A refined zigzag nonlinear first-order shear deformation theory of composite laminated plates

A refined nonlinear zigzag shear deformation theory of composite laminated plates is presented using a modified mixed variational formulation. The theory accounts for continuous piecewise layer-by-layer linear variation approximation in the thickness direction for the displacements. Moreover, it includes piecewise stress distributions satisfying the continuity conditions at the layer interfaces and the surface conditions. The advantages of this theory are that it recovers the interlaminar stresses, and does not need any shear correction factor used in other first-order theories. To assess this theory, the bending problems of symmetric and antisymmetric cross-ply laminated plates are solved. Some numerical results for the deflection and stresses are compared with their counterparts in the literature obtained due to three-dimensional elasticity solution and higher-order laminate theories. It is found that the present theory predicts the local and global responses of the laminated plates with excellent accuracy.