Shear deformable composite plates with nonlinear curvatures: modeling and nonlinear vibrations of symmetric laminates

Moving from a general plate theory, a modified general shear deformable laminated plate theory (MGFSDT) exhibiting nonlinear curvatures but still allowing for some worth features of linear curvature models (von Karman) is formulated. Starting from MGFSDT partial differential equations, a minimal discretized model (Duffing equation) for symmetric cross-ply laminates nonlinear vibrations, whose coefficients account for shear deformability and nonlinear curvatures, is obtained via the Galerkin procedure. The variable features of such a Duffing model as obtainable via alternative kinematic assumptions at the continuum level are highlighted. Through the comparison of a number of underlying models in different technical situations, information on the influence of shear deformability on system nonlinear response and on the influence of nonlinear curvatures are obtained. Frequency-response curves through a multiple scale analysis are presented for different continuous models, kinds of material, mode numbers and boundary conditions.