Boundary-Layer Effects in Composite Laminates: Part 2—Free-Edge Stress Solutions and Basic Characteristics

Abstract

Boundary-layer effects in composite laminates are considered. Based on the theory of anisotropic elasticity and Lekhnitskii’s complex-variable stress function formulation, the exact laminate elasticity solution is derived for the problem. The solution contains the exact boundary-layer stress singularity and higher-order terms in eigenfunction series. Convergence and accuracy of the solution are studied, and present results are compared with existing approximate numerical solutions. For illustrative purposes, the complete solution for a symmetric [45/−45 / −45/45] graphite-epoxy composite is presented to elucidate fundamental characteristics of the boundary-layer effects. Detailed stress distributions in the boundary-layer region are determined. Boundary-layer stress intensity factors are introduced to characterize the singular edge-stress field. Physical significance of the parameters is discussed in the realm of fracture initiation and failure modes in the laminate boundary region.