This paper presents a strategy towards achieving thermoplastic adhesive tapes with high toughness by microstructuring conventional tapes using tailored defects. Toughened tape was manufactured using two layers of a conventional tape where the bondline between the two adhesive layers was microstructured by embedding tailored defects with specific size and gap between them using PTFE film. Mode I toughness of the toughened tape was characterized experimentally. A high-fidelity finite element model was implemented to describe the toughening mechanisms using double cantilever beam simulations and end notch flexural tests. The model considers for the plasticity of the adhesive layer, the decohesion at the adherend-adhesive and adhesive-adhesive interfaces and progressive damage inside the adhesive layer. The adhesive-adhesive interface with the tailored defects inside the adhesive layer enables crack migration between adherend-adhesive interfaces, crack propagation at adhesive-adhesive interface, backward crack propagation under the defect, and plastic deformation of the adhesive ligament. The maximum toughness improvement of the tape with tailored defects of equal width and gap between two successive defects of 2 mm reached 278% and 147% for mode I and II, respectively, compared to conventional tape.
Keywords: adhesive joints; damage mechanics; fracture toughness; modeling; thermoplastic adhesive tapes.