Fatigue and fracture behavior of adhesive-bonded structures in the light of the surface morphology

Abstract In order to obtain light weight structures, the adhesive-bonding technique has been established since many years, especially in the aircraft industry. In principle, light weight structures consist of carbon fiber-reinforced plastics (CFRP) or Al-based alloys. Under external forces, the mechanical behavior of the adhesive-bonded structure was determined by cohesive and adhesive forces. Consequently both, the cohesive as well as the adhesive strength must be as high as possible to obtain structures that resist high external forces. The mechanical behavior of the bonded structure depends sensitively on the quality of the surface prior to the curing process. In case of adhesive - bonded Aluminum-based structures, the surface can be improved by a special laser beam treatment. It can be shown that the morphology of the internal surface between the substrate and the adhesive determines the adhesive strength and, consequently, the mechanical behavior of the bonded structure. The kind and critical force of fracture (cohesive or adhesive) can be explained by using a damage model that takes the kind and distribution of characteristic defects into account.