Extension-Twist Coupling of Two-Layered Angle-Ply Laminates

Abstract

Two-layered angle-ply laminates twist under a tensile load. In the present paper the phenomena are analyzed first by a classical lamination theory. The results of the numerical calculations show that the twist angles of the laminates highly depend on the fiber directions and that the direction of twisting is either positive or negative depending on the material properties and the fiber directions. The phenomena are next analyzed by extending the theory of torsion of bars. The analysis is carried out by the utilization of the Hellinger-Reissner principle and the Ritz method. In the analysis the untwist effects which are observed in pre twisted isotropic rods under a tensile load are also taken into account, but the effects are found to be small.