Flexural–Torsional Couplings in Thin-Walled Beam Sections Having Variable Stiffness

This work tries to study the flexural–torsional couplings in thin-walled composite beams having variable stiffness. Variable stiffness composites (VSC) are manufactured with curvilinear fibres. Compared with straight fibre laminates, variable angle tow sections have improved structural response as they redistribute the in-plane stresses. A generalized beam kinematic model which considers the effect of flexural, torsional and warping deformations is adopted and using the principle of minimum potential energy, governing set of equations are derived. The variable fibre angles are defined using a general Lagrangian polynomial and as a special case, linearly varied fibre angles are studied. The transverse shear deformation effects are neglected in the present model and through set of C1 continuity finite elements, governing equations are numerically solved. The results are validated for the constant fibre angle composites and further, important observations are drawn on the coupled response of thin-walled VSCs. The present kinematic model and the numerical scheme is capable of extending the problem to further study the vibration and stability response of these composites.