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

Abstract

The bending behavior of a unidirectional sandwich panel with flat and generally 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 variable thickness, and a lower face sheet that can take any geometrical layout described by an analytical function. The core is assumed a two-dimensional elastic medium with shear and transverse vertical rigidities only, and the face sheets are considered as membrane and bending members made of metallic or composite materials. The term unidirectional refers here either to a beam (narrow panel) or to a wide beam (panel) undergoing a cylindrical bending. The field equations and the boundary conditions are derived via the variational principle of the virtual work and transformed from the local polar coordinate system of the curved face into the global Cartesian one. Higher order effects due to flexibility of the core in the form of nonlinear deformation fields are incorporated in the proposed analysis as a result of the closed-form solution of the field equations and are not postulated a priori. Numerical results in terms of deformations, stresses, and stress resultants are presented for some typical cases of flat-curved panels. The effect of a wide range of layouts, various boundary conditions, and the influence of manufacturing imperfections in the form of initially wrinkled face are investigated. The results demonstrate the capabilities and generality of the proposed model and present its ability to predict the high-order localized effects that characterize such panels.

New 2D Approach and Solution to the Static Transverse Bending Problem for a Sandwich Strip with Realistic Clampings of the Edges

“…The idea of satisfying the end boundary conditions (6) by the fields ( 14) and (19) was first proposed by the present author [23]. For the sake of easier understanding of this paper the idea is briefly outlined here.…”

“…Anyway, both solution shown in Figure 1 and its mathematical representation introduced in this paper ensure existence of the bending moment at the edges and due to this one may say to some extent about edge clamping. It is noted that this kind of real fastening (''clamping'') of the sandwich structure to the edge supports cannot be included in the existing approximate analytic models [18][19][20][21][22] while many authors [23][24][25][26] claim that including the realistic edge conditions is very important. Moreover, majority of the approximate models mentioned above are only valid for the classical sandwich structures consisting of two faces and the core.…”

Nonlinear dynamic analysis of tapered sandwich plates with multi-layered faces subjected to air blast loading

“…Vel et al (2005) developed a tapered sandwich theory that predicts the stresses and deflection of tapered sections and tested on bending of sandwich panels with laminated anisotropic facings. Rabinovitch and Frostig (2001) studied about the bending behavior of a unidirectional sandwich panel with curved faces and a flexible core with variable thickness. There had been also methodological studies about static analysis of sandwich plates with variable thickness by small deflection theory (Paydar and Libove 1988;Wang 1998).…”

On application of catenary principles to sandwich structure design—Sandwich/ catenary hybrid beams under uniformly distributed load

“…Frostig and Peled [9] employed a higher-order formulation to study stresses in transition zones between parallel-face and tapered sections of a sandwich beam. Using the same principles for derivation of displacement field equations, Rabinovich and Frostig [10] described sandwich panels/wide beams with one flat face-sheet and one face-sheet with a generally curved shape, and it would appear that the sandwich/catenary hybrid falls in this category. The methodology, however, relies on nonzero core thickness throughout the panel/ beam length; several of the governing equations involve division by zero if the core thickness vanishes (which is an inherent feature of the sandwich/catenary hybrid at the external supports, see Figure 1(c)).…”