A CLOSED-FORM SOLUTION FOR STRESSES AT CURVED FREE EDGES IN COMPOSITELAMINATES - A VARIATIONAL APPROACH

An analytical method developed for determining the interlaminar stress es at straight free boundaries is extended to predict the free-edge st resses at curved boundaries of symmetric composite laminates under inp lane loading. The three-dimensional (3D) stress distribution in lamina tes with curved boundaries is approximately described on the basis of a zero-order approximation of the boundary-layer theory. The related s tress functions are found by minimization of complementary energy and the variational principle, and satisfy zero-order equilibrium equation s boundary conditions and traction continuity at interfaces between pl ies. 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 advanta ge of simplicity and versatility for analyzing the 3D stresses in comp osite laminates of general ply orientations with curved boundaries. (C ) 1997 Elsevier Science Limited.