Influence of surface morphology on the adhesion strength of epoxy–aluminum interfaces

Adhesively bonded aluminum joints have been increasingly used in automotive industry because of their structural and functional advantages. Interfacial debonding in these joints has become a major concern limiting their performance. The present work is focused on experimental investigation of the influence of surface morphology on the interfacial fracture behavior of aluminum/epoxy interface. The specimens used in this experimental study were made of an aluminum/epoxy bimaterial stripe in the form of a layered double cantilever beam (LDCB). The LDCB specimens were debonded by peeling off the epoxy layer from the aluminum substrate using a steel wedge. Interfacial fracture energy was extracted from the debonding length by using a solution for the specimen geometry based on a model of a beam on an elastic foundation. This model was validated by direct finite element analysis. The experimental observations establish a direct correlation between the surface roughness of aluminum substrate and the fracture resistance of the aluminum/epoxy interface. The results emphasize the importance of choosing surface features at an appropriate length scale in studying their effects on interfacial fracture resistance.