• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1999.10a
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• pp.20-20
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• 1999

고대로부터 이용되어온 풍력에너지는 특히 풍황이 양호한 서유럽을 중심으로 꾸준히 개발되어 왔다. 최근 세계 여러 나라에서는 화석에너지의 고갈과 심각한 환경오염 문제 등으로 인하여 청정에너지의 개발에 많은 투자를 하고있으며 이에 따라 우리 나라에서도 풍력발전기의 개발이 진행되고 있다. 풍력에너지의 효율적인 이용을 위해서 여러 가지 형태의 발전시스템이 시도되어 왔으나 최근에는 성능 및 효율성이 우수하고 일정 출력을 낼 수 있도록 깃 각 조정이 가능한 수평축 풍력발전시스템이 주로 사용되고 있으며 대형화함으로서 대두되는 경량화 문제를 해결하기 위해 복합재를 이용한 회전날개를 개발하여 이를 사용하고 있다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2000.11a
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• pp.26-26
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• 2000

본 연구에서는 풍력발전기용 복합재 회전날개의 설계단계에서 공력 설계 후 결정되어진 공력 형상을 기초로 하여 구조적 형상설계를 수행 할 때에 여러 가지 경우의 형상을 해석하여 이중 설계요구조건에 적합한 경우를 채택하는 시행착오 방법으로 인한 비효율적인 요소를 배재 하기 위해 고전 적층판 이론을 기초로 한 해석 프로그램을 사용하여 예비설계를 수행하는 수정된 설계절차를 제안하였으며 예비설계단계에서 신속하고 신뢰성 있는 해석결과를 얻을 수 있었다.(중략)

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2000.04a
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• pp.38-38
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• 2000

풍력 발전용 회전 날개는 대형화되면서 종래의 목재나 금속재료로는 구조적 강도, 강성 및 피로수명, 경제성 등을 만족하지 못하게 되었고, 이를 보완하기 위해 복합재료의 사용이 불가피하게 되었다. 따라서 본 연구에서는 국내업체에서 생산하여 그 물성이 입증된 E-glass/Epoxy 복합재료를 사용하여 국내 기상조건에 적합한 풍력발전용 회전날개를 개발하였다. 그러나, 개발된 회전날개는 국내 기상조건에 적합하도록 설계된 것으로서 해외로 수출할 경우 국내보다 풍속이 큰 지역에서는 구조적 안정성 및 피로수명을 만족할 수 없게 된다. 즉, 개발된 회전날개의 외국시장 진출을 위해서는 국제규격에 따른 하중의 정의와 구조설계의 개선이 필요하다. 따라서 본 연구에서는 IEC 1400-1의 국제규격을 검토하여 이를 만족하도록 회전날개의 구조설계를 수행하였다. 그 결과 국제규격에 명시된 강도 및 피로수명을 만족하는 구조설계 결과를 얻을 수 있었다.

• Composites Research
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• v.29 no.2
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• pp.53-59
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• 2016

Aircraft wing structure is used as a fuel tank containing the fluid. Fuel tank and joint parts are consists of composite structure. Hydrodynamic Ram(HRAM) effect occurs when the high speed object pass through the aircraft wing or explosion and the high pressure are generated in the fuel tank by HRAM effect. High pressure can cause failure of the fuel tank and the joint parts as well as the aircraft wing structure. To ensure the aircraft survivability design, we shall examine the behavior of the joint parts in HRAM effect. In this study, static tensile tests were conducted on four kind of the composite T-Joints. The failure behavior of the composite T-joint was examined by strain gauges and high speed camera. We examine the validity of the Finite Element Modeling by comparing the results of FEA and static tensile tests. The failure stresses and failure pressure of the composite T-Joint were calculated by FEA.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.10
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• pp.928-935
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• 2015

This paper presents low temperature structural tests of a UAV wing which has room temperature-curing adhesive bond. The wing structure is made of carbon fiber reinforced composites, and the skins are bonded to the inner structures (such as ribs and spars) using room temperature-curing adhesive bond. Also, to verify damage tolerance design of the wing structure, barely visible impact damages are intentionally created in the critical areas. The attachment fittings of the wing are fixed in a specially designed chamber which can simulate the low temperature environments of the operating altitudes. The test load is applied by hydraulic actuators which are placed outside the chamber. The structural tests consist of strain survey tests and a durability test for 1-life fatigue load spectrum. During the tests, strains of major parts are measured by strain gauges and FBG sensors. The change of the initial impact damages is also monitored using piezoelectric sensors. The 1-life damage tolerance of the composite structure is verified by the structural tests under the simulated environments.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.7
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• pp.535-540
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• 2019

The coupling between different models for MDO (Multi-disciplinary Optimization) greatly increases the complexity of the computational framework, while at the same time increasing CPU time and memory usage. To overcome these difficulties, POD (Proper Orthogonal Decomposition) and RBF (Radial Basis Function) are used to solve the optimization problem of determining the thickness of composites and sandwich cores when composite sandwich structures are used as aircraft wing skin materials. POD and RBF are used to construct surrogate models for the wing shape and the load data. Optimization is performed using the objective function and constraint function values which are obtained from the surrogate models.

• Journal of the Korean Society of Propulsion Engineers
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• v.2 no.3
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• pp.1-9
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• 1998

The exhaustion of fossil fuels and serious environmental pollution put the concern about non-po llution energy into the world. On the developments of technology, wind energy has been spotlighted as a non-pollution energy in many countries. This study has carried out the aerodynamic and structural design procedure of the lightweight composite rotor blades with an appropriate aerodynamic performance and structural strength for the 500㎾ medium class wind turbine system. The previous design, which is shell-spar structure, is redesigned to shell-spar- sandwich structure for light weight. Large deformation problem from light weight is examined by non-linear analysis. Local buckling occurred under lower stress than failure stress. The buckling analysis is accomplished to confirm the safety of the composite blade. The stress analysis around pin hole joint part at hub is carried out and it is confirmed that the pin hole is not failed. The results show that the resonance of redesigned blade does not happen in operation range.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.2
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• pp.24-30
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• 2004

• Composites Research
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• v.32 no.1
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• pp.45-49
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• 2019

Fiber reinforced composites fabricated by the resin film infusion (RFI) process, which is one of the outof-autoclave process, have the advantage of significantly reducing the processing cost in large structures while having excellent mechanical properties and uniform impregnation of the resin. In this study, we applied RFI carbon fiber composites to unmanned aerial vehicle structures to improve structural safety and achieve weight reduction. The tensile test results showed that the strength was 46% higher than that of generic T300 grade plain weave carbon fiber composites. As a result of the layup design and finite element analysis of the composite wing structure using the above material properties, the wing tip deflection is decreased by 31%, the structural safety factor is increased by 28% and the weight of the entire structure can be reduced by more than 10% compared to the reference model using glass fiber composite material.

• Journal of the Korean Society of Propulsion Engineers
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• v.4 no.1
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• pp.22-29
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• 2000

In this study, the 750㎾ scale composite blade for the horizontal axis wind turbine system was designed and manufactured, and it was tested and evaluated by the specific structural test rig. In the test, it was found that local bucklings at the trailing edge of the blade and excessive deflections at the blade tip were happened. In order to solve these problems, the design of blade structure was modified. after improving the design, the abrupt change of deflection at the blade tip was reduced by smooth variation of the spar thickness and the local buckling was removed by extending the web length. The modified design was analyzed by the FEM, the safety and stability of th blade structure.