Torsion of Thin Orthotropic Open Sections

Abstract

Torsion of thin rectangular laminated rods is considered. Although thin open sections are inefficient in torsion, a predictive capability for stiffness and strength is often required in design. An existing theory for torsion of laminated cross-sections is reviewed, and the effects of warping restraint are developed for thin sections. Experiments are reported for torsion of IM6/3501-6 carbon/epoxy laminated specimens with both thin rectangular and angle shapes. The experiments correlate well with the theory for stiffness and strain, and demonstrate the effects of lamination sequence and the equivalence of the rectangular and angle shapes. Pronounced nonlinear response is seen for certain layups. Failure is generally in accord with predictions based on interlaminar shear stress.