Arne Kildegaard

Local effects across core junctions in sandwich panels

Sandwich beams and panels with symmetric faces and cores of varying stiffness are investigated. The paper presents a theoretical and experimental study of the local effects that occur in the vicinity of intersections between cores of different stiffness in such sandwich panels. These local effects manifest themselves by a significant rise of the bending stresses in the faces in the vicinity of the core junctions. Closed-form estimates of the stress/strain fields induced by local effects are presented for sandwich beams and panels loaded in cylindrical bending. The accuracy of the derived closed-form estimates is verified experimentally for the case of a sandwich beam in three-point bending.

Large Deflections of Sandwich Plates: An experimental Investigation

Abstract An experiment was set up for the analysis of the large deflection of clamped sandwich plates. Surface strains and deflections were measured as a function of lateral load. It was found that the non-linear behaviour was more pronounced for strain than for deflection. The increase in strain in the tension face was shown to be less than the decrease in strain in the compression face. A finite element analysis of this problem gave comparable results.

Experimental study of a uniformly loaded curved sandwich beam

A sandwich curved beam subjected to a uniform loading is experimentally investigated. Load-deflection and thrust-deflection dependencies are shown to be nonlinear, while load-deformation dependencies for sandwich faces are found to be linear. A technical solution for implementation of the simple support is realized. An actual stiffness of the beam tie is measured experimentally and estimated theoretically.

Assessment of models for analysis of singly-curved sandwich panels

Abstract Overall behaviour of a simply-supported singly-curved shallow sandwich panel under lateral loading is considered. Three types of linear models — general shell, shallow shell and curved plate theories — are employed to describe a static overall behaviour of such a panel. The shallow panel with a constant curvature loaded by a uniform pressure is used as a trial case to assess the accuracy of the models. A nonlinear model for a panel of arbitrary shape under an arbitrary loading is developed on the basis of the curved plate theory. A closed-form nonlinear analytic solution for the panel of constant curvature under a uniform lateral pressure is obtained, and its accuracy is estimated. An experimental investigation of a sandwich beam under a uniform lateral loading is carried out, and the data obtained are compared with the theoretical calculations.

Overall behaviour of singly curved shallow sandwich panels : the case of general boundary conditions

Abstract The overall behaviour of the shallow sandwich panel with an arbitrary initial profile and general boundary conditions under an arbitrary load is discussed. The structural parameters of the panel that allow one to generalize description of the overall behaviour of the panel are introduced. The mathematical model based on the Reissner–Mindlin plate theory is developed, and the set of governing equations is derived. The implicit nonlinear and explicit linear solutions are obtained for the uniformly loaded panel with uniform curvature and similar boundary restraints. An analysis of the global stability is performed for panels that have general configurations. Three stability modes, namely stable deformation, symmetric and asymmetric snap-throughs are found possible. The influence of the structural parameters of the panel on its global behaviour is studied.

Analysis of Adhesive Bonded Generally Orthotropic Circular Cylindrical Shells

The problem of an adhesive bonded lap joint between two dissimilar orthotropic circular cylindrical laminated shells is considered. The principal directions of orthotropy do not have to coinside with the principal directions of curvature, and the external loads are allowed to be of non-axisymmetric type. The adhesive layer is modelled in two ways. The first approach assumes the adhesive layer to, behave as a linear elastic material. The second more realistic approach takes into account the predominantly inelastic behavior of many polymeric adhesives, and it is shown, that the non-linear behavior affects the adhesive stress distribution even at low load levels. The developed numerical solution procedures have been used to conduct a parametric study, and a few general design recommandations are given.