• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.8
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• pp.56-64
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• 2002

In this work, a smart skin of multi-layer structure is designed and manufactured. Through the compression test, the characteristic of smart skin behavior was examined. We have predicted stress of each layer and the first failed layer of the smart skin structure by using MSC/NASTRAN. The finite element model was verified by comparing measured data from the compression test and result from the geometrically linear/non-linear analysis. The finite element model was used for obtaining design data from the parametric study. It was confirmed that shear moduli of honeycomb core affect the buckling load of smart skin where shear deformation was considerable.

• Transactions of Materials Processing
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• v.15 no.4 s.85
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• pp.326-332
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• 2006

Sandwich structures, which are composed of a thick core between two faces, are commonly used in many engineering applications because they combine high stiffness and strength with low weight. Depending on the sheets by a rolling process, which is a more efficient and economical approach compared to other types of processes, has become an increasingly important subject of study. In this paper, we made a roll forming machine which progressive forming possible and force measurement for a roll forming of the sheet metal forming. And we designed a roll molding that arrayed of embossing size 3mm in diameter fabricate micro dimple inner structure plate. We carried out forming experiment such as array change and thickness to sts304 sheet. Ultimately, this research developed inner structure plate of high stiffness.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.447-448
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• 2009

On this study, the concrete foaming was maximized using Hydrogen peroxide($H_2O_2$) reciprocal decomposition catalyzed by Manganese dioxide($MnO_2$) and Sodium bicarbonate($NaHCO_3$). Also, we study the physical and mechanical properties of lightweight formed concrete through diverse experiment which is to determine the optimal mixing proportion and require strength of the lightweight formed concrete. As a result of an experiment, it is satisefied with overall quality standard on the KS F 4039 and KS F 2459 provision.

• Journal of the Korean Society of Industry Convergence
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• v.19 no.3
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• pp.109-124
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• 2016

The objective of this paper is to find the density, stiffness, and strength of truss-wall diamond corrugation model combined with pinwheel truss inside space. The truss-wall diamond corrugation (TDC) model is defined as a unit cell coming from solid-wall diamond corrugation (SDC) model. Pinwheel truss-wall diamond corrugation (P-TDC) model is made by TDC connected with pinwheel structure inside of the space. Derived ideal solutions of P-TDC is based on truss-wall and pinwheel truss model at first. And then it is compared with Gibson-Ashby's ideal solution. To validate the ideal solutions of the P-TDC, ABAQUS software is used to predict the density, strength, and stiffness, and then each of them are compared to the ideal solution of Gibson-Ashby with a log-log scale. Applied material property is stainless steel 304 because of having cost effectiveness. Applied parameters for P-TDC are 1 thru 5 mm diameter within fixed opening width as 4mm. In conclusion, the relative Young's modulus and relative yield strength of the P-TDC unit model is reasonable matched to the ideal expectations of the Gibson-Ashby's theory. In nearby future, P-TDC model is hoped to be applied to make sandwich core structure by advanced technologies such as 3D printing skills.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.11 s.242
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• pp.1551-1559
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• 2005

This paper explains manufacturing process and experimental studies on a composite carbody of Korean tilting train. The composite carbody with length of 23m was manufactured as a sandwich structure composed of a 40mm-thick aluminium honeycomb core and 5mm-thick woven fabric carbon/epoxy face. In order to evaluate structural behavior and safety of the composite carbody, the static load tests such as vertical load, end compressive load, torsional load and 3-point support load tests have been conducted. These tests were performed under Japanese Industrial Standard (JIS) 17105 standard. From the tests, maximum deflection was 12.3mm and equivalent bending stiffness of the carbody was 0.81$\times$10$^{14}$ kgf$\cdot$mm$^{2}$ Maximum stress of the composite body was lower than 12.2$\%$ of strength of the carbon/epoxy. Therefore, the composite body satisfied the Japanese Industrial Standard.

• Journal of the Korean Society for Advanced Composite Structures
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• v.2 no.3
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• pp.12-17
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• 2011

This paper presents the flexural behavior of a hybrid Glass Fiber-Reinforced Polymer(GFRP)-steel decks for use in deteriorated bridge decks replacement. Static load tests were conducted to investigate the structural characteristics of the hybrid FRP-steel deck. The tested deck panel satisfied the design criteria. The failure mode of the hybrid deck was demonstrated ductility with deformation beyond initial yielding. The responses were compared with the ANSYS finite element predictions. It was found that the presented hybrid deck was efficient for use in bridges. The thickness of the hybrid deck may be decreased when compared to that of the all FRP deck with similar flexural rigidity.

• Journal of the Korean Society for Railway
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• v.10 no.1 s.38
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• pp.39-44
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• 2007

This rafer explains a durability test of a large train car body made of carbon/epoxy composite material. The composite car body with the length of 23m was manufactured as a sandwich structure composed of an aluminum honeycomb core and CF1263 woven fabric carbon/epoxy faces. In order to evaluate durability of the composite car body, it was excited by two 500kN capacity hydraulic actuators installed underneath the body bolster. The natural frequency of the composite car body under full weight condition was found to be 4.33Hz. Based on this result, the excitation frequency and displacement of 5Hz and ${\pm}1.0mm$, respectively, were used as inputs for the durability test. The test was conducted for $2{\times}10^6$ cycles. During the test, the nondestructive tests using X-ray radiography and dye penetration method was performed to determine the presence of the cracks. Upon completion of the test, no cracks were found.

• Composites Research
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• v.22 no.3
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• pp.55-59
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• 2009

Microstrip antennas are low profile, are conformable to planar and nonplanar surfaces, are simple and inexpensive to manufacture, mechanically robust when mounted on rigid surfaces and are compatible with MMIC(Monolithic microwave integrated circuit) designs; they have been used in diverse communication systems. The rectangular microstrip patch antenna is designed for a central frequency of 12.5 GHz, and the final product is a $4{\times}1$ array antenna with curvature radius of 200 mm. The microstrip antenna is embedded in a sandwich structure which consists of skin and core material. After impact, the performance of damaged antenna is estimated by measuring the return loss and radiation pattern. The antenna performance was not affected by this impact damage.

• 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.

• Composites Research
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• v.37 no.3
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• pp.219-225
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• 2024

It is essential to develop a light-weight, high-performance structure for the deployable reflector antenna, which is the payload of a reconnaissance satellite, considering launch and orbital operation performance. Among them, the composite main reflector is a key component that constitutes a deployable reflector antenna. In particular, the development of a high-performance main reflector is required to acquire high-quality satellite images after agile attitude control maneuvers during satellite missions. To develop main reflector, the initial design of the main reflector was confirmed considering the structural performance according to the laminate stacking design and material properties of the composite main reflector that constitutes the deployable reflector antenna. Based on the initial design, four types of composite main reflectors were manufactured with the variable for manufacturing process. As variables for manufacturing process, the curing process of the composite structure, the application of adhesive film between the carbon fiber composite sheet and the honeycomb core, and the venting path inside the sandwich composite were selected. After manufacture main reflector, weight measurement, non-destructive testing(NDT), surface error measurement, and modal test were performed on the four types of main reflectors produced. By selecting a manufacturing process that does not apply adhesive film and includes venting path, for a composite main reflector with light weight and structural performance, we developed and verified a main reflector that can be applied to the SAR(Synthetic Aperture Rader) satellite.