The effect of adhesive bonding between aluminum and composite prepreg on the mechanical properties of carbon-fiber-reinforced metal laminates

Abstract

The role of adhesion between aluminum sheets and fiber composite prepreg on the mechanical property profiles of carbon-fiber-reinforced metal laminates (CFRMLs) has been investigated. Differences in adhesive bonding were achieved by using two different aluminum surface treatments, one with a standard P2-Etch procedure and another with a modified FPL-Etch procedure with the subsequent application of a silane coupling agent. Double-cantilever beam (DCB) tests were conducted to measure the interfacial fracture energy, and an increase in interfacial fracture toughness by up to six times was achieved by using the latter method. Optical and scanning electron microscopy were used to study the failure behavior and fracture mechanisms of the CFRMLs. No clear differences were found in laminate mechanical properties such as tensile strength and Young's modulus. A reduction of 10% in the relative value for the interlaminar shear strength (ILSS) was observed for the laminate with poor interfacial adhesion associated with the P2-Etch method, in both three- and five-point bend tests. However, the residual strength of the notched CFRMLs is, in general, almost independent of the adhesion status between aluminum sheets and composite prepreg, although a slight increase in residual strength for laminates with weak interfacial adhesion was observed in the presence of small holes, because of the difference in delamination growth.