• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.444-447
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• 2008

A sandwich plate with a truss core is composed of two face sheets and a truss core between the face sheets. In this paper, a metallic sandwich plate with a pyramidal truss core is investigated numerically, for its deformation and energy absorption ability under dynamic loading. To find the effect of mechanical properties on crashworthiness in the sandwich plate with a pyramidal truss core, various pyramidal cores were simulated and investigated. It appears that relative density and shear modulus of a pyramidal truss core effect the change of energy absorption.

• Transactions of Materials Processing
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• v.19 no.7
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• pp.411-415
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• 2010

A sandwich panel which is comprised of truss cores faced with solid face sheets is lightweight and multi-functional. So it is widely used to not only structural material but also heat transfer media in transportation field such as airplane, train and vessel. There are various core topologies such as pyramidal and tetrahedral truss, square honeycombs and kagome truss. The study focused on analytical approach to optimize compression and shear quality of the unit cell of PCM with pyramidal configuration. With various unit cell models which have the same core weight per unit area but different truss member angle, analytical solution for effective stress ($\bar{\sigma},\bar{\tau}$), peak stress ($\bar{\sigma}_{peak},\bar{\tau}_{peak}$) by yielding and buckling, relative density ($\bar{\rho}_c$) and effective stiffness ($\bar{E},\bar{G}$) have been computed and compared each other. With this approach, the most optimal core configuration was predicted. The result has become the efficient guidelines for the design of PCM core structure.

• Advances in aircraft and spacecraft science
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• v.9 no.5
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• pp.377-400
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• 2022

The aim of this work is a numerical comparison (FEM) between lattice pyramidal-core panel and honeycomb core panel for different core thicknesses. By evaluating the mid-span deflection, the shear rigidity and the shear modulus for both core types and different core thicknesses, it is possible to define which core type has got the best mechanical behaviour for each thickness and the evolution of that behaviour as far as the thickness increases. Since a specific base geometry has been used for the lattice pyramidal core, the comparison gives us the opportunity to investigate the unit cell strut angle giving the higher mechanical properties. The presented work considers a detailed FEM modelling of a standard 3-point bending test (ASTM C393/C393M Standard Practice). Detailed FEM modelling addresses to detailed discretization of cores by means of beam elements for lattice core and shell elements for honeycomb core. Facings, instead, have been modelled by using shell elements for both sandwich panels. On lattice core structure, elements of core and facings are directly connected, to better simulate the additive manufacturing process. Otherwise, an MPC-based constraint between facings and core has been used for honeycomb core structure. Both sandwich panels are entirely built of Aluminium alloy. Prior to compare the two models, the FEM sandwich panel model with lattice pyramidal core needs to be validated with 3-point bending test experimental results, in order to ensure a good reliability of the FEM approach and of the comparison. Furthermore, the analytical validation has been performed according to Allen's theory. The FEM analysis is linear static with an increasing midspan load ranging from 50N up to 500N.

• Elastomers and Composites
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• v.51 no.4
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• pp.275-279
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• 2016

Additive manufacturing or 3D printing is a new manufacturing process and its application is getting growth. However, the product qualities such as mechanical strength, dimensional accuracy, and surface quality are low compared with conventional manufacturing process such as molding and machining. In this study not only mechanical characteristics of polymer sandwich panel having three dimensional core layer but also mechanical characteristics of core layer itself were analyzed. The shape of three dimensional core layer was pyramidal kagome structure. This core layer was fabricated by two different methods, injection molding with PP resin and material jetting type 3D printing with acrylic photo curable resin. The material for face sheets in the polymer sandwich panel was PP. Maximum load, stiffness, and elongation at break were examined for core layers fabricated by two different methods and also assembled polymer sandwich panels. 3D printed core showed brittle behavior, but the brittleness decreased in polymer sandwich panel containing 3D printed core. The availability of 3D printed article for the three dimensional core layer of polymer sandwich panel was verified.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.5
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• pp.623-631
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• 2011

Metallic sandwich panels based on a truss core structure have been developed for a wide range of potential applications with their lightweight and multi-functionality. Structural performance of sandwich panels can be predicted from the studies on mechanical behavior of a unit cell of truss core structures. Analytical investigations on the unit cell provide approximated guidelines for the design of overall core structures for a specific application in short time. In this study, the effects of geometrical parameters on mechanical behavior of a pyramidal shape of unit cell were investigated with analytical models. The unit cell with truss member angle of 45 degree was considered as reference model and other models were designed to have the same weight and projected area but different truss member angle. All truss members were assumed to be connected with pin joint in analytical models. Under the assumptions, the equivalent strength and stiffness of the unit cell under compressive and shear loads were predicted and compared. And finally, the optimum core member angle to have maximum mechanical property could be calculated and verified with FE analysis results.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.11a
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• pp.109-110
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• 2007

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.1209-1210
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• 2011

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.262-265
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• 2007

Metallic sandwich plates constructed of two face sheets and low relative density cores have lightweight characteristics and various static and dynamic load bearing functions. To predict the formability and performance of these structured materials, a computationally efficient FE-analysis method incorporating virtual equivalent projected model has been newly introduced for analysis of metallic sandwich plates. Two dimensional models using the projected shapes of 3D structures have the same equivalent elastic-plastic properties with original geometries including anisotropic stiffness, yield strength and linear hardening function. The projected shapes and virtual properties of the virtual equivalent projected model have been estimated analytically with the same equivalent properties and face buckling strength of 3D pyramidal truss core.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.6
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• pp.697-702
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• 2017

A preliminary study was carried out to investigate the feasibility of replacing honeycomb cores with pyramidal truss cores in the doors of urban transit railway vehicles. The doors in current operation are sandwich structures comprising a honeycomb core and reinforcements between two facesheets. The structural requirements of doors for urban transit vehicle are specified in the KRS and KRT and standards, according to which the deflections from three-point bending tests must be limited. To this end, two types of pyramidal truss cores with equivalent mass to a honeycomb core were designed. The structural stiffness of doors with pyramidal truss cores and honeycomb cores were numerically calculated via finite element analysis. The three-point bending models were constructed and simulated, and then the calculated deflections were compared with the requirements specified in the regulations. The results show that doors with pyramidal truss cores satisfied the stiffness requirements, although their deflections were 2.5% larger than that of the honeycomb cores. Therefore, the pyramidal truss cores could replace the aluminum honeycomb cores, and their multi-functional capability could be exploited.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.10
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• pp.80-87
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• 2006

Metallic sandwich plate with a truss core has metallic inner structures which have low relative density between a pair of metal skin sheets or face sheets. In this work, low impact tests have been carried out to examine the behavior of sandwich plates with a pyramidal truss core. For the low velocity impact, the impact apparatus of drop weight type has been fabricated. From the results of the experiments, maximum energy absorption is found to happen when the upper sheet fails. The sandwich plate loses its absorption ability as soon as the inner structures have been crashed completely and optimal core thickness has existed to maximize energy absorption. Comparing the metallic sandwich plate with the monocoque plate, the absorbed energy has been improved up to 160 % and the deflection decreased by up to 76%. As a result, the metallic sandwich plate with a truss core is shown to have good material for impact resistance and energy absorption.