Crack Initiation Process of DCB Specimens Based on First-order Shear Deformation Theory

The current work develops an analytical model which can consider the crack initiation process of double cantilever beam (DCB) specimens. The current model is based on the first-order shear deformation beam theory, and thus includes the effect of shear deformation in the beams on the crack initiation process. The relationship between the remote peel load P and loadline deflection u is explicitly established based on a parametric equation of crack tip separation delta for the crack initiation process. The nonlinear response in the ascending branch of the loading process is captured by the present analytical model. With properly defined cohesive laws (such as exponential type), it might not be necessary to define a clear final separation delta(f) for the crack propagation. The comprehensive comparisons with test and numerical results validate the accuracy of the present model for predicting the crack initiation and propagation of DCB specimens. This model can be used for predicting the debonding process of adhesively bonded composite joints.