ZIGZAG AND INTERLAMINAR EQUILIBRIA EFFECTS IN LARGE-DEFLECTION AND POSTBUCKLING ANALYSIS OF MULTILAYERED PLATES

Concerning, higher-order shear deformation theories (HSDT) for composite plates, this article presents a numerical investigation on local characteristics (distribution along the plate thickness of in-plane displacement, in-plane normal stress, and transverse shear stress component;) in the large-deflection and postbuckling fields. The von Kdrmdn theory in conjunction with a recent mixed two-dimensional model, elsewhere denoted by the acronym RMZC (Reissner-Mindlin zigzag continuity) is employed. The RAfZC model assumes two independent fields along the plate thickness for displacements and transverse shear stresses, respectively; the displacement model describes the so-called zigzag form for the in-plane components, while the stress field fulfils interlaminar equilibria. Standard displacement formulation is enforced by employing variationalty consistent constitutive equations between stress and displacement unknowns. Finite-element-type approximations are introduced on the plate domain, leading to governing equations in the form of a nonlinear system of algebraic equations. This is solved through application of the Newton-Raphson method accounting for arc-length strategies. Explicit forms of the linear and nonlinear resulting matrices are quoted in appendixes. The numerical investigation and discussion concern large-deflection and postbuckling analysis of symmetrically laminate square thick/thin plates subjected to simply supported and clamped boundary conditions. Results of the RMZC model are compared with those related to CLT classical lamination theory (CLT) and first shear deformation theory (FSDT). It has been confirmed that the importance of effects related to the RMZC model are more evident when local characteristics are described. Furthermore, it has been found that such effects become more significant when large deflections as well as postbuckled equilibrium states of thick plates are considered, while for the thin-plate analyses, FSDT and RMZC have furnished very close results.