High-Order Analysis of Unidirectional Sandwich Panels With Flat and Generally Piecewise Curved Faces and a “Soft” Core

The bending behavior of a unidirectional sandwich panel with flat and generally piecewise curved faces and a flexible core in the vertical direction is investigated. The studied panels consist of an upper flat face sheet, a core of a variable thickness, and a lower face sheet that can take any geometrical layout described by a piecewise analytical function. The core is assumed to be a two-dimensional elastic medium with vertical and shear rigidities only, and the faces are considered to have membrane and bending rigidities and are made of metallic or composite materials. The field equations and the boundary conditions are rigorously derived using the variational principle of virtual work. The continuity conditions between the various regions of the generally piecewise curved face are presented. Higher order effects in the form of nonlinear deformation distributions through the thickness due to flexibility of the core are incorporated in the proposed analysis. Numerical results in terms of deformations, stresses, and stress resultants are presented for some typical cases of piecewise flat-curved panels. The results demonstrate the capabilities and generality of the proposed model, especially in the ability to predict the high-order localized effects and the high stress concentrations that characterize these panels.