In this study, a new method of bonding CFRP and Al6061-T6 with epoxy adhesive after shot-peening treatment on the surface of Al6061-T6 specimens was proposed to improve bonding strength of a single lap joint between CFRP and Al6061-T6. More specifically, correlation between shot peening coverage on the Al6061-T6 surface and bonding strength with CFRP was experimentally analyzed. Experimental results showed that the surface roughness and the bonding strength increased as the peening time on the surface of Al6061-T6 increased up to a specific peening time (or coverage). However, the surface roughness and bonding strength decreased again under an over-peening condition of 480 seconds (300% coverage) or more. Therefore, it is necessary to search for the optimal peening time that can maximize bonding strength as well as the fatigue life of parts at a peening time between 320 (200%) and 480 s (300%) through additional experiments in future studies.

Shot peening is widely used to improve the fatigue life and strength of various mechanical parts and an accurate method is important for the prediction of the compressive residual stress caused by this process. A finite element (FE) model with an elliptical multi-shot is suggested for random-angled impacts. Solutions for compressive residual stress using this model and a normal random vertical-impact one with a spherical multi-shot are obtained and compared. The elliptical multi-shot experimental solution is closer to an X-ray diffraction (XRD) than the spherical one. The FE model’s peening coverage also almost reaches the experimental one. The effectiveness of the model based on an elliptical shot ball is confirmed by these results and it can be used instead of previous FE models to evaluate the compressive residual stress produced on the surface of metal by shot peening in various industries.