Strength model of adhesive bonded double lap joints under cantilevered bending

Abstract

The objective of this study was to develop mathematical relations for predicting the strength of adhesive?bonded double?lap joints under cantilevered bending. Based on the strength of composite materials theory, two models were proposed to predict the stress?strain distribution and vertical deflection of the laminates and the adhesive under this loading condition. The first model was based on the basic beam theory with the assumption that every cross section in a plane before bending remains plane after the bending load is applied. In the other model, a strain gap between each bonded surface is assumed. Based on the second model and the predicted peel failure mode, the effects of shear modulus of the adhesive, joint length, and adhesive thickness on the joint strength were evaluated. Scotchply composite laminates were used as the adherends of the double?lap joints in the experimental investigation. An Instron machine fitted with a special apparatus was used for conducting the experiments. By the attachment of strain gages to the adherends and through the use of a dial indicator, the theoretical models were verified experimentally.