Torsional Buckling Analysis of Composite Cylinders

A buckling analysis of composite cylinders under torsion is performed by using the geometrically nonlinear e nite element analysis. A nine-node assumed strain shell-element model with six degrees of freedom per node is used for the analysis. The buckling load of a composite cylinder is found by searching for a bifurcation point on the geometrically nonlinear deformation path. The corresponding buckling mode is obtained from the eigenvalue analysis at the bifurcation point. Numerical results show good agreement with linear solutions for isotropic and most composite cylinders, but large discrepancies in some cases. This discussion focuses on the pinpoint of the bifurcation point on the nonlinear path and the differences of torsional buckling loads between the nonlinear and linear solutions for various types of composite cylinders.