Higher-order layerwise laminate theory for the prediction of interlaminar shear stresses in thick composite and sandwich composite plates

A higher-order layerwise theoretical framework is presented, which enables prediction of the static response of thick composite and sandwich composite plates. The displacement field in each discrete layer through the thickness of the laminate includes quadratic and cubic polynomial distributions of the in-plane displacements, in addition to the linear approximations assumed by linear layerwise theories. In-plane and interlaminar shear stiffness matrices of each discrete layer are formulated and interlaminar shear stress compatibility conditions are subsequently imposed to ensure continuity of interlaminar shear stresses through the thickness. A Ritz-type exact solution is further implemented to yield the structural response of thick composite and sandwich composite plates. The advantage of the present formulation in comparison to linear layerwise theories lies in the small number of discrete layers used to model the thick composite laminate through-thickness and in the prediction of interlaminar shear stresses at the interface.