An integrated constitutive model for tensile failure analysis and overlap design of adhesive-bonded composite joints

An integrated constitutive model is proposed for tensile failure analysis and overlap design of adhesive-bonded composite joints. In this model, two improved criteria are developed: for matrix failure and fiber failure of laminates, an improved 3D strain-based Tsai-Wu criterion is developed by introducing mode factors and an exponential progressive damage evolution; for delamination and debonding, an improved 3D coupled exponential cohesive zone model (CZM) is developed by introducing new tangential components. Both criteria are implemented in one explicit user subroutine to facilitate applications for engineering. The validity of the model is proved in comparison with the experimental results of adhesive-bonded composite single-lap joints and other numerical models. Based on the model, the influence of different overlap lengths on the tensile failure behavior of the adhesive-bonded composite single-lap joints is analyzed comprehensively. For the adhesive-bonded composite single-lap joints tested in this study, an equivalent load-weight ratio is proposed to reflect the relative load capacity, and the optimal value of the overlap length is discussed.