Papers by Keyword: Sandwich

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Authors: Yoko Okuwaki, Shigeo Yamaguchi
Abstract: We have studied a novel Peltier device having a metallic tip which is directly sandwiched between P-type and N-type thermoelectric materials. The tip can be heated and cooled directly driven by Peltier effect, resulting in high thermal response. In this study, we report the fabrication of a portable thermal cycler using a PN sandwich-structure Peltier device. The device has copper plates with minute fin to efficiently radiate heat.
Authors: Ping Lu, Xu Dong Liu, Xue Qiang Ma, Wei Bo Huang
Abstract: Constrained layer damping treatments such as sandwich beams are considered as the most efficient way of introducing vibration damping into a structure. The dynamic mechanical properties and damping behavior of a laminated sandwich composite beam inserted with a viscoelastic layer is investigated. A quantitative analysis of damping in the sandwich laminated composite beam has been conducted through the theoretical and experimental method. Traditional epoxy and new kind of polyurea viscoelastic layer are selected to analyze the damping properties. Results showed that the polyurea viscoelastic layer had good dumping capability. The effects of temperature, frequency of viscoelastic layer on vibration damping characteristics arc also discussed. They also demonstrate the great capability of laminated sandwich composites with embedded viscoelastic layer to considerably enhance structural damping.
Authors: Y. Aminanda, B. Castanie, J.J. Barrau
Abstract: A finite element model is proposed to determine the residual strength and the evolution of damage area of indented sandwiches structures with Nomex honeycomb core and metallic skins indented by a spherical indenter under longitudinal compression load (CAI). The honeycomb is represented by a grid of non-linear springs which its behavior law is obtained by performing simple transverse uniform compression test on a block of honeycomb alone.The comparisons between computation and test result show that the model can simulate accurately the form of damage geometry during indentation, its residual print when the load is relieved (relaxation) and the residual strength and the evolution of damage geometry during CAI.
Authors: Meng Kao Yeh, Tsung Han Hsieh
Abstract: The bending property and failure mechanism of sandwich beams were investigated. The multi-walled carbon nanotubes (MWNTs) were used as the reinforcement in the MWNTs/polymer nanocomposites and the epoxy and phenolic resins were used as the matrix. The MWNTs/polymer nanocomposites were used as the core materials of sandwich beams, which had faces made by graphite/epoxy laminates. In experiment, the hot press method was applied to fabricate the MWNTs/polymer nanocomposites and graphite/epoxy laminates. The weight percentage of MWNTs in core materials and the fiber orientation of face laminates were varied to assess their effects on the bending properties of the sandwich beams. The failure mechanism of sandwich beams with two kinds of polymer core materials was investigated. In analysis, the finite element method was used to obtain the bending behavior of the sandwich beams. The numerical results were in good agreement with the experimental ones.
Authors: Cheng Lin He, Jin Xiang Chen
Abstract: This report reviews biomimetic studies performed in China on the beetle forewing, noting that Chinese scholars studying bionics have substantially advanced various branches of biomimetic research in beetles. The report also proposes the development of branches of bionic research and establishes the foundation for corresponding experiments and theories. Then, using the A. dichotoma forewing as a an example, the cross-sectional shape, orientation of the laminated fiber layers, structure of the trabeculae, and respective mechanical properties of the forewing, as well as their biological significance, are reviewed. 1) The forewing has a lightweight border frame structure and an optimal design of variable cross-sections suitable for different positions, which achieves the specific second moment of inertia required for flight. 2) Due to the non-equiangular, laminated structure of the forewing, there are two types of tensile fracture morphologies: fiber breakage and residual bridging. This study demonstrates the anisotropy and the effectiveness of the forewings tensile strength by analyzing the orientation direction of the fibers. 3) The trabecular structure can be used to efficiently improve the peel resistance of the laminated composites. Based on the above points, possible directions for future work are also indicated in this paper.
Authors: Han Zhao, I. Elnasri, Hui Jian Li
Abstract: This paper presents a study of the strength enhancement under impact loading of metallic cellular materials as well as sandwich panels with cellular core. It begins with a review of likely causes responsible for the strength enhancement of cellular materials. A testing method using 60mm diameter Nylon Hopkinson pressure bars is used to investigate the rate sensitivity of various metallic cellular materials. In order to identify the factor responsible for the strength enhancement of those materials, an experimental analysis is performed on a model structure which is a square tube made of rate insensitive materials. Significant enhancement is experimentally observed under impact loading, whereas the crushing mode is nearly the same under both static and impact loading. 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.
Authors: Evgeny Barkanov, Andris Chate, Sandris Ručevskis, Eduards Skukis
Abstract: An inverse technique based on vibration tests to characterise isotropic, orthotropic and viscoelastic material properties of advanced composites is developed. An optimisation using the planning of experiments and response surface technique to minimise the error functional is applied to decrease considerably computational expenses. The inverse technique developed is tested on aluminium plates and applied to characterise orthotropic material properties of laminated composites and viscoelastic core material properties of sandwich composites.
Authors: Rafidah Hasan, Robert A.W. Mines, E. Shen, S. Tsopanos, Wesley J. Cantwell, W. Brooks, C.J. Sutcliffe
Abstract: This paper is a study of the drop weight impact behaviour of small sandwich panels of carbon epoxy skins with aluminium honeycomb and titanium alloy micro-lattice cores. A series of experimental tests have shown that the specific impactor penetration behaviours are similar for both cores. The reasons for this are a result of the detailed deformation and rupture behaviour of the two types of core. The deformation and rupture mechanisms of honeycomb and micro-lattice structures will be discussed in general terms, and these observations will be used to inform discussion of actual deformation and rupture in the panel tests. In this way, micro energy absorbing mechanisms will be related to panel performance, and conclusions on the way forward for improved penetration performance using other core materials and geometries will be identified.
Authors: Alexander Hackert, Claudia Drebenstedt, Tristan Timmel, Tomasz Osiecki, Lothar Kroll
Abstract: The combination of metals and fiber reinforced plastics is also known as hybrid metal composites. They offer the fusion of the good static mechanical properties of the fiber reinforced plastics and the good dynamic mechanical properties of the metal. For that reason, parts made of hybrid metal composites are predestined for the use as load relevant parts. The purpose of this study was to develop new technologies for semi finished hybrid metal composite materials. Thermoplastic Fiber-Reinforced Composites (TP-FRC) were arranged with new, isotropic, closed pore Aluminum Foam (AF) structures to an Extrinsically Combined Composite Sandwich (ECCS) by adhesive bonding. They form the basis for novel weight-optimized as well as cost-effective applications. The entire manufacturing process for the continuous semi-finished product was examined and verified according DIN EN 2563. This was done with regard to subsequent characterization by the specific bending modulus and specific bending stiffness. The examinations show a high bending stiffness and high strength structures combined with excellent damping properties at high damage tolerances. These are the most requested in automotive applications.
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