Stress Distribution in Adhesive Joints with Tapered Laminates — Effect of Tapering Length and Material Properties

Abstract

One major problem when using bonded fiber-reinforced plastic laminates to strengthen and upgrade existing structures is the high stresses in the adhesive layer, in the area close to the end of the laminate, which might govern the failure of the joint. One method that has been put forward as a means of reducing the stress concentration in this area, is to taper the end of the laminate. Although this method has been suggested by some design guidelines, no specific information is usually provided about the tapering type, required tapering length, and limitations associated with this method. A parametric study has been carried out to investigate the effect of tapering length and the material properties of joint constituents, i.e., stiffness of the laminate and adhesive, on stress distribution in adhesive joints using the finite element method. Two different configurations, including normal and reverse tapering, were considered. The results indicated that the effect of tapering on stress distribution is highly dependent on the stiffness of the laminate and the adhesive used in the joint. It was concluded that tapering is more effective in joints with softer laminates and stiffer adhesives. Reverse tapering was found to have more favorable effects on stress reduction in comparison to normal tapering.