• 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 Advanced Marine Engineering and Technology
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• v.26 no.2
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• pp.165-173
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• 2002

복합재부품의 제작후 검사로 적용될수 있는 방법은 방사선 투과검사와 초음파검사가 있으며, 전자는 특정 검사시에 국한되어 사용되며 그외의 검사에는 후자가 적용되는 것이 일반적이다. 복합재부품의 검사를 원활하게 수행하기 위해서는 초음파검사의 기본이론과 적용가능한 기법에 대한 이해가 필수적이다. 따라서 아래에서 초음파검사의 기본원리에 대해 간략하게 설명하고 그 실제 제작되고 있는 복합재부품에 대한 검사예를 살펴보고자 한다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.8
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• pp.780-788
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• 2009

AE technique was applied to the static structural test of the composite wing structure to evaluate the structural integrity and damage. During the test, strain and displacements measurement technique were used to figure out for static structural strength. AE parameter analysis and source location technique were used to evaluate the internal damage and find out damage source location. Design limit load test, the 1st and 2nd design ultimate load tests and fracture test were performed. Main AE source was detected by an sensor attached on skin near by front lug. Especially, at the 1st design ultimate test, strain and displacements results didn't show internal damage but AE signal presented a phenomenon that the internal damage was formed. At the fracture test, AE activities were very lively, and strain and displacements results showed a tendency that the load path was changed by severe damage. The internal damage initiation load and location were accurately evaluated during the static structural test using AE technique. It is certified from this paper that AE technique is useful technique for evaluation of internal damage at static structural strength test.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.1
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• pp.22-28
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• 2010

To detect the damage in composite structure, nondestructive evaluation techniques are widely used. Tapping test is perhaps the most common technique used for the detection of damage in composite laminates. The method is accomplished by tapping the inspection area with light hammer-like device. The tapping test has the ability that indicates damages in a structure due to a localized change of stiffness. The change in vibration signature may be detected by measurement of the dynamic contact force during impact. In this study, it has been shown that the characteristics of impact force histories from a structure during tapping are changed by the presence of damage such as surface crack and delamination. And impact response analysis has been performed on composite rotor blade with crack to investigate the effect of damage.

• Composites Research
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• v.34 no.5
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• pp.296-304
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• 2021

This study presented the evaluation of the stamp forming process for L-shape CF/PEKK thermoplastic composite using the finite element model. The formability of three different trimming allowances has been examined for representative product geometry. The results showed that those manufactured by high trimming allowance showed more excellent formability in those areas. Moreover, the effects of the trimming allowances on the stress, thickness, wrinkle distributions of thermoplastic composites fabricated with the stamp forming process were evaluated. The comparison of the simulation and experimental results for the thickness and wrinkle distributions proved the accuracy of the stamp forming model. The crystallinity of the composite was performed by differential scanning calorimetry (DSC). The void content of the composite was evaluated by matrix digestion. Then, the fabricated structure was characterized and achieved high quality in crystallinity and void content. Consequently, the presented FEM modeling shows excellent potential for application in the aircraft product design process. This pragmatic approach could efficiently offer a valuable solution for the thermoplastic composite manufacturing field.

• Journal of Aerospace System Engineering
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• v.11 no.4
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• pp.1-7
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• 2017

The development of effective design allowable values for unmanned composite aircraft is an issue of paramount concern for the industry. The application of conventional manned aircraft structural certification methods to unmanned aircraft such as prototype and technology demonstrators, can lead to excessively long development time and costs. In this paper, the determining method of composite structure design allowable values for light composite unmanned aircraft is presented to reduce to the structural weight. This paper seeks to show the applicability of composite B-basis material values as a design allowable of light composite unmanned aircraft structures. A review of different civil and UAV targets failure probability is given. From the results, the researchers can know that the requirements of light composite unmanned aircraft design allowable should be alleviated, compared to manned composite aircrafts.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.95.2-95.2
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• 2012

고온형 SOFC의 개발에 있어 스택의 신뢰성을 확보하는데 가장 중요한 핵심기술은 스택 구성요소 사이를 접합하는데 필요한 고온형 밀봉재의 개발이다. SOFC 스택에서의 밀봉재는 고체전해질과 접속자 사이에서 음극에 공급되는 연료가스와 양극에 공급되는 공기가 서로 혼합되는 것을 방지하는 역할은 물론 기계적으로 취약한 단전지의 보호 및 스택전체 구조물의 구조적 일체성(Structural integrity)을 부여하는데 주목적이 있다. 현재 기체 기밀성을 유지하기 위한 밀봉재는 크게 유리 및 결정화 유리계, mica및 mica/유리복합재료, 유리/충전재 복합재료 등이 사용되고 있으나 다수의 단위전지로 구성되는 스택 구성에서 스택의 열기계적 안정성 및 장기수명을 보장하기 위해서는 본 연구에서 개발하고자 하는 복합밀봉재가 가장 적합할 것으로 예상되고 있다. 본 연구에서는 SiO-B2O3-RO계에 BaO, SrO를 일정비율로 첨가하여 제작된 유리 frit을 열처리하여 물리화학적 물성변화를 검토하였으며, $750^{\circ}C$ 이하의 연화점을 갖는 유리를 기지상으로 하고 세라믹 보강재를 첨가한 고온형 복합밀봉재를 개발하고 그 물리화학적 안정성, 열기계적 안정성 및 밀봉 특성을 평가하였다.

• Composites Research
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• v.24 no.5
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• pp.9-16
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• 2011

This paper describes the crashworthiness evaluation and performance improvement of tilting train made of sandwich composites. The applied sandwich composite of carbody structure was composed of aluminum honeycomb core and glass/epoxy & carbon/epoxy laminate composite facesheet. Crashworthiness analysis of tilting train was carried out using explicit finite element analysis code LS-DYNA 3D. The 3D finite element model and 1D equivalent model were applied to save the finite element modeling and calculation time for crash analysis. The crash conditions of tilting train were conducted according to four crash scenarios of the Korean railway safety law. It found that the crashworthiness analysis results were satisfied with the performance requirements except the crash scenario-2. In order to meet the crashworthiness requirements for crash scenario-2, the stiffness reinforcement for the laminate composite cover and metal frames of cabmask structure was proposed. Consequentially, it has satisfied the requirement for crash scenario-2.

• The Journal of Aerospace Industry
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• s.65
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• pp.70-88
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• 2003

필자가 참여했던 쌍발복합재사업, 쌍발복합재항공기사업, SB427 민수용헬기사업, T-50 초음속고등훈력기 사업을 통해 복합재료의 항공기 적용사례를 고찰하면서, 쌍발복합재항공기는 실험용항공기(Experimental Aircraft)이지만 국내 최초의 전복합재항공기(All-composites Aircraft)로서 항공기 구조물이 순전히 복합재료만을 이용하여 설계 및 제작이 가능하다는 것을 보여주었고, 복합재료를 적용 시 어떠한 이점이 있는지를 보여준 예가 되고 있다. SB427 민수용헬기사업은 헬리콥터에서 로터 블레이드와 동체 등 기체구조물 대분에 왜 복합재료를 사용해야 효과적인 지를 잘 보여주고 있다. SB427 개발 사업을 통해 얻을 수 있는 또 다른 점은 민수용 항공기의 경우 구축된 복합재료 인증체계에 따라 복합재구조물을 개발해야 되고 그래야만 마케팅에서 신뢰를 얻을 수 있다는 것이다. T-50 항공기는 국내에서 최초로 개발된 초음속기로 미익 부문에 복합재료가 응용되었다. 양산 항공기의 주구조물에 복합재료가 쓰인 예는 T-50이 첫 번째 인데 T-50에서 얻어진 복합재 적용기술은 앞으로 개발될 고급 군용기와 민수용기에 널리 활용될 것으로 기대된다. 본 논문에서는, 국내 개발 항공기에서의 복합재료 적용이라는 특정 주제를 중심으로 개발 이력과 기술적 조망을 통하여, 정부, 연구소, 업체 간의 유기적이고 체계적인 전략이 필요하다고 사료되며, 이러한 전략을 바탕으로 효율적인 항공 산업을 선점해야 할 것이다.

• Composites Research
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• v.32 no.1
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• pp.29-36
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• 2019

The purpose of this paper is to suggest a lightweight design for the aluminum extrusion carbody structure of a double deck high-speed train using material substitution and size optimization method. In order to conduct material substitution, the topology optimization was used to determine the application parts of sandwich composites at the carbody structures. The results of analysis showed that sandwich composites could be applied at roof and 2nd underframe. The size optimization was used to determine thickness of the aluminum extruded and carbon/epoxy composite. The design variable, state constraint and objective function were formulated to solve the size optimization, and then, the feasible design was presented by these conditions. The results of the lightweight design showed that the weight of double deck high-speed train hybrid carbody could be reduced by 2.18(17.70%) tons.