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

Concerning higher-order shear deformation theories (HSDT) for composit e plates, this article presents a numerical investigation on local cha racteristics (distribution along the plate thickness of in-plane displ acement, in-plane normal stress, and transverse shear stress component s) in the large deflection and postbuckling fields. The von Karman the ory irt conjunction with a recent mixed two-dimensional model; elsewhe re denoted by the acronym RMZC (Reissner-Mindlin zigzag continuity) is employed The RMZC model assumes two independent fields along the plat e thickness for displacements and transverse shear stresses, respectiv ely; the displacement model describes the so-called zigzag form for th e in-plane components, while the stress field fulfils interlaminar equ ilibria. Standard displacement formulation is enforced by employing va riationally consistent constitutive equations between stress and displ acement unknowns. Finite-element-type approximations are introduced on the plate domain, leading to governing equations in the form of a non linear system of algebraic equations. This is solved through applicati on of the Newton-Raphson method accounting for arc length strategies. Explicit forms of the linear and nonlinear resulting matrices are quot ed in appendixes. The numerical investigation and discussion concern l arge-deflection and postbuckling analysis of symmetrically laminate sq uare thick/thin plates subjected to simply supported and clamped bound ary conditions. Results of the RMZC model are compared with lose relat ed to CLT classical lamination theory (CLT) and first shear deformatio n 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 huge deflections as well as postbuckled equilibr ium states of thick plates are considered while for the thin-plate ana lyses, FSDT and RMZC have furnished very close results.