Papers by Keyword: Sandwich

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Authors: Feng Xian Xin, T.J. Lu, Chang Chen
Abstract: The transmission of sound through all-metallic sandwich panels with corrugated cores is investigated using the space-harmonic method. The sandwich panel is modeled as two parallel panels connected by uniformly distributed translational springs and rotational springs, with the mass of the core sheets taken as lumped mass. Based on the periodicity of the panel structure, a unit cell model is developed to provide the effective translational and rotational stiffness of the core. The model is used to investigate the influence of sound incidence angle and the inclination angle between facesheet and core sheet on the sound transmission loss (STL) of the sandwich structure. The results show that the inclination angle has a significant effect on STL, and sandwich panels with corrugated cores are more suitable for the insulation of sound having small incidence angle.
Authors: Ahmed Abbadi, Z. Azari, Salim Belouettar, J. Gilgert, G. Pluvinage
Abstract: Problems for load carrying elements reside mainly in buckling, embrittlement and corrosion. These problems can be mainly solved by introduction of composite materials of a sandwich type. These materials ally lightness, rigidity and resistance to the corrosion. For the design of a large number of applications, static and cyclic properties are necessary. In this paper, first static and fatigue tests on four points bending of four types sandwich panels have been performed. Load/displacement and S-N fatigue curves are presented and analysed. Fatigue failure and damage modes are observed with an electronic microscope and are discussed. Numerical simulation applied to the static tests is compared to the experimental results. The second is to address such fatigue behaviour by using a damage model and check it by experimentation. This fatigue damage model is based on stiffness degradation, which is used as a damage indicator. Four non-linear cumulative damage models derived from the chosen stiffness degradation equation are examined with assumption of linear Miner’s damage summation. Predicted results are compared with available experimental data.
Authors: Akmaluddin, Suryawan Murtiadi, Zaedar Gazalba
Abstract: This study is aimed to discuss structural behavior of steel reinforced sandwich concrete beams (SWB) consisted of skins and a core. The skins were made of ordinary concrete and a core was of pumice lightweight concrete. The SWB skin compressive strengths of 30 MPa and the core compressive strength of 15 MPa were considered. Twelve SWB specimen of 150x250x2500 mm with 50 mm skin thickness and 150 mm core thickness were cast and tested after curing process under flexural points loading as simply supported beams. All the beams considered were reinforced with 3D12 mm deformed bar and 8 mm stirrups with 3 spacing variations. Shear span depth ratio (a/d) of 1.8, 2.3, 2.8, and 5.4 were also considered to reflect the behavior between short and slender beams. Results showed that the flexural behavior of sandwich beams were identical with normal or lightweight concrete beams behavior. Ultimate moment of beam section slightly increased with increasing the shear span to depth ratio, which were varies between 1.26 and 2.31 of the calculated moment. The yield moment to the ultimate moment ratio vary between 0.83 and 0.99. The ductility was increased with the decreased shear reinforcement spacing. The shear strength increased as the spacing of shear reinforcement decreases in almost all a/d variations. Shear strength was also increased with the increase of a/d ratio for short beam and the other hand shear strength decreased with the increasing a/d.
Authors: Claudia Girjob, Gabriel Racz, Octavian Bologa, Cristina Biris
Abstract: There is a continuing interest in using laminated materials for the production of lightweight parts, the resulting parts having the same functionality and even an increased stiffness and length of operation compared to conventional materials. The present paper aims to study the forming behavior of the laminated materials that requires the unfolding of tests to determine the tensile mechanical properties and the intrinsic properties, determining the forming limit curves by means of the Nakajima test and the analysis of the behavior at unconventional incremental forming.
Authors: Jin Liang, Dong Yang Zhang, Shu Jiang Ding
Abstract: In this work, we prepared the sandwich-like carbon@SnO2@carbon hollow spheres by templating against polystyrene spheres. The hollow spheres are characterized by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD). The electrochemical performance as the anodes of lithium-ions batteries are studied by the cyclic voltammogram (CV) and galvanostatic discharge-charge voltage tests. Because of the interesting structure, the as prepared carbon@SnO2@carbon hollow spheres deliver a reversible capacity of 492 mA h g-1 after 50 cycles at a high current density of 400 mA g-1.
Authors: M. Ashraf Sheikh
Abstract: The present study investigated the effect of copper and nickel together on ductile iron. Ductile iron was produced by the sandwich method using induction furnace installed at local commercial foundry. Heats without copper & nickel and with copper 0.5 wt% and 1.0 wt% nickel in combination were made. Tensile samples were machined from Y Block castings. Tensile test was performed to find out the effect of copper and nickel together on tensile strength of ductile iron. Effect of austempering heat treatment was also studied to find out the effect of copper and nickel in combination on tensile strength. The samples were austenitized at 900 oC for one hour and austempered at 270 oC and 370 oC. It was found that with the addition of copper and nickel the tensile strength of ductile iron increased. The tensile strength was more than double when the samples were subjected to austempering heat treatment at 270°C.
Authors: Chang Liang Li, Da Zhi Jiang, Jing Cheng Zeng
Abstract: In this work, the hybrid fabrics of carbon and quartz fibers as filters were adopted in PMI core sandwich structures for low-observable radomes. The advantages of fabric composite frequency selective surfaces (FCFSSs) are easily fabricated by braiding and shaped into curved surfaces. This paper mainly studied the electromagnetic (EM) transmission characteristics of the low-observable radome wall with composite FSS by 3-dimensional electromagnetic analysis software. First of all, the accuracy of the simulation model composed of up and down composite face sheets, a layer of composite FSS and PMI core was validated by comparing with experimental results. Then, the studies on electromagnetic transmission characteristics of the sandwich structure with composite FSS and the sensitivity analysis about the thickness and permittivity of face sheets and PMI core were carried out. The results show that the sandwich structure with single layer composite FSS can realize the function of frequency selection, limit the reflection at the resonance frequency and decrease the sensitivity of EM transmission loss about the thickness of sandwich structures.
Authors: Moussa Karama
Abstract: Thick composites are increasingly used in the design of mechanical structures. Combined with low weight, they are generally resistant structures, which can support importante loads. In addition, depending on the number and nature of the materials used, it is possible to adapt properties for specific applications (damping structures).This work proposes the establishment of a new theoretical model of multilayer beam. The model, which is simple and easy handling, is intended for the subsequent establishment of a finite element. The goals are:improve the refinement of the transverse displacement and transverse shear, avoiding the calculation of transverse shear, the use of correction factors,keep only the usual displacement,test the accuracy of the model compared with models from the literature (for an equivalent single-layer approach).The proposed approach is of the kinematics, the form adopted for the displacement field is justified from a dimensional point of view, by the equations of elasticity. The equations of motion and boundary conditions are obtained by applying the principle of virtual power.The validity of the model is tested on problems for which solutions (obtained by previous theories) exist.
Authors: Mitra Djamal, Ramli
Abstract: In recent decades, a new magnetic sensor based on magnetoresistance effect is highly researched and developed intensively. GMR material has great potential as next generation magnetic field sensing devices. It has also good magnetic and electric properties, and high potential to be developed into various applications of electronic devices such as: magnetic field sensor, current measurements, linear and rotational position sensor, data storage, head recording, and non-volatile magnetic random access memory. GMR material can be developed to be solid state magnetic sensors that are widely used in low field magnetic sensing applications. A solid state magnetic sensor can directly convert magnetic field into resistance, which can be easily detected by applying a sense current or voltage. Generally, there are many sensors for measuring the low magnetic field, such as: fluxgate sensor, Hall sensor, induction coil, GMR sensor, and SQUID sensor. Compared to other low magnetic field sensing techniques, solid state sensors have demonstrated many advantages, such as: small size (<0.1mm2), low power, high sensitivity (~0.1Oe) and good compatibility with CMOS technology. The thin film of GMR is usually prepared using: sputtering, electro deposition or molecular beam epitaxy (MBE) techniques. But so far, not many researchers reported the manufacture of thin film of GMR by dc-Opposed Target Magnetron Sputtering (dc-OTMS). In this paper, we inform the development of GMR thin film with sandwich and spin valve structures using dc-OTMS method. We have also developed organic GMR with Alq3 as a spacer layer.
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