Generalized Multifield Variational Sectional Analysis of Composite Blades Considering Nonuniform Torsion

A finite element (FE) cross-sectional analysis is developed based on the Reissner's multifield variational principle to model the three-dimensional (3D) warping displacements and sectional stresses. The classical elastic couplings are taken into account along with the rigorous treatment of nonclassical couplings due to nonuniform torsional warping. The in- and out-of-plane warping displacements, and sectional stresses are approximated as linear functions of generalized sectional stress resultants at the global level, and using FE shape functions at the local sectional level. A generalized Timoshenko-Vlasov level 7 x 7 stiffness matrix is formulated which incorporates Timoshenko like model for bending, and Vlasov like model for restrained torsion. The accuracy of the present analysis is substantiated using a variety of benchmark composite beams and rotor blades. The present results show a good correlation compared with other state-of-the-art methods, 3D FE analysis and/or experimental data.