Evaluation Method of Adhesive Fracture Toughness Based on Double Cantilever Beam (DCB) Tests Including Residual Thermal Stresses

Abstract

The energy release rate associated with crack growth in adhesive double cantilever beam (DCB) specimens, including the effect of residual stresses, was formulated using a beam theory. Because of the rotation of the unsymmetric arms in the adhesive DCB specimens due to temperature change, it is necessary to modify the evaluated fracture toughness of DCB specimens, particularly in the case of the large temperature change. In this study, it was shown that the difference between the apparent toughness and the true toughness due to the residual stresses can be calculated for the given specimen geometry and the thermo-mechanical properties, such as the coefficient of thermal expansion. The calculated difference of the energy release rates based on the present modification method is compared with that from FEM to verify the method. The residual stress effects on the evaluation of the adhesive fracture toughness are discussed.