Stress analysis of thin adhesive bonding dissimilar adherends single lap joints

Abstract

In recent years, adhesives have been widely used to bond dissimilar material members particularly in aircraft and automobile structures. If the adhesive layer is very small compared with adherends, a more refined mesh model is needed for FEA modeling. That will take a lot of CPU-time to compute solution. However, there is a method to solve the adhesive lap joints by simulating the adhesive layer with spring elements called the TALA (Thin Adhesive Layer Analysis) method. The objective of this paper is to demonstate a way to analyze the stress distrubution in generalized single-lap adhesive joints of dissimilar adherends by using the FEA and TALA method. First, to validate the FEA-TALA models, the FEA-TALA results will be compared with existing results. Second, the adhesive layer of lap joints of dissimilar adherends will be studied under variation of the Young's modulus ratio between the adherends E3/E1 (0.5, 1.0, 2.0, and 3.0) and the adherend thickness ratio h3/h1 (0.5, 1.0, 1.5, and 2.0) to understand their effects on the interface stress distribution. The use of the TALA method with adhesive lap joints has been validated and shows good agreement with Sawa's solution. Futhermore, the results show that stresses increase sharply at the edge of the lap interface and that the peak normal stresses and peak shear stresses are increased when the difference in the value of Young's modulus between the upper and lower adherend is increased. The results also show that the both peak stresses at the edge of thicker adherend side is higher than another. Therefore, the best way to minimize the singular stress in adhesive layer is to keep the Young's modulus ratio and adherends ratio near to unity.