Adhesion Fatigue Properties of Cohesive Fracture-dominant Adhesive with Graphene Nanoplatelets

Abstract

Structural adhesives that fail in cohesive fracture mode under fatigue loading are required from the viewpoint of long-term reliability. In this paper, fatigue properties of the epoxy adhesives achieving the cohesive fracture mode were investigated. Diglycidyl ether of bisphenol A was used as the epoxy resin, and graphene nanoplatelets were selected as the functional fillers which introduced cracks into the adhesive resin layer under fatigue loading. The graphene nanoplatelets were well dispersed in the epoxy resin using a twinscrew extruder. Fatigue tests were carried out using lap shear joint specimens. The epoxy adhesive joints without the graphene failed in the interfacial fracture mode along the aluminum substrate. Whereas the almost all adhesive joints with the graphene even at the graphene concentration of 0.1wt％ failed in cohesively in the adhesive resin layer. However, the number of cycles to failure in the fatigue tests decreased as the graphene concentration increased. The epoxy matrix was toughened by core-shell rubber particles in order to improve the fatigue resistance. The adhesive with 0.1wt ％ graphene nanoplatelets and 5wt ％ core-shell rubber particles achieved the five-folded fatigue cycles to failure of unmodified adhesive while maintaining a high cohesive failure ratio. It was found that increased fracture energy of the epoxy matrix between the dispersed graphene nanoplatelets was the key for the fatigue long life.