Laminated composite open profile sections: non-uniform torsion of I-sections

A general theory proposed earlier (Muddur SS, Chaturvedi SK. Composite Structures 1999;45:105¯14) is simplified to analyse the deformation response of I-sections made of laminated fiber-reinforced composite materials. The resulting field equations are further simplified and solved to determine the rotational and warping deformations of I-beams subjected to only non-uniform torsional loads. The numerical results for a cross-ply laminated graphite¯epoxy cantilever I-beam subjected to a torsional load at the free-end show good correlations with the available experimental and theoretical results. The restraining of warping deformation amounts to a significant increase in the torsional stiffness of the beam. Some additional results for cross-ply glass¯epoxy and steel beams are also consistently good.