Stress Determination at Skin-Stiffener Interfaces of Composite Stiffened Panels Under Generalized Loading

Abstract

An approach is presented to calculate stresses at the skin-stiffener inter faces of composite stiffened panels. The skin and stiffener can have general anisotropic layup and the loading can be in-plane or out-of-plane as long as the in-plane stresses far from the flange edge can be at most linear in the out-of-plane direction. A stress-based en ergy minimization is used with a variational calculus derivation of the governing equa tions. All six stresses are determined at the skin-stiffener interface. Comparison of the present closed form solution with a finite element solution shows good agreement. The stresses determined with the present method are used in a failure criterion to predict onset of delamination. The effects of geometry and layup on the onset of delamination for various loadings are investigated and several trend curves useful for design applications are presented.