Tuning the properties of functional adhesives with hybrid nanofillers for structural health monitoring

Monitoring the damage of adhesive joining could avoid potential accidents in multimaterial lightweight vehicles. Different from the additional sensors, a kind of functional adhesives with hybrid fillers of carbon nanotubes (CNTs) and carbon black (CB) was developed, and verified by in-situ sensing of adhesion damage in single-lap shear joints (SLAJ) of composite-to-metal. The influences of the total weight percent of fillers and relative ratio of CNT-to-CB on the mechanical, piezoresistive and the microwave absorption performance of SLAJ were investigated experimentally. The addition of both CNTs and CB increases the cohesive shear strength but decreases the failure strain at the same time. For the formula of total 2wt.% fillers and CNT:CB = 1:3, the shear strength of SLAJ is nearly 37.50% higher than that of pure adhesives. Both CNT and CB lead to the reduction of electrical resistivity. When approaching the failure strain, the electric resistances for all CNT-to-CB ratios increase sharply. For this formula, the relative electric resistance ratio is 29% at strain 0.038, close to the failure strain. The adhesives with this formula also show a better microwave absorption. This research shows a potential application of adhesives with hybrid nanoparticles in lightweight and low-cost structural health monitoring.