A closed-form solution for stresses at curved free edges in composite laminates: A variational approach

An analytical method developed for determining the interlaminar stresses at straight free boundaries is extended to predict the free-edge stresses at curved boundaries of symmetric composite laminates under in-plane loading. The three-dimensional (3D) stress distribution in laminates with curved boundaries is approximately described on the basis of a zero-order approximation of the boundary-layer theory. The related stress functions are found by minimization of complementary energy and the variational principle, and satisfy zero-order equilibrium equations, boundary conditions and traction continuity at interfaces between plies. Results obtained from the present method are compared with those in the literature for laminates with both straight edges and circular holes. This method provides a computational technique with the advantage of simplicity and versatility for analyzing the 3D stresses in composite laminates of general ply orientations with curved boundaries.