Effects of joint geometry and material on stress distribution, strength and failure of bonded composite joints: an overview

Abstract

ABSTRACT A comprehensive literature review on the existing analytical models based on different material and geometry behaviors for both single and double-lap joints (as well as others) has been made to assist a designer to select the proper model for a particular application. The effects of environmental conditions on the joint performance are also included. The survey shows that the analytic models selected for the adhesively bonded lap joints (single or double), as well as other types of joints (i.e. butt, scarf, and stepped), with linear material properties are mostly two dimensional where the solutions for stress distribution and/or failure of the joint are investigated either analytically or by finite element method. The results seem to be generally accurate and adequate, since in most joints under unidirectional loading, stresses in the width direction are significantly lower than those in the loading direction. Although the inclusion of material non-linearity in such joints, as well as T and hybrid joints, renders the solution too complex, yet, there are many models which have included the non-linear behavior of the adhesive layer into their formulation to predict stress distribution, as well as strength and/or failure of the composite joint. This includes the viscoelastic behavior of the adhesive as well as its creep behavior. In addition, a summary of the main analyses is presented to show the applicability of different solution methods in both complex and semi-complex problems, dealing with either a simple or a composite joint with laminated adherend layers. Results show that cohesive zone models (CZM) appear to be a powerful tool for failure analysis of such joints. Moreover, a comprehensive study of various models based on either linear or non-linear material behavior of the adherend and/or adhesive (including its viscoelastic behavior) is performed on tubular joints to show the effect of material behavior on the joint failure.