Effect of Laser Patterning Preprocessing on Fatigue Strength of Adhesive Bonded Joints Using Thin Steel Plate

Reducing the weight of automobile bodies would help counteract environmental problems caused by greenhouse gas emissions by improving fuel efficiency. Multi-material structures have been investigated to construct an automobile body structure composed of steel in combination with lightweight metal materials and carbon-fiber-reinforced plastic. Thus, it is necessary to develop high-quality bonding techniques that can join dissimilar materials as quickly as possible. To this end, adhesive bonding has attracted attention from the viewpoint of building multi-material structures. However, from the viewpoint of durability and reliability, it is regarded as a complementary technique used to support other industrial welding methods. Moreover, to further improve the strength of adhesive bonding, the surface conditions of the adherend must be considered. In this study, to improve the interfacial strength of adhesively bonded joints, laser patterning pre-processing was applied as a surface treatment. The fatigue properties of adhesively bonded joints were evaluated and compared with those of untreated joints. It was found that the static and fatigue strengths of the joints were improved by the laser patterning pre-processing. In particular, the joint strength was improved by removing the weak boundary layer from the entire adhesion surface with laser irradiation. Therefore, the laser patterning preprocessing method proposed in this study is a very promising process for achieving adhesively bonded joints with excellent fatigue properties.