Monitoring the crack length of adhesively bonded carbon-fiber-reinforced polymer by using aligned graphene

In this study, the lengths of cracks in composite joints bonded with epoxy were monitored by evaluating the electrical resistance. Samples of double cantilever beam joints bonded with epoxy-containing aligned graphene were subjected to Mode I fracture tests. During sample fabrication, 0.15 wt% graphene was included in the epoxy and then aligned under an electrical field. The presence of aligned graphene resulted in the formation of an electrically conductive medium between composite adherents. During the fracture tests, the variation in resistance with the crack length was recorded; the resistance of the adhesively bonded joint increased with the crack length. The experimental results for the relationship between the resistance and crack length agree well with theoretical predictions. The functionalized epoxy exhibited homogeneous electrical conductivity, which indicated that the aligned graphene was uniformly dispersed in the epoxy. Thus, epoxy functionalized with aligned graphene can be used to detect the lengths of cracks within composite joints.