Abstract
A new nonlinear formulation is developed for the governing equations for shear and peel stresses in adhesively bonded composite double-lap joints. The new formulation allows arbitrary nonlinear stress-strain characteristics in both shear and peel behavior. The equations are numerically integrated using a shooting technique and the Newton-Raphson method with an in-house-developed user-friendly interface. Numerical examples are presented to demonstrate the effect of the nonlinear adhesive behavior on the stress distributions. Failure loads are predicted using an interlaminar delamination failure criterion for three groups of adhesively bonded composite double-lap joints. It is shown that the failure loads predicted using the present nonlinear adhesive model correlate well with the measured failure loads, while the failure loads computed using the linear adhesive model are only about half of the measured failure loads.