Analysis and design of adhesively bonded corner joints: fillet effect

Abstract In this study, stress and stiffness analyses of corner joints with single corner support, consisting of two plates, one of which was plain and the other bent at right angles, have been carried out using the finite element method. In actual adhesively bonded joints, a certain amount of adhesive, called the spew or fillet, gathers around the free ends of the adhesive-adherend interfaces. A previous study neglected the effect of the adhesive fillet on the adhesive stresses. Therefore, in order to obtain more reliable and accurate results, the effect of the adhesive fillet on the adhesive stresses and the stiffness of the corner joint has been investigated. It was assumed that the plates and adhesive had linear elastic properties. The corner joint was analysed under three loading conditions, two linear and one bending moment. For loading in the y- direction and the bending moment the peak adhesive stresses occurred at the lower free end of the vertical adhesive layer-support interface, around the support corner inside the adhesive fillet, and at the lower free end of the vertical adhesive layer-vertical plate interface for the corner joint whose adhesive layer had a square end. The adhesive fillet also resulted in considerable decreases in the peak adhesive stresses for loading in the y- direction and the bending moment. However, for loading in the x- direction it caused small increases in the adhesive stresses, with the peak stresses again around the corner of the vertical plate inside the fillet. A second corner joint with double corner support, whose horizontal plate is reinforced by a support which is an extension of the vertical plate (designed to reduce the peel stresses which are critical for the first corner joint), was investigated. Although the adhesive fillet had the same effect on the stress distribution, the second corner joint resulted in considerable decreases in the adhesive stresses, particularly the peel stresses. A third corner joint with single corner support plus an angled reinforcement member was investigated as an alternative to the previous two configurations. The adhesive fillet had the same effect on the adhesive stresses around the adhesive free ends and the adhesive stresses were low compared to those of the previous types of corner joints and those in all corner joints whose adhesive layers had square ends. In the stiffness analysis, the effects of the geometry of the corner joints, particularly the adhesive fillet, were investigated under three loading conditions. The analysis including the adhesive fillet gave corner joints with higher stiffnesses for all loading conditions. For the three types of corner joint, the results were compared with those of the previous study and recommended designs were determined based on the stress analysis and on the overall static stiffness of the corner joints.