• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.4
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• pp.336-343
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• 2014

Modern advanced-turboprop propellers are required to have high structural strength to cope with the thrust requirement at high speed. The high stiffness and strength carbon/epoxy composite material is used for the major structure and skin-spar-foam sandwich structural type is adopted for advantage in terms of the blade weight. As a design procedure for the present study, the structural design load is estimated through investigation on aerodynamic load and then flanges of spars from major bending loads and the skin from shear loads are sized using the netting rule and Rule of Mixture. In order to investigate the structural safety and stability, stress analysis is performed by finite element analysis code MSC. NASTRAN. It is found that current methodology of composite structure design is a valid method through the static structural test of prototype blade.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.2073-2079
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• 2008

This study aims to investigate the residual strength of sandwich composites with Al honeycomb core and carbon fiber face sheets after the quasi-static indentation damage by the experimental investigation. The 3-point bending test and the edge-wise compressive strength test were used to find the mechanical properties. The quasi-static point load and damaged hole was applied to introduce the simulated damage on the Each damaged specimens were finally assessed by the 3-point bending test and the compressive strength test. The investigation results revealed the residual strength of the damaged specimens due to the quasi-static indentation.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.2
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• pp.149-156
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• 2007

The present study provides structural design and analysis of main wing and horizontal tail of a small scale WIG(Wing in Ground Effect) vehicle which has been developed as a part of the high speed maritime transportation system for the future of Korea. Weight saving as well as structural stability could be achieved by skin-spar with foam sandwich design and with wide application of carbon/epoxy composite material. A commercial FEM code, NASTRAN, was utilized to confirm the structural safety and stability through sequential design modifications to meet the final design goal. In addition, each wing and the fuselage were fastened together by eight insert bolts with high strength to accomodate easy assembling and disassembling as well as to guarantee a service life longer than 20 years.

• Composites Research
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• v.22 no.1
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• pp.22-31
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• 2009

Recently the wind energy has been alternatively used as a renewable energy resource instead of the mostly used fossil fuel due to its lack and environmental issues. This work is to propose a structural design and analysis procedure for development of the 500W class small wind turbine system which will be applicable to relatively low speed region like Korea and for the domestic use. The wind turbine blade was performed structural analysis including stress, deformation, buckling, vibration and fatigue. In addition, the blade should be safe from the impact damage due to FOD(Foreign Object Damage) including the bird strike. MSC.Dytran was used in order to analyze the bird strike penomena on the blade, and the applied method Arbitrary Lagrangian-Eulerian was evaluated by comparison with the previous study results. Finally, the structural test was carried out and its test results were compared with the estimated results for evaluation of the designed structure.

• Journal of the Korea Institute of Building Construction
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• v.9 no.4
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• pp.63-73
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• 2009

Recently, the use of lightweight panels in building structures has been increasing. Of the various lightweight panel types, styrofoam sandwich panels are inexpensive and are excellent in terms of their insulation capacity and their constructability. However, sandwich panels that include organic material are quite vulnerable to fire, and thus can numerous casualties in the event of a fire due to the lack of time to vacate and their emission of poisonous gas. On the other hand, lightweight foamed concrete is excellent, both in terms of its insulation ability and its fire resistance, due to its Inner pores. The properties of lightweight concrete is influenced by foaming agent type. Accordingly, this study investigates the insulation properties by foaming agent type, to evaluate the possibility of using light-weight foamed concrete instead of styrene foam. Our research found thatnon-heating zone temperature of lightweight foamed concrete using AP (Aluminum Powder) and FP (animal protein foaming agent) are lower than that of light-weight foamed concrete using AES (alkyl ether lactic acid ester). Lightweight foamed concrete using AES and FP satisfied fire performance requirements of two hours at a foam ratio 50, 100. Lightweight foamed concrete using AP satisfied fire performance requirements of two hours at AP ratio 0.1, 0.15. The insulation properties were better in closed pore foamed concrete by made AP, FP than with open pore foamed concrete made using AES.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2012.03a
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• pp.56-56
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• 2012

본 연구는 가정용 및 산업용 유해가스제거용 필터여재의 제조에 관한 것으로 핫멜트(hot-melt) 분사 시스템에 의한 다층구조의 부직포와 활성탄 등의 흡착물질로 구성되는 샌드위치 복합시트 및 필터여 재의 제조에 사용되는 구성재료의 최적화에 관한 연구이다. 스프레이 본딩 시스템에 의한 공정은 종래의 유해가스제거용 필터 미디어의 제조하는 방법인 활성탄과 바인더 역할을 하는 핫멜트 수지를 혼합하여 부직포 원단에 도포하여 활성탄을 부착시키는 공정에 비해 도포되는 핫멜트 수지의 양이 감소에 의한 생산비절감과 충분한 활성탄 도포에 의한 기능성 향상 등에 의해 유해가스 포집율을 높일 수 있으며 공정 이후 스프레이에 의해 도포된 핫멜트수지의 자연건조 방식에 의한, 열원이 불필요하며, 에너지가 절감되며, 속도 향상에 의한 생산성 향상, 분진발생 최소화로 인한 제조현장의 환경개선이 가능할 것으로 사료된다. 1차적으로 본 연구의 필터제조의 최적화를 위해서 스프레이 본딩시스템에 효율적으로 사용가능한 다양한 수지를 검토하였으며, 기존 외산 캐빈필터여재의 미세구조 및 성능특성, 다양한 활성탄의 흡착성능검토, 사용 가능한 여재의 특성분석을 통해 다층구조의 필터 여재에 사용 가능한 구성재료의 최적화에 중심을 두었다.

• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.4
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• pp.422-428
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• 2018

Increase in use of lightweight structures, coupled with the increased acoustic loads resulting from larger and longer range guided missiles, has made missile more susceptible to failures caused by acoustic loads. Thus, accurate prediction of acoustic environment and the response is becoming ever more important for mission success. In this paper, the acoustic response of a sandwich composite skin structure to diffuse acoustic excitation is predicted over a broad frequency range. For the low frequency acoustic analysis, coupled FE-BEM method is used where the structure is modeled using FEM and the interior and exterior fluid is modeled using BEM. For the high frequency region, statistical energy analysis is applied. The predicted acoustic level inside the structure is compared with the result from acoustic test conducted in reverberation chamber, which shows very good agreement.

• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.3
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• pp.288-294
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• 2018

Recently, as the speed and performance of the launcher and the missile have been improved, it is necessary to consider the acoustic load of launching and flight in initial design step. In this paper, an experimental study on acoustic absorption and transmission characteristics of aluminium vs. sandwich composite structures were conducted. The overall noise reduction was evaluated by performing an acoustic test in the reverberation room, and the acoustic absorption and transmission loss of the structures were analyzed by conducting the sound absorption test inside the structure.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.3
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• pp.235-241
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• 2016

Underwater weapon system is required to structurally strong material, since as it is directly exposed to external shock. It should also be using the lightweight material in order to take advantage of buoyancy. Composite materials meet these requirements simultaneously. Particularly in the case of submarine, composite materials are widely used. It is important to have a high strength enough to be able to withstand external shock, but it is also important to attenuate it. In a method for the shock damping, viscoelastic damping materials are inserted between the high strength composite material as a sandwich structure. Shock attenuation can be evaluated in the loss factor. In ASTM(American Society of Testing Materials), evaluation method of the loss factor of cantilever specimens is specified. In this paper, mode tests of the cantilever are performed by the ASTM standard, in order to calculate the loss factor of the viscoelastic damping material by the specified expression. Further, for verifying of the calculated loss factor, mode test of compound beams is carried out. In addition, the characteristics of the material were analyzed the effect on the loss factor.

• 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.