Efficient Global Zigzag Theory for Elastic Laminated Plates

An efficient global zigzag theory (GZIGT) is developed for elastic laminated plates, by approximating the in-plane displacements by a cubic expansion in thickness coordinate along with a global zigzag function, which takes values ±1 at successive interfaces. The deflection is approximated to account explicitly for transverse thermal strain. The displacement variables are reduced to five, the same as used in first-order shear deformation theory, by imposing the conditions on transverse shear at three a priori selected interfaces/faces. A third order theory (TOT1) is also developed with similar expression of deflection. GZIGT and TOT1 are assessed by comparison with exact three-dimensional solutions for simply-supported square plates for sinusoidal pressure and thermal loads, natural frequencies and buckling. In general, GZIGT yields good results for two-ply, three-ply and four-ply composite plates, but it is inaccurate for a highly inhomogeneous test plate.