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A new coupled efficient layerwise higher-order theory is presented lot analysis of hybrid piezoelectric composite plates with the aim of predicting transverse shear stresses directly from the constitutive equations. The theory is developed by superposing layerwise quadratic and cubic terms on the third-order zigzag approximations of the existing zigzag theory. The electric potential is assumed to be quadratic actress the layers. By satisfying the interface continuity conditions for each of the two local terms separately and enforcing the conditions on the transverse shear stresses at layer interfaces and top and bottom surfaces, the number of displacement unknowns is reduced to nine. Comparisons with the three-dimensional exact solutions reveal that the present theory is a significant improvement over the existing zigzag theory for elastic and hybrid composite plates. It yields superior results, not only for transverse shear stresses, but also for other response entities, including the layerwise higher-order variations of in-plane displacements and nonuniform distribution of deflection under electric potential load. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

An improved efficient zigzag theory (IZIGT) and an improved third order theory (ITOT) are presented for laminated circular cylindrical shells and shell panels under thermal loading. The transverse deflection is approximated nonuniformly to explicitly account for the transverse strain due to temperature. The inplane displacements are modelled in ITOT to have global cubic variation across the thickness and are modelled in IZIGT to have additional layerwise zigzag linear variation. The number of primary variables is reduced to 5 by imposing conditions on transverse shear at outer and inner surfaces for ITOT and also at layer interfaces for IZIGT. The governing equations and boundary conditions are derived using the principle of virtual work. The IZIGT, ZIGT, ITOT and TOT are assessed in comparison with exact 3D thermoelasticity solution for simply supported shells and shell panels of different lay-ups. The comparison reveals that IZIGT and ITOT are an improvement over ZIGT and TOT respectively, and in general, IZIGT is more accurate than ITOT for thermal loading. [ABSTRACT FROM AUTHOR]