Reversible Fusion Bonding of Vacuum-Infused Thermoplastic Composites via Integrated Resistance Heating

This investigation presents a reversible fusion bonding approach for vacuum-infused thermoplastic glass fibre-reinforced composites based on Elium®. Reversibility is enabled by integrated resistance heating through coated carbon veils, allowing controlled bonding, debonding and rebonding processes within a defined thermal process window between the DSC-measured glass transition temperature and the TGA-measured degradation temperature. Lap-shear testing demonstrated an initial joint strength of 11.48 ± 2.29 MPa, which dropped to near zero upon activation of the debonding-on-demand mechanism. After rebonding, joints recovered their mechanical performance reaching a lap-shear strength of 11.29 ± 3.05 MPa. Fractography reveals uniform and seamless joints, yet with border effects due heat inhomogeneity. Fracture occurs within the fusion bonding zone, supporting the reliability of the approach and allowing for debonding and rebonding without damaging the substrates. Upscaling assessment of up to 33 cm long samples reveals an increasing veil length led to linear increase in the electrical resistance as well as higher power and time requirements, which could be mitigated by multilayer heating elements with an extra layer reducing resistance by 60%. The results highlight the potential of integrated resistance heating for reversible joining of thermoplastic composites, contributing to circularity through repairability, reusability, and disassembly of composite structures.