Intensity of Local Effects at the Core Junctions in Sandwich Panels
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Springer 2006
Intensity of Local Effects at the Core Junctions in Sandwich Panels E. BOZHEVOLNAYA1,j and M. PANTKE2 1
Institute of Mechanical Engineering, Aalborg University, Pontoppidanstræde 101, 9220 Aalborg East, Denmark. e-mail: [email protected] 2 Department of Mechanical Engineering, THF Berlin, Luxemburger Straße 10, 13353 Berlin, Germany. e-mail: [email protected] (Received 21 February 2005; accepted 11 October 2005) Abstract. Local effects that occur in the vicinity of junctions between different cores in sandwich panels subjected to the in-plane axial force and bending moment are considered. These local effects manifest themselves in a rise of locally induced bending normal stresses in the sandwich faces and shear and normal stresses in the cores in the near vicinity of the core junctions. Intensity of the local effects is measured experimentally for a representative sandwich beam subjected to both types of loadings. The numerical simulations are performed using Finite Element Analysis, and they reveal significant rates of stress concentrations in the faces and cores adjacent to the core junctions. The intensity of the local effects is dependable on the geometry and elastic properties of the sandwich faces and a degree of dissimilarity of elastic properties of the adjoined cores. Key words: local effect, core junction, sandwich panel.
1. Introduction Sandwich beams/panels, formed from two thin and stiff panels, so called faces, and separated by a thick and compliant core, are very advantageous in many structural applications such as space, aircraft, automotive, marine, building and energy industries. The stiff faces are effective in withstanding the bending loads applied to the panel/shell, whilst the compliant core offers a high resistance to the shear loads. High stiffness-to-weight and strength-to-weight ratios are inherent to sandwich panels. A large variety of applied materials and a wide assortment of developed manufacturing methods allows a purposeful design tailoring of sandwich components and a usage of different materials and geometries. This increases the structural performance of any particular lightweight structure under specific loading conditions. However, in spite of the many advantages of using sandwich components, there are a lot of unsolved problems. Being excellent structural elements with respect to their global load-bearing capacity, sandwich panels are particularly j
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E. BOZHEVOLNAYA AND M. PANTKE
vulnerable with respect to local effects. The practical functionality of sandwich panels implies a possibility to assemble (join) them and also to introduce various rigging/furnishing appliances. This involves the use of cores of higher stiffness, edge and corner stiffeners, backing plates, through-the-thickness and partly potted inserts, etc. into the sandwich panel [1, 2]. A mismatch of the elastic properties of the adjoined cores in the same sandwich panel inevitably leads to local stress concentrations in and around any core jun
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