Healing potential of reversible adhesives in bonded joints

Impact loads transferred to the bondline of adhesive joints can result in deterioration of the bond and significantly decrease the load carrying capacity. If the damage in the adhesive layer can be healed or reversed, such losses in structural behavior can be recovered. One such healing technique can be implemented in the use of thermoplastic ‘reversible adhesives (RA).’ RA are thermoplastics doped with conductive nanoparticles that can be rapidly heated/melted through exposure to electromagnetic radiations and can be used to heal/repair bonded joints. In this work, single lap joints (SLJ) were bonded using ABS (Acrylonitrile butadiene styrene) thermoplastic reinforced with ferromagnetic nanoparticles (FMNP). The joints were subjected to impact loads (10 J) to induce bondline damage followed by lap-shear tests to obtain damage-induced performance. Next, the impacted joints were subjected to electromagnetic (EM) exposure to introduce healing followed by lap-shear tests to obtain the healed performance. Results were compared with pristine, non-damaged lap-joints. To obtain the efficiency of EM-based healing, a parallel study was carried out to heal the impacted samples by heating in a convection oven. The loss in joint strength due to impact and its subsequent recovery due to healing was evaluated. Up to 92% of joint strength was regained through both oven and EM based healing whereas the processing time for EM based healing was 60 times faster than oven-based healing.