• Journal of the Korean Society for Precision Engineering
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• v.27 no.3
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• pp.111-117
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• 2010

The repeated unit cell structure is applied to the composite, the carbon nano tube and sandwich panel. In this paper, a study on the stiffness of unit cell structure has been performed with the tube support plate of the steam generator. For this, repeated unit cell structure's equivalent elastic constant and poisson's ratio was evaluated through FEA and tests under the elastic range load. Also we evaluated the effect on the specimen size from results.

• Journal of Aerospace System Engineering
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• v.15 no.4
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• pp.30-39
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• 2021

This paper presents a study on the design and structural substantiation of the interior structure of the new VVIP aircraft. In this study, the structural design and analysis of the compartment with aluminum alloy and sandwich composite panel were performed. The structural design requirements from the Federal Aviation Administration were identified. The structural analysis of the compartment was performed by the utilization of the finite element analysis method, for the structural design process. Therefore, the designed cabin compartment secured the structural integrity, and satisfied its certification standards and design requirements via structural analysis.

• Composites Research
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• v.12 no.6
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• pp.74-82
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• 1999

The static and fatigue characteristics of polyurethane foam cored sandwich structures are investigated. Three types of the specimens with the glass fabric faces and the polyurethane foam core are used; non-stitched. stitched, and stiffened sandwich specimen. Especially additional structural reinforcements with the twisted polyester and glass fiber for thickness direction are made to stitched sandwich structure panel to minimize the delamination of structure which is stitched the upper and lower faces through the core and the resin is impregnated Into stitched fiber with the characteristics of low viscosity of resin at resin flow temperature and cured together with during the curing process. Bending strength of stitched specimen which is 50 mm $50{\times}50{\;}mm$ pitched is improved by 50 % as com-pared with non-stitched specimen and stiffened specimen is improved 10 times more than non-stitched structure. After fatigue testing of $10^6$cycles by 20% of ultimate load under monotonic load, the bending fatigue strength of non-stitched specimen is decreased by 27% of monotonic bending strength, 39% for stitched structure and 20% for stiffened specimen. To verify the aging effect of polyurethane form core, Ultrasonic C-scanning equipment is used to detect the damage of skin laminate alone after fatigue test. From results of UT C-scan images, there is no defect that can be damaged occurred during fatigue test. It is concluded that the decrease of bending strength for foam cored sandwich specimen is caused by the decrease of stiffness due to the aging of polyurethane foam core during fatigue cycles.

• Fire Science and Engineering
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• v.31 no.6
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• pp.33-39
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• 2017

Composite panel refers to the particular plywood produced in a way of stacking the different kinds of material in sandwich form and adhering them using adhesives and is widely used as building material for its constructability and cost efficiency. But as the surface is finished with steel plate, fire extinguishing agent cannot reach to the core material because of such steel plate on surface which causes the difficulties in suppressing the fire as well as in fire-fighting activities due to collapse. This study, to deal with such problem, is intended to set the fire pipe in core material to prevent the fire from spreading and in a bid to achieve this using minimized fire water, water supply test device was fabricated to estimate the required water flow of fire extinguisher and consequently, optimal water flow (0.5 L/min) was determined through a full-scale fire test.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.10
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• pp.418-423
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• 2018

Recently, research and development of high-value leisure vessels has been carried out in Korea to revitalize the marine leisure industry and tap into the global maritime leisure market. FRP composite materials, which have excellent physical properties and are available for the manufacture of light hulls, are used widely. One of the most important design technologies is to secure structural safety of leisure vessels made from FRP composite materials. In this study, the structural strength was assessed for the design of an 8-meter high-speed planing leisure boat made from FRP composite materials. The design loads to verify the structural safety were calculated according to the rules for the classification of high speed light craft (KR, 2015), and structural analysis was conducted using a finite element model composed of an isotropic shell element, which has equivalent bending rigidity with the FRP sandwich panel. The analysis results were compared with the results of the strength test for fabricated specimens, and all internal structural components are sufficiently satisfied with the structural strength.

• Composites Research
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• v.30 no.6
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• pp.356-364
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• 2017

Composite lattice structures are tried to be used in various fields because of its benefit in physical properties. With increase of demand of the composite lattice structure, nondestructive testing technology is also required to certificate the quality of the manufactured structures. Recently, research on the development of the composite lattice structure in Republic of Korea was started and accordingly, fast and accurate non-destructive evaluation technology was needed to finalize the manufacturing process. This paper studied non-destructive testing methods for composite lattice structure using laser ultrasonic propagation imaging systems. Pulse-echo ultrasonic propagation imaging system was able to inspect a rib structure wrapped with a skin structure. To reduce the time of inspection, a band divider, which can get signal in different frequency bands at once, was developed. Its performance was proved in an aluminum sandwich panel. In addition, to increase a quality of results, curvature compensating algorithm was developed. On the other hand, guided wave ultrasonic propagation imaging system was applied to inspect delamination in a rib structure. To increase an area of inspection, multi-source ultrasonic wave propagation image was applied, and defects were successfully highlighted with variable time window amplitude mapping algorithm. These imply that ultrasonic propagation imaging systems provides fast and accurate non-destructive testing results for composite lattice structure in a stage of the manufacturing process.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.9
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• pp.1099-1107
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• 2013

This study proposes a weight reduction design for urban transit, specifically, a Korean EMU carbody made of aluminum extrusion profiles, according to size optimization and useful material changes. First, the thickness of the under-frame, side-panels, and end-panels were optimized by the size optimization process, and then, the weight of the Korean EMU carbody could be reduced to approximately 14.8%. Second, the under-frame of the optimized carbody was substituted with a frame-type structure made of SMA 570, and then, the weight of the hybrid-type carbody was 3.8% lighter than that of the initial K-EMU. Finally, the under-frame and the roof-panel were substituted with a composite material sandwich to obtain an ultralight hybrid-type carbody. The weight of the ultralight hybrid-type carbody was 30% lighter than that of the initial K-EMU. All the resulting carbody models satisfied the design regulations of the domestic Performance Test Standard for Electrical Multiple Unit.

• Journal of the Korea Concrete Institute
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• v.26 no.4
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• pp.421-428
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• 2014

This paper describes the experimental results of insulated concrete sandwich wall panels (CSWP) with corrugated glass fiber-reinforced polymer (GFRP) shear connectors under in-plane shear loading. Corrugated GFRP shear connectors were used to improve the thermal property of insulated CSWP and to achieve composite action between the interior and exterior concrete wall panels. Test specimens were consist of three concrete panels with two insulation layers between concrete panels and middle concrete panels was loaded in the direction of gravity. To evaluate the effects of insulation types (extruded polystyrene, XPSS and expanded polystyrene, EPS), shear connector pitch (300 and 400 mm) and width (10 and 15 mm) on in-plane shear behavior of insulted CSWP, failure mode and shear flow-average relative slip relationship of specimens were investigated. Test results indicate that the bond stress between concrete panel and insulation is considerable initially. Especially in case of insulated CSWP without shear connector, initial stiffness of CSWP with XPSS is superior to that of CSWP with EPS. The shear connector's contribution to in-plane shear performance of insulated CSWP depends on the type of insulation.

• Journal of Life Science
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• v.26 no.6
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• pp.633-639
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• 2016

Biomaterials including polymer, metal, ceramic, and composite have been widely applied for medical uses as medical fibers, artificial blood vessels, artificial joints, implants, soft tissue, and plastic surgery materials owing to their physicochemical properties. However, the biocompatibility and toxicity for film- and plate-form biomaterials is difficult to measure in mammalian cells because there is no appropriate incubation system. To solve these problems, we developed a novel mammalian cell culture system consisting of a silicone ring, top panel, and bottom panel and we applied two polymer films (PF) and one metal plate (MP). This system was based on the principal of sandwiching a test sample between the top panel and the bottom panel. Following the assembly of the culture system, SK-MEL-2 cells were seeded onto Styela Clava Tunic (SCT)-PF, NaHCO₃-added SCT (SCTN)-PF, and magnesium MP (MMP) and incubated at 37℃ for 24 hr and 48 hr. An MTT assay revealed that cell viability was maintained at a normal level in the SCT-PF culture group at 24 or 48 hr, although it rapidly decreased in the SCTN-PF culture group at 48 hr. Furthermore, the cell viability in the MMP culture group was very similar to that of the control group after incubation for 24 hr and 48 hr. Together, these results suggest the sandwich-type mammalian culture system developed here has the potential for the evaluation of the biocompatibility and toxicity of cells against PF- and MP-form biomaterials.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.10
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• pp.841-847
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• 2021

In this paper, the applicability of the low-density surface film copper mesh for aircraft applications have been analyzed. Recently, low-density surface film copper mesh is developed to reduce weight and cost compared with traditional surface film copper mesh. In order to apply low-density surface film copper mesh to aircraft, it is needed to analyze its electromagnetic effects as well as structural integrity with sandwich panels to prevent pinholes. The structural integrity and electromagnetic characteristics have been analyzed for 2 samples of low-density surface film copper mesh and 1 sample of surface film copper mesh. To review the applicability of the low-density surface film, it is combined with sandwich composite panel to confirm pinhole effects. The low-density surface film has been modeled as a periodic structure and analyzed with 3D electromagnetic simulation tool. The simulation results has been verified through measured electromagnetic transmission results using free space measurements. From the results, it will be possible to use these results for the analysis and the applicability of low-density surface film copper mesh for aircraft.