Bond Thickness Effects Upon Stresses in Single Lap Adhesive Joints

Results of an analytical investigation on the influence of bond thickness upon the stress distribution in single lap adhesive joints are presented. The present work extends the basic approach for bonded joints, originally introduced by Goland and Reissner, through use of a more complete shear-strain/displacement equation for the adhesive layer. This refinement was not found to be included in any of the numerous analytical investigations reviewed.

As a result of the approach employed, the present work uncovers several interesting phenomena without adding any significant complication to the analysis. Besides modifying some coefficients in the shear stress equations, completely new terms in the differential equation and boundary conditions for bond peel stress are obtained. In addition, a variation of shear stress through the bond thickness - no matter how thin it may be - is analytically predicted only by the present theory. This through-the-bond-thickness variation of shear stress identifies two antisymmetrical adherend-bond interface points at which the shear stresses are highest. The growth of joint failures originating from these points agrees with results obtained from actual experiments.