A zigzag quasi-3D theory for bending analysis of general laminated composite and sandwich plates

This study presents an enhanced Zigzag Quasi-3D theory for the static bending analysis of laminated composite and sandwich plates under transverse loading. Unlike existing Quasi-3D and conventional zigzag theories, the proposed formulation simultaneously accounts for transverse shear deformation, transverse normal stretching, and layerwise zigzag behavior within a unified equivalent single-layer framework while maintaining a fixed number of generalized variables independent of the number of layers. Layerwise zigzag functions are incorporated into the displacement field to capture in-plane slope discontinuities at lamina interfaces, while the kinematic model follows the Carrera and Koiter recommendations for thickness stretching. The primary objective is to develop an accurate and computationally efficient formulation for laminated and sandwich plates with arbitrary stacking sequences. Governing equations are derived using the principle of virtual work, and closed-form solutions are obtained through Navier’s method for simply supported plates. The formulation is validated for cross-ply, angle-ply, and sandwich plates. Transverse shear stresses are recovered through equilibrium-based integration to obtain continuous through-thickness distributions. Comparisons with benchmark three-dimensional elasticity solutions demonstrate accurate prediction of global and local responses, realistic zigzag behavior, and significantly improved displacement and stress predictions while retaining high computational efficiency.