Evaluation of the fatigue strength of adhesively bonded CFRP/metal single and single-step double-lap joints

Generally, the adhesive layer of an adhesively bonded joint is under a state of concentrated multiaxial stress. Hence, stress multiaxiality and concentrated stress distributions must be taken into account in estimating the strength of adhesive joints. In our previous study. [1], a fatigue-failure criterion was investigated which took account of the stress multiaxiality in adhesively bonded CFRP/aluminum butt, scarf and thick-adherend lap-shear joints, which have uniform stress distributions in the adhesive layer. Another parameter governing the strength characteristics of the adhesive joints is the concentrated stress distribution due to the stress singularity at the corners of the adhesive/adherend interface, Recently, stress-singularity parameters have been used to evaluate the strength of adhesive joints. However, there are few studies evaluating the fatigue strength from this point of view. In this study, a method of estimating the fatigue strengths of adhesively bonded single-lap, tracked single-lap and single-step double-lap joints composed of CFRP and an aluminum alloy is proposed which is based on two stress-singularity parameters. (C) 1999 Elsevier Science Ltd. All rights reserved.