Boundary-Layer Hygroscopic Stresses in Angle-Ply Composite Laminates

Abstract

An investigation on hygroscopically- induced stress fields near g eometric b oundaries of finitewidth, a ngle-ply composite laminates is presented. The study is formulated on the b asis of the t heory of anisotropic hygroelasticity. By the i ntroduction of Lehknitskii's complex stress functions, governing partial differential equations of the sixth-order are established for composite laminates subjected to uniformly distributed moisture absorption. The hygroscopic stress singularity at the edges of a c omposite laminate is determined b y an eigenfunction expansion technique recently developed by the authors. Distributions of stresses and associated strain energy densities in the boundarylayer region of the composite laminate are obtained by using a boundary-colloca tion method. A symmetric, angle-ply (45°/-450/-450/4 50) graphitel epoxy is chosen for illustrative purposes in this study. The solution for the (+45), composite is presented to elucidate t he fundamental behavior of hygroscopic edge stresses in composite laminates. Of particular i nterest are the p resently introduced hygroscopic b oundary-layer stress intensity factors and their implications. Details of these are reported in the paper.