• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.1
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• pp.52-57
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• 2007

One of the hot issues in composite patching is to reduce the thermal residual stresses between composite patch and aluminum surface which occurs after bonding of composite patch. In this study, the edge crack patching is adopted for different curing cycles. For the analysis, three layer Mindlin plate elements are used, and Paris' law is adopted to predict the fatigue life of composite patch plate. The analysis results show a good agreement with the experimental fatigue life and this technique can be applied for the prediction of fatigue life of aircraft structures.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.05a
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• pp.167-172
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• 2002

During the operation of military aircraft, maintenance is divided into organizational, intermediate and depot maintenance. In the depot maintenance, after removal of major parts and removable doors, damage assessment is performed. Locating damage, charactering the damage and determining its extent, zoning the damage on the part being repaired and re-evaluation of the damaged area after damage removal. Repair joints are classified by bonded joints and bolted joints, depending on joining material. In this paper, repair method in aging aircraft is investigated and the possibility of application of copmposite patch is surveyed.

• Journal of the Korean Society for Railway
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• v.12 no.1
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• pp.110-114
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• 2009

This study is for the evaluation of compressive strength restoration of sandwich composite laminates with adhesively bonded scarf patches. It was used in this study that the sandwich composite laminate with an aluminum honeycomb core and CF1263 woven fabric carbon/epoxy faces was applied to the car body structure for Korean tiling train. In this study, it was damaged by low velocity impact and repaired using scarf repair method. Then, the compressive strength restoration of assessed by compressive after impact (CAI) test. From the test, it could be known that the compressive strength was restored up to 72% by only scarf repair method and 91% applied by an extra ply over the undamaged one.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2000.04a
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• pp.37-37
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• 2000

복합재료는 높은 무게비 강도 및 강성뿐만 아니라 우수한 재료 특성 때문에 경량화와 구조적 안전성이 요구되는 항공기의 구조재로서 사용이 증대되고 있다. 소형 민용항공기는 구조적 안전성과 함께 제작과 정비, 유지보수의 용이성이 중요시된다. 본 연구에서는 복합재료를 구조재로 사용하였을 때의 성능변화와 경량화 등을 검토하기 위하여 기존의 알루미늄 합금을 이용하여 설계된 소형 프로펠러 경항공기 날개의 구조재로서 복합재료를 사용하여 재설계하였다. 날개의 기본 구조는 스킨, 스파, 웹으로 구성된 상자형 단면으로 설계하였으며 날개의 구조재로서 탄소/에폭시를 사용하여 상용 유한요소해석코드인 NISAII를 이용하여 굽힘, 좌굴 등의 응력해석을 수행하였고 기존 설계된 날개와의 성능비교를 위하여 알루미늄 합금으로 설계된 날개를 모델링하여 해석한 결과와 비교하였다. 비교결과 구조재로 탄소/에폭시를 사용하여 설계된 날개가 무게비 성능면에서 더 우수함을 확인하였다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.793-796
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• 2003

This study dealt with the manufacturing process of self-healing microcapsules for damage repair in polymeric composites. The microcapsule was consisted with a DCPD (dicyclopentadiene) as the healing agent and a urea-formaldehyde resin as the wall section. The size distribution of microcapsules were measured by a particle size analyzer using a laser diffraction technique. Thermal stability of microcapsules was investigated by using a TGA under continuous and isothermal heating conditions. According to the results, these microcapsules were verified to be to thermally stable and have a great potential to be applicable for damage repair in polymeric composites.

• Journal of the Korean Society for Nondestructive Testing
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• v.31 no.1
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• pp.53-61
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• 2011

Edge notched A16061-T6 aluminum was repaired with a GFRP composite patch as a function of the number of stacking, Damage progress of specimen for tension load has been monitored by acoustic emission(AE), AE energy rate, hit rate, amplitude, waveform and 1st peak frequency distribution were analyzed. Fracture processes were classified into Al cracking, Fiber breakage, Resin cracking and Delamination. Displacement of a specimen can be divided into Region I, II and ill according to acoustic emission characteristics. Region II where the patch itself was actually fractured was focused on to clarify the AE characteristics difference for the number of stacking.

• Journal of the Korean Institute of Gas
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• v.20 no.5
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• pp.96-103
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• 2016

Proper repair methods of damaged city gas pipeline is important factor to safely transmit gas and to reduce economical loss caused by failure of gas pipelines. Repair methods such as surfacing, type-A and type-B welding and composite sleeve method have been used to repair damaged city gas pipelines. In this paper, among repair methods, composite sleeve repair methods were conducted since they are rather simple processes and their repair quality is not sensitive to workers' ability compared with other repair methods. We discussed composite repair processes especially using carbon fiber prepregs and the experimental results.

• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.1
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• pp.48-57
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• 2007

The fatigue crack growth behavior of a cracked and patch-repaired Ah2024-T3 panel has been monitored by acoustic emission(AE). The overall crack growth rate was reduced The crack propagation into the adjacent hole was also retarded by introducing the patch repair. AE signals due to crack growth after the patch repair and those due to debonding of the plate-patch interface were discriminated by usiag the principal component analysis. The former showed high center frequency and low amplitude, whereas the latter showed long rise tine, low frequency and high amplitude. This type of AE signal recognition method could be effective for the prediction of fatigue crack growth behavior in the patch-repaired structures with the aid of AE source location.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.2
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• pp.155-162
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• 2005

This paper presents an invetigation into the cause of deterioration of wet surrounding RC structures subjected to checmical attacks such as sewage. The antibacterial-reforming agent is developed after determining the permeability of the RC structure. After application of the anitbacterial-reforming agent through SEM, the permeability, compressive strength properties and the micro-structure of the concrete were evaluated for durability. In addition, the antibacterial-reforming agent was combined with a protective coating for the wet surrounding RC structure and evaluated for durability. The combined effect of the antibacterial-reforming agent and the protective coating were evaluated in field tests in both sewer system and tunnel sites.

• Proceedings of the Korean Society For Composite Materials Conference
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• 1999.11a
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• pp.177-182
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• 1999

사용한 보수.보강재, Rod, Fabric, Strand 형상을 콘크리트 구조물등에 보강재로 사용되어왔다. 이 재료는 해양환경하에서 내식성과 내구성을 갖는 철근및 철골대체용 복합소재와 초고층 경량 연속섬유보강 시멘트 복합재료는 탄소섬유, 아라미드섬유, 유리섬유등의 쉬트(sheet)형상을 신건재, 비자성, 비전도성, 전파차폐용 재료등에 사용할수있다. 그러나 FRP Rod를 내식성이 요구되는 철근 및 철골대체재로 사용할 경우에는 폴리머 매트릭스의 열화, 섬유와 폴리머간 계면 접착강도의 한계, 화재시 내화성, 보강재의 인발성등의 단점들을 갖고있다[1]. (중략)