Modifications to beam theory for bending and twisting of open-section composite beams

Abstract

Modifications to beam theory are presented to describe the combined bending and twisting of anisotropic composite material open-section beams subjected to pure bending and transverse loading. The beams are constructed of thin panels of laminated fiber reinforced composite materials which have either anisotropic or orthotropic in-plane mechanical properties. Due to the anisotropic coupling between normal and shear effects, three modes of beam deformation under transverse loading are obtained; bending (deflection), twisting (rotation), and axial extension or contraction (displacement). The theory is formulated in terms of effective laminate properties and describes overall beam deformation. Numerical examples are presented in which the theory is applied to describe the behavior of typical open cross-sections under a variety of loadings.