Comparative study and mechanical properties of several composite sandwich structures
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https://www.eduzhai.net International Journal of Composite Materials 2015, 5(1): 1-8 DOI: 10.5923/j.cmaterials.20150501.01 Comparison Study and Mechanical Characterisation of a Several Composite Sandwich Structures Jamal Arbaoui1,2,*, Yves Schmitt2,3, Jean-Luc Pierrot2, François-Xavier Royer2 1ENSTA Bretagne, MSN/LBMS/DFMS, 2 rue François Verny, Brest, France 2LPMD/Université de Metz, 1 bld Arago, Metz, France 3P.A. TECHNOLOGIES, 9 rue des Balanciers, Thionville, France Abstract Composite sandwich structures have excellent properties and they are widely used in the fields of high technology such as aeronautics and astronautics, etc. Investigations of the mechanical properties of composite sandwich structures play a vital role in determining their applicability in various engineering fields. In this study, we have developed a new core material, which is an original cellular composite based on polystyren cells named YmaCell. Bending and crash properties of YmaCell are determined and compared with a polypropylen honeycomb and a thermoplastic foam panel. The results show that the rigidity of the cellular composite YmaCell is better than that of the polypropylen honeycomb structures and the thermoplastic foam. The chemical bonds between the skins are likely to be a major factor for the higher performances of the cellular composite. Keywords Composite, Short fibres, Sandwich structures, Crash, Bending 1. Introduction Sandwich panels typically consist of two thin face sheets or skins and a lightweight thicker core. Commonly used materials for face sheets are composite laminates and metals, while cores are made of metallic and non-metallic honeycombs, cellular foams, balsa wood or trusses. The face sheets are typically bonded to the core with an adhesive, and carry most of the bending and in-plane loads. The core provides the flexural stiffness and out-of-plane shear and compressive strength. The structural performance of sandwich panels depends not only on the properties of the skins, but also on those of the core, the adhesive bonding the core to the skins, and the geometrical dimensions of the components. Sandwich composites with cellular core are widely employed in modern mechanical design, not only in the field of aeronautical constructions, where they have been developed initially, but also in the fields of on-land transportation and marine constructions. Because of their characteristic features, such as the high flexural resistance and stiffness , the high impact strength [2, 3], the high corrosion resistance and the low thermal and acoustics conductivity [5, 6, 7], sandwich structures are in fact preferred over conventional materials in various industrial * Corresponding author: firstname.lastname@example.org (Jamal Arbaoui) Published online at https://www.eduzhai.net Copyright © 2015 Scientific & Academic Publishing. All Rights Reserved applications. Although large numbers of research projects have been performed by various authors, the design of structural elements made from sandwich composites is often a difficult task. This is mainly because a reliable strength prediction needs the preliminary knowledge of the mechanical behavior of skins and core, as well as of the peculiar damage mechanisms [8, 9, 10], and failure criteria that can be used under a complex loading. In the last years, the research and development on a large range of cellular composites has been explored. In nature cellular structures can be found in plants and bird bones. Such structures have been reproduced so closely as possible to the natural ones. The basic principal for the production of such a materials is the association of a sophisticated system of stiff-walled, tree-dimensional cells with a short-fibred composite material. In this paper a sandwich element with a novel cellular core named YmaCell are developed. Bending and crash properties of YmaCell are determined and compared with a polypropylene honeycomb and a thermoplastic foam panel. The panels are covered with different composite walls. 2. Sandwich Material A typical simply supported sandwich panel consists of two thin faces with a thickness of t, separated by a light and a weaker core of thickness hc, as illustrated in Fig.1. The overall depth of the panel is h and the width b. The faces are typically bonded to the core to provide a load transfer 2 Jamal Arbaoui et al.: Comparison Study and Mechanical Characterisation of a Several Composite Sandwich Structures mechanism between the main components of the sandwich panel. Figure 2. The four-point bending test  3. Experimental Procedure Figure 1. A structure of a sandwich composite  The flexural rigidity for a sandwich beam, denoted as D, is the sum of the flexural rigidities of the faces and the core measured with respect to the centroidal axis of the entire section and can be expressed as: D = E f bt3 6 + E f btd 2 2 + Ecbhc3 12 = 2Df + D0 + Dc (1) Where Ef and Ec are the Young’s modulus of the face sheet and core, and d = t + hc. Df is the bending stiffness of a face sheet about its own neutral axis, D0 is the stiffness of the face sheets associated with bending about the neutral axis of the entire sandwich, and Dc is the stiffness of the core . Since the core is stiff in shear but soft generally, its Young’s modulus is much smaller than that of the face sheet. By assuming Ec <
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