Plasma treatment on both adhesive tape and adherends for significantly enhanced CFRTP-related adhesive joints
Unlike existing literature that primarily concentrates on either the plasma treatment of adherends alone or solely on adhesive surfaces, this work leverages plasma modification of both adhesive in tape form and adherend surfaces to largely enhance the interfacial bonding between a thermoset-based adhesive tape and carbon-fiber-reinforced thermoplastic polymer (CFRTP) for structural bonding applications. Here, by conducting single lap shear tests on adhesively-bonded AA6061-CFRPPA (carbon-fiber-reinforced polyphthalamide) dissimilar joints, it is shown that the plasma treatment of adherends alone can increase the lap shear strength (LSS) of the joints by approximately 200% compared to non-treated counterparts. An additional plasma treatment of adhesive tape surfaces leads to even higher LSS improvement, reaching up to 315%, due to the formation of a denser crosslinked network of covalent bonds and a reduced area fraction of interfacial voids at the CFRPPA/adhesive interface. The highest plasma-enhanced LSS of the metal-CFRTP dissimilar joints rivals that of metal-metal joints, which is typically stronger than the joints associated with fiber-reinforced polymers. This study is important for achieving strong CFRTP-related structural components bonded using adhesive tape, providing better compatibility with plasma treatment and other joining methods like riveting compared to adhesive paste or liquid.