Free vibration analysis of angle-ply laminated and sandwich plates using enhanced Refined Zigzag Theory

The paper presents a numerical assessment of the free vibration of angle-ply laminated and sandwich plates using the enhanced Refined Zigzag Theory (en-RZT). It has been observed that standard RZT cannot predict the coupling effect of in-plane displacements for anisotropic multilayered structures, such as angle-ply laminates. The recent enhancement introduces two more zigzag functions in the local displacement field that overcome this drawback. According to the partially enforcement of transverse shear stress continuity at the interfaces, the zigzag functions are characterized. The equations of motion and consistent boundary conditions are derived through the D’Alembert principle and specialized for the linear free vibration analysis. Furthermore, the Ritz method in conjunction with the Gram-Schmidt orthogonal polynomials is used to assess the model’s performances when applied to the free-vibration analysis of plates with different types of boundary conditions. The numerical assessment investigates the influence of various design parameters, such as plate aspect ratios, boundary conditions and ply orientations.