesive and secondly its non-linear behaviour using a spectral viscoelastic law. The simulations for the non-linear case have been performed under plane strain and plane stress assumptions. Crack initiation and propagation were simulated using cohesive zone modelling. The non-linearity of the adhesive material had minor effect in its fracture response under mode I loading. However, considerable impact has been observed while moving towards the mode II load case, where the fracture energy was calculated almost constant and equal to the one at mode I.