Improved zigzag theories for laminated composite and sandwich plates with interlaminar shear stress continuity

In this present work, improved zigzag theories are developed for the flexural analysis of laminated plates using algebraic, hyperbolic, inverse trigonometric and trigonometric shear strain functions. The governing differential equations and boundary conditions of the structural system are obtained through the principle of virtual work. A generalized Navier closed form solution technique is applied for the flexural analysis of laminated plates. The present theories fulfill the transverse shear stress continuity and in-plane displacement continuity at each layer interfaces. Moreover, the present theories exhibit a constant variation of transverse displacement and parabolic variation of transverse shear stresses across the plate thickness. The tangential stress free boundary conditions are satisfied on the external surfaces of the panel; hence the necessity of artificial shear correction factor is ignored. The present theories consist of 5 unknowns as in the case of FSDT. Several numerical examples are carried out for a broad range of lamination sequence and geometric parameters. To reveal the potency and performance of the present models, numerical comparisons are made with the 3D elasticity solution and other numerical methods and it is observed that the present models perform very well for the static behavior of laminated plates.