Finite Element Analysis of Geometrically Nonlinear Thin-Walled Composite Laminated Beams

The purpose of the present work is to develop a finite element model for structural analysis of composite laminated thin-walled beam structures, with geometrically nonlinear behavior, including torsional warping deformation. The structural deformation is described by an Updated Lagrangean formulation. To define the load-deflection path, a generalized displacement control method has been implemented. We have considered a thin-walled section made from an assembly of flat layered laminated composite elements. The parts like a flange and a web in a section will be referred to as a panel. The cross-section bending-torsion properties are integrals based on the cross-section geometry, on the warping function and on the individual stiffness of the laminates that constitute the crosssection. The cross-section geometry is discretized by quadratic isoparametric finite elements in order to determine its bending-torsion properties. The structural discretization is formulated throughout three-dimensional two-node Hermitean finite beam elements, with seven degrees of freedom per node. In numerical examples a thin-walled cross-section cantilever beam is considered. The influence of the lamina orientation on the critical load is studied.