Parametric Study of Combined Adhesive-Riveted Lap Joints

Abstract

Riveted lap joints are widely used to assemble complex structures, e.g. aircraft fuselages. A thin layer of adhesive (sealant), is normally applied to lap joints in order to restrict the entry of moisture and retard corrosion. In this work, combined adhesive-riveted lap joints were studied to understand the effect of three parameters: panel thickness, adhesive stiffness and adhesive layer thickness, on single row non-countersunk riveted lap joints. Finite element analysis (FEA), along with Thin Adhesive Layer Analysis (TALA-developed for simulating the adhesive layer in lap joint models), were used to analyze the joint behavior. In previous studies, the stress concentration factor for single row riveted lap joints was found to be approximately 6.1, and the stress concentration factor for sealed riveted lap joints was approximately 5.2 for a 180 micron thick sealant layer. In this study, panel thickness, adhesive stiffness and adhesive layer thickness were varied parametrically in FEA analyses to determine their affects on the joints. The FEA/TALA results were used to predict the fatigue life of the joints as functions of the three parameters. The results show that the maximum tensile stress is smaller with a smaller panel thickness. The results also showed that the stress concentration factor in the joints was reduced when the stiffness of the adhesive layer was increased or when the thickness of the adhesive layer was decreased. Finally, fatigue tests showed that the fatigue life of the combined adhesive-riveted lap joints was greater than for riveted lap joints without adhesive.