Papers by Keyword: Sandwich

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Authors: Alexander D. Fergusson, Amit Puri, Andrew Morris, John P. Dear
Abstract: Composite sandwich structures are finding increasingly widespread use in fields ranging from aerospace and wind turbines to sports applications such as skis and surfboards. The high specific stiffness that composite sandwich structures can provide lends them well to these applications. However, the operational environment of these structures is frequently aggressive and often results in damage during service. The extent and effect of damage incurred is an important factor in the design and maintenance of composite sandwich structures. Failure of an individual component can be catastrophic for the rest of the structure. The purpose of this investigation was, firstly, to ascertain whether DSP was a viable technique for determining strain fields within composite sandwich structures. Secondly, to determine whether four point flexure would give rise to pure flexure between the central rollers, and if not, to understand what load conditions were present. This investigation was also carried out with a view to extend the investigation into the effect of defects on composite sandwich structures manufactured by RIFT. The grounds for selection of composite sandwich structures normally lie in their flexural performance. Reliable and accurate quantitative testing methods for evaluating the flexural performance of sandwich panels are needed if composite sandwich structures are to be used safely and effectively. In addition, methods to determine the effect of damage and defects on flexural behaviour of sandwich structures is particularly important for designing the repair and maintenance regimes of composite sandwich components.
Authors: Zakaria Ibnorachid, Khalid El Bikri, Lhoucine Boutahar
Abstract: The aim of the present work is to study the linear free symmetric vibration of three-layer sandwich beam using the energy method. The zigzag model is used to describe the displacement field. The theoretical model is based on the top and bottom layers behave as Euler-Bernoulli beams while the core layer as a Timoshenko beam. Based on Hamilton’s principle, the governing equation of motion sandwich beam is obtained in order to calculate the linear frequency parameters. Two types of boundary conditions simple supported-simple-supported (SS-SS) and clamped-clamped (C-C) under the influence of materials properties and geometrical parameters are studied. The validation of results is done by comparing with another studies, which available in the literature and found good agreement between the studies.
Authors: Albert U. Ude, Ahmad K. Ariffin, Che H. Azhari
Abstract: This paper describes the result of an experimental investigation on the impact damage on woven natural silk/epoxy composite face-sheet and PVC foam core sandwich panel. The test panels were prepared by hand-lay-up method. The low-velocity impact response of the composites sandwich panels is studied at three energy levels of 32, 48, and 64 joule respectively. The focus is to investigate damage initiation, damage propagation, and mechanisms of failure. It was observed that absorption energy capability decreased as impact energy increased. There was deflection on each impact load configuration at some point but their margin was insignificant. Physical examination of the specimen show that damage areas increased with increase in impact load. The novelty of this research is the use of woven natural silk fabric as a reinforcement fibre.
Authors: Christian Fiebig, Michael Koch
Abstract: The lightweight potential of components made of fiber-reinforced plastic can be enhanced by use of sandwich composites. So far, limited dynamic properties of plastic-based foams have prevented the use of sandwich composites in machine applications. The combination of closed-cell aluminum foam (ALF) and carbon fiber reinforced plastic (CFRP) provides a solution to this obstacle. Aluminum foam is characterized by favorable damping properties with minimum weight and CFRP provides high strength and stiffness at similarly low density. This paper deals with the design of a hybrid sandwich composite and its interpretation by using customized FEM simulations.Producing this kind of a sandwich composite in an economic production process presents a major challenge. Thus, a method has been developed that prevents excessive penetration of the resin into the pores of the aluminum foam. A high volume fraction of the resin in the foamed sandwich core would increase density and negatively influence damping properties. The implementation of a barrier layer will avoid this penetration. A DoE was developed and RTM process parameters were varied with the objective of achieving the highest specific bending stiffness. In preliminary experiments the appropriate range of injection pressure, mold temperature, and pressure force was determined. Tests with a nonwoven fabric could prevent the resin from infiltrating into the aluminum foam. Mechanical properties of the sandwich composite are only marginally affected.A model was developed to calculate the obtainable sandwich composite properties. The calculation method considers both the characteristics of the aluminum foam and the CFRP anisotropy. Based on this model a reliable calculation of the applied load could be accomplished. The design of the sandwich composite was targeting at high stiffness and determination of the natural frequency. Parallel to calculations, tests on specimen were performed and the obtained results were included into the calculation as part of the material model.
Authors: Robert A.W. Mines, S. McKown, S. Tsopanos, E. Shen, Wesley J. Cantwell, W. Brooks, C.J. Sutcliffe
Abstract: This paper discusses the penetration behavior of fully supported sandwich panels with micro-lattice and foam cores, and composite skins. This behaviour is of importance during foreign object impact and perforation of sandwich structures. Experimental results are given for quasi-static penetration of micro-lattice and foam blocks, and it is shown that these two cellular materials are comparable. Experimental results are also given for drop weight penetration of fully supported skinned panels, and it is shown that skin failure and core penetration are also similar for the two core materials. It is concluded that there is scope for improving the performance of micro-lattice structure and so making such material superior to that of aluminium foam.
Authors: E.E. Shalyguina, Kyung Ho Shin, M.A. Karsanova, O.A. Shalyguina, I.A. Pogrebnaya
Authors: K. Saidani, Kamal Ait Tahar, S. Merakeb
Abstract: A sandwich structure is obtained from two skins or soles, with good mechanical characteristics, bonded to a core made of a lightweight material of low resistance. Glued to a core made of a lightweight material of low resistance. The strength and modulus of elasticity of the skin condition the bending behavior of a sandwich. Bending, the skins of the sandwich are solicited in traction and in compression, while the core is subjected to shear. Our study focuses on the experimental characterization under flexural load of new composite sandwich combined. The sandwich proposed constituted of two skins armed by metal grids impregnated with epoxy matrix type STR and souls composed of hybrid corrugated cardboard reinforced by fabric. Several configurations of souls made from cardboard cellulosic and fabrics were taken into account. An experimental and numerical investigation is conducted to analyze the behavior of these structures. The results show that the failure mode is strongly influenced by the stacking sequence considered.
Authors: Li Wan, Wei Qing Liu, Hai Fang
Abstract: Paulownia wood was drilled with some glass fibers fulfilled in the holes, which could be the core of the sandwich structures. In the manufacture processing, the fibers and resins left in the holes formed composite columns and merged with the facesheets. These could enhance the mechanical behavior of paulownia wood sandwich structures. Double cantilever beam(DCB) tests and bending analysis with finite element method were carried out. The improvement from the composite columns gave little contribution to bending behavior, but significant contribution to interfacial properties.
Authors: Thamir Aunal Deen Mohammed Sheet Almula, Yahya Mohd Yazid, Ayob Amran
Abstract: In this investigation, the mechanical behavior of sandwich hollow cylinders under internal pressure is carried out numerically. Functionally Graded (FG) foam core sandwich hollow cylinders are fabricated by employing filament winding technique with [±55] carbon fiber/epoxy as skins with the FG foam core made using centrifugal casting technique of polyurethane foam with epoxy resin. A finite element (FE) model is developed employing a FE commercial code to determine the stresses and deformations. Numerical analysis is performed to find the effect of one particular functional grading on the deformation and stresses. The results are compared with similar tubes using uniform PU foam core. The results show that grading the foam core affects the displacements and stresses in a significant way. The FG foam sandwich core tube possesses a lower displacement magnitude and higher maximum stresses taking into account the mass of the two types of pipes and rigidity compared to uniform PU foam core under internal pressure of 10 MPa.
Authors: Han Zhao, I. Nasri, Hui Jian Li
Abstract: This paper presents a experimental study of the strength enhancement under impact loading of metallic cellular materials as well as sandwich panels with cellular core. A testing method using 60mm diameter Nylon Hopkinson pressure bars is used to investigate the rate sensitivity of various metallic cellular materials as honeycombs, foams. Finally, an inversed perforation test on sandwich panels with an instrumented pressure bar is also presented. Such a new testing setup provides piercing force time history measurement, generally inaccessible. Testing results show a notable enhancement of piercing forces, even though the skin aluminum plates and the foam cores are nearly rate insensitive.
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