Debonding-on-demand of vacuum-infused thermoplastic fibre-reinforced laminates with improved recyclability

Debonding-on-Demand (DoD) is key in enabling recyclability and modular design of lightweight composite structures. This work investigates the effectiveness of DoD mechanisms using resistive heating modified substrates and thermally expandable particles (TEPs) on structural adhesive bonding. Methyl methacrylate adhesives are applied on vacuum-infused thermoplastic GFRP laminates with an Elium© acrylic matrix. Characterisation includes thermal imaging, DSC, lap-shear testing and fracture surface analysis. To enable localised thermal DoD-triggering, modified substrates are fabricated with integrated resistive heating elements. Thermal stimulus is applied either externally (via oven) and locally (via resistive heating). The expansion of TEPs is confirmed by optical microscopy. The most effective DoD response occurs in specimens with modified substrates without TEP, attributed to significant softening of the adhesive above its glass transition temperature. Specimens with both structural adhesive and TEP show a moderate DoD effect, though the reference strength is lower due to TEP-induced disruptions within the adhesive. Externally heated triggering of TEP yields little DoD effect. Fracture surface analysis supports these findings, showing characteristic changes consistent with adhesive softening and cohesive strength reduction. Results highlight how the incorporation of localised resistive heating elements can allow an easier recycling and reversible joining, which contrary to TEPs, can be repeated.