Damage tolerance of an architected adhesive joint

•Adhesive joints with square-wave interface architecture were fabricated and tested.•Hysteresis (the “Mullins effect”) was observed for a rubber-like adhesive.•Square-wave joints were modelled as combinations of tensile and shear joints.•A design map predicts strength, toughness and damage tolerance of square-wave joints. Butt joints have been manufactured from aluminium alloy substrates of interlocking square-wave architecture and silyl-modified polymer (SMP) adhesive. The macroscopic traction versus opening separation responses of the butt joints have been measured for selected values of square-wave amplitude and thickness of adhesive layer. Insight into the failure mechanisms of the square-wave joint is obtained by performing tensile tests on planar butt joints and by performing double-lap shear tests on planar joints. The mechanisms of adhesive failure in a planar butt joint are determined by micro X-ray computed tomography. It is determined by optical fractography that the failure mechanisms in the square-wave joint are a combination of those observed in the butt and double-lap shear joints, and consequently a simple model for the strength and toughness of the square-wave joint is developed. A design map is constructed for the strength, toughness and damage-tolerance of the square-wave micro-architecture in order to generate the optimal topology for a given application.