A modified zig-zag theory was used to investigate the bending behavior of composite plates and sandwich structures. The theory is based on the first-order shear-deformation theory on some piecewise linear functions for in-plane displacements. This theory does not depend on the shear correction factor and can be applied to various engineering problems associated with the structural dynamics. The nonlinear strain terms in the von Kármán compatibility equation were taken into account to calculate accurate results at large deformation. The governing equations and associated boundary conditions were derived using the principle of virtual work. The calculated numerical results are compared with those of other theories, and an excellent agreement between them was found. The figures and tables presented illustrate the superiority of the model considered in predicting the stress and displacement fields. The model proposed is applicable to nonlinear problems with large deflections.
