The theory of anisotropic thin- and thick-walled closed cross-section beams with coupled elastic deformations

An efficient and accurate anisotropic closed-section beam theory has been developed for both thin- and thick-walled composite beams. In this theory transverse shear effects, both of the cross-section and of the beam walls, are taken into account. Torsional warping, both free and constrained as well as both primary and secondary, was also considered. An efficient method to account for 3-D elastic effects was developed by incorporating refined stiffness coefficients. All these effects play important roles in thin-walled composite beams and are accentuated as the wall thickness increases. The predictions of the present theory for thin-walled beam cases have been validated by comparison with available experimental data, other closed-form analysis, and refined beam finite element simulation. Good correlation between the present theory and other results was achieved for all test cases and layup sequences, regardless of beam cross-sectional configurations. Three-dimensional finite element analysis using ABAQUS has been performed for a cantilevered circular thick section beam under pure tip torque and a cantilevered thick-walled box beam under tip shear or torsional loading in an effort to validate the present theory for thick-walled beams. Again, the correlation between the predicted results from the present theory and 3-D FEA results was very good. The present theory generally predicted beam deformations for all cases within 10% of experimental data for thin-walled beams and 3-D FEA results for thick-walled cases. The present theory was applied to examine several non-classical effects such as coupled deformations, primary and secondary torsional warpings, and coupled 3-D beam stiffnesses.U of I OnlyETDs are only available to UIUC Users without author permissio