The bonding strength of metal-metal single-lap joints with different adhesives applied on steels and aluminum alloys were studied. The bonding strength is found to be related to the type of adhesives and the backing metal, the surface roughness, the surface scratch orientations, the adhesive layer thickness, and the loading conditions (static vs. cyclic and loading rate). SEM observation of fractured surfaces reveals some common feature of bonding strength enhancement, fracture paths and the mechanisms of fracture. The direction of the adhesive joint design is suggested.

Experimental and numerical investigation of the effect of key joint variables on the static and fatigue performance of bonded metallic single-lap joints, In this paper, numerical and experimental methods are employed to investigate the effect of surface preparation, adhesive type and thickness, and nanoparticle enrichment on the mechanical performance of bonded metallic single-lap joints. Adherents are made of similar materials; namely, steel-on-steel or aluminum-on-aluminum. Investigated surface preparation variables include roughness and scratch orientation. Adhesive-related variables include thickness, type, and nanoparticle enrichment. Four different commercially available adhesives are investigated, some of which are nanoparticle enriched for the purpose of this study. Static and/or fatigue testing as well as damage analysis-based numerical prediction of joint performance, are provided. Scanning Electron Microscope (SEM) is used for macro joint characterization through the micro observation of joint fracture surfaces. Experimental fatigue data correlates reasonably well with the numerical results obtained from damage-coupled cohesive model of the adhesive layer.