A new mixed model based on the enhanced-Refined Zigzag Theory for the analysis of thick multilayered composite plates

In this paper, a new mixed model based on the enhanced Refined Zigzag Theory for thick multilayered composite plates is formulated. The kinematics is assumed cubic for the in-plane displacements and parabolic for the transverse one. The set of kinematic variables is reduced by using a partial constraint on the transverse shear stress, and a new set of enhanced cubic zigzag functions are obtained. The transverse normal stress is assumed as a smeared cubic function along the laminate thickness. The assumed transverse shear stresses profile is derived from the integration of local three-dimensional equilibrium equations involving a new set of strain variables. The entire formulation is developed by involving the Hellinger-Reissner functional and a penalty term for the strains compatibility; the governing equations and the consistent boundary conditions are derived. Finally, to assess the proposed model's predictive capabilities for general multilayered laminated and sandwich plates, results are compared with exact three-dimensional solutions available in the literature.