Comparative study of CFRP single lap joints bonded with structural epoxies and a novel hot-melt film adhesive: effects of temperature and loading rate

This is the authors' abstract. We don't add key points for this paper.

Delamination remains a critical limitation in the structural application of composite materials, particularly in adhesively bonded joints. This study investigates an alternative approach to delay delamination by using a non-structural thermoplastic adhesive to form the join. The proposed method does not rely on mechanical reinforcement but rather on the intrinsic properties of the thermoplastic to absorb energy and mitigate crack propagation. Single lap joints (SLJs) were tested under two displacement rates of quasi-static (1 mm/min) and impact (3 m/s), to evaluate the strain rate sensitivity of the joints. Additionally, the performance was assessed across three environmental conditions: sub-zero (−30 ◦ C), room temperature, and elevated temperature (80 ◦ C), to study thermal effects on the adhesive’s mechanical behaviour. Results demonstrated that delamination can be completely avoided, showing that the presence of the thermoplastic layer delayed its onset and increased the energy absorption capacity of the joint, particularly under impact and low-temperature conditions. The findings suggest that non-structural thermoplastics may offer a lightweight and effective delamination mitigation strategy for composite joints operating in variable service environments.