Stresses in double-lap joints bonded with a viscoelastic adhesive. II - Parametric study and joint design

Abstract

A parametric study of the behavior of double-lap joints, bonded with a viscoelastic adhesive, is presented in this paper. The study is based on Schapery's Direct Method of viscoelastic stress analysis in the SAAS III finite element program as described in Part I of this paper. In this study, the relative importance of the various material and geometric parameters is quantitatively determined in order to design an efficient joint. The most important parameter is the ratio of the adherend modulus to the equivalent property of the viscoelastic adhesive. The stresses are highest when this ratio is one and decrease as this ratio increases. The next most important parameter is the thickness of the adhesive. With decreasing adhesive thickness, the stress distribution along the length of overlap is increasingly uniform and the gradient of the stress distribution through the adhesive thickness also decreases. The length of overlap influences only the location of the maximum shear stress, whereas a change in the relative thicknesses of the adherends has a minimum influence on the magnitudes of the stresses. The results are all presented in nondimensionalized units so that the criteria for an efficient joint are clearly delineated.