Behavior of Unidirectional Sandwich Panels with a Multi-Skin Construction or a Multi-Layered Core Layout-High-Order Approach

The behavior of a unidirectional sandwich panel that consists of a multi-skin construction and a "soft" core is presented. In addition, a unidirectional sandwich panel with a core made of various layers, a multi-layered core, is discussed. The formulation is comprehensive, rigorous, and uses a variational approach that yields the field equations along with the appropriate boundary conditions for beams and unidirectional panels (wide beams). The governing equations for the two cases are presented for skins made of laminated composites with a general stacking sequence, and for a multi-layered core made of layers of isotropic or orthotropic materials. Typical panels that consist of a multi-skin construction are numerically studied. A unidirectional sandwich panel that has an edge with a cut-off is investigated and the involved stress concentration is examined as well. The effect of additional skin layers at mid height of the panel is presented and compared with an ordinary panel that consists of two skins. The multi-layered core layout is used to numerically study the effect of delamination between the layers of the core on the general behavior of the unidirectional sandwich panel and the stress concentration involved.