Exploring the mechanical and sensing capabilities of multi-material bonded joints with carbon nanotube-doped adhesive films

Single lap shear tests are carried out at the joints of similar and dissimilar materials, and their electrical resistance through thickness is monitored to evaluate their sensing capabilities. Al-Al and carbon fibre reinforced polymer (CFRP)-Al joints are manufactured with two types of surface treatments of the Al substrates: brushing (B) and grit blasting (GB). The lap shear strength (LSS) is higher with grit blasting due to the optimum surface roughness and the creation of an active surface. Carbon nanotube (CNT)-doped samples are detrimental to the LSS in Al-Al joints compared to the neat adhesive, while a slight increase in LSS for CFRP-Al and CFRP-CFRP is observed due to a better CNT-CFRP interaction and good load transfer between the substrates. Electrical monitoring tests are strongly influenced by the surface treatment with better adhesive-substrate interfaces leading to a more stable response and higher sensitivity, proving the high applicability of the proposed technique.