Crack propagation under mode II dominance at stainless steel–epoxy interfaces with residual stresses and micro-scale roughness

• Crack propagation along a realistic micro-roughness was simulated.
• Fracture at grain boundary grooves was studied using atomic force microscopy.
• A comparison to fracture testing indicated 100-fold toughening mechanism.
• Voids, modelled at grain boundaries, decreased the critical strain by 16%.

This report describes investigations of grain boundary groove effects on mode II dominated interface fracture. The study focused on a specific interface between stainless steel and an epoxy adhesive. First, a finite element model was developed to simulate residual stresses and crack propagation. Second, the simulation results were compared with the experimental results from a previous study (Kanerva et al., 2013. Eng. Fract. Mech. 99, 147-158). Additional measurements were performed using atomic force microscopy. Based on the simulation, a 100-fold toughening effect due to the grain boundaries was determined. Implementation of flaws, in the form of interfacial voids, decreased the toughening effect by 35% and increased the mode II dominance significantly. The work underlines the practical importance of complete wetting by the adhesive and its necessary adherence to the grain boundary groove walls.

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