Non-linear pre-buckling behavior of shear deformable thin-walled composite beams with open cross-section

A kinematic model is presented for thin-walled composite beams able to account for axial, bending, torsion and warping strains. Shear deformations on the mid-surface are considered and modeled by means of a polynomial approximation employing suitable shape functions on the curvilinear abscissa along the cross-section mid-line. Small strains and moderate rotations are considered over the pre-buckling range. The model allows to predict the static non-linear behavior and the critical loads of composite pultruded beams. A finite element approximation is derived from a variational approach. Some numerical results are also presented revealing the importance of shear terms on the mechanical response and their effect on the stability of pultruded composite members