Condition monitoring of defective single lap adhesive joint using carbon nanotubes

Adhesive joints have been employing in engineering structures such as marine, aerospace, automotive, oil and gas industry. Since the joints are the weakest part of engineering structures, the fracture possibility in adhesive joint is high. Therefore, structural health monitoring of adhesive joint is an important issue. The aim of this paper was condition monitoring of damage in the single lap adhesive joint by multiwall carbon nanotubes. This work is carried out by recording the electrical resistance change during the mechanical loading. This damage propagation is observed as a crack extension in adhesive joint. Firstly, MWCNTs with 9 wt.% are dispersed in an epoxy resin by ultrasonic device. Then, the hardener is added to the nonoadhesive. The obtained material is immediately poured into single lap adhesive joint mold. The defective adhesive joints were manufactured with circular and square defects in different sizes i.e. 10%, 30% and 70% overlap area. The specimen is subjected to tensile test and electrical resistance change are recorded during the shear load. The results showed that the maximum value of relative resistance change is occurring in the adhesive joint comprises of square defect with 30% overlap area of defect. In this situation, the crack was propagated in nanoadhesive and a small part of a crack was extended from defect boundary.