Twist in soft-core sandwich plates

This paper studies the twist behavior of soft-core sandwich plates. The paper adopts a comparative analytical approach, derives a geometrically nonlinear extended high-order sandwich plate theory, and compares this theory with the classical high-order one. The extended theory takes all stiffness components of the core and its Poisson effect into account and considers the direct contribution of the in-plane shear stresses in the core to the twist resistance mechanism. The classical high-order sandwich plate theory, which is presented for comparison, neglects the in-plane shear and normal stiffness of the core and attributes the twist mechanism to the composite action of the face sheets and to the ability of the core to resist out-of-plane shear and out-of-plane normal stresses. Both theories account for large displacements, moderate rotations, and small strains in the face sheets and serve as platforms for the development of specially tailored finite elements. Along with the development of the extended sandwich plate theory, the paper studies the twist behavior, compares the two theories, compares the results with experimental ones taken from the literature, and looks into the impact of the geometrical nonlinearity on the twist response.