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내크리프성이 향상된 동축 섬유형 변형률 센서의 계측 특성에 관한 연구
온승윤(Seung Yoon On),김성수(Seong Su Kim) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
In this work, a core-shell structured fiber sensor that has high creep resistance and high sensing performance for measuring mechanical strain is prepared by using a dry-jet wet spinning system and simple dip-coating method. The core part of the fiber sensor is made of ultra-high molecular weight polyethylene which has high modulus and strength. Additionally, microwave post-treatment process was introduced for enhancement of creep resistance of fiber sensor. The shell parts of the fiber sensor, electrically conductive layer, were formed by means of dip coating method. To enhance the sensing performance, the sandwich structured MWCNT conductive coating layer was introduced. Single filament tensile tests and creep test are performed to measure the mechanical properties and creep resistance of the fiber sensors, respectively. Finally, sensing performance of sensor fiber was evaluated.
터보 컴프레셔용 복합재료 틸팅 패드 저널 베어링의 특성에 관한 연구
온승윤(Seung Yoon On),유준일(Jun Il You),김성수(Seong Su Kim) 대한기계학회 2016 대한기계학회 춘추학술대회 Vol.2016 No.12
A tilting pad journal bearing is employed to turbine, compressor, pump and generator applications because of its high load carrying capacity, excellent stability and service durability at high operation speed than conventional metal journal bearings. For the high performance under sever operating condition, a tilting pad journal bearing should reduce vibration of the overall bearing systems. Therefore, the bearings are designed to have excellent dynamic characteristic. In this work, a hybrid composite tilting pad journal bearing was fabricated using carbon-fiber/epoxy composite to increase the dynamic properties. The modal analysis was performed to investigate dynamic stability of composite tilting pad. The stiffness and damping coefficient of fluid film at hydrodynamic lubrication state were calculated by finite difference method (FDM). To verify the analysis results, the hydrodynamic lubrication tess of the composite and white metal tilting pad journal bearings were conducted using an industrial test bench. As a result, the composite tilting pad journal bearing effectively reduced vibration and increased stability and durability of the bearing systems that the white metal tilting pad journal bearing.
탄소섬유/폴리아마이드 6,6 복합재료의 기계적 물성 향상
송승아,온승윤,박고은,김성수 한국복합재료학회 2017 Composites research Vol.30 No.6
탄소섬유 강화 열가소성 수지 복합재료(Carbon fiber reinforced thermoplastic composites; CFRTPs)의 물성은 다양한 요인들에 영향을 받는다. 그 중에서도 탄소섬유 표면에 Sizing되어 있는 에폭시(Epoxy) 층은 열가소성수지와 상호 작용(Interaction)이 없어 매우 취약한 계면을 형성하며, 열가소성 수지의 높은 용융 점도(Melting viscosity) 는 탄소섬유 다발(Bundle) 사이로 함침(Impregnation)이 어려워 탄소섬유 강화 복합재료 내부에 기공(Void)를 형성한다. 이와 같이 탄소섬유와 열가소성 수지 간의 낮은 계면전단강도(Interfacial shear strength)은 탄소섬유강화열가소성 복합재료(Carbon fiber reinforced thermoplastic composites; CFRTPs)의 기계적 물성을 저하시키는 가장 중요한 요인 중 하나이다. 따라서, 본 연구에서는 열가소성 수지와의 상호작용이 없는 탄소섬유 표면의 에폭시 층을 열풍을 통해 제거하고, 열가소성 수지의 점도를 낮춰 함침도를 향상시키기 위해서 용액형 열가소성 수지를 제조하여 탄소섬유 표면에 Sizing 처리 함으로써 CFRTPs의 물성을 향상시켰다. CFRTPs의 층간전단강도(Interlaminar shear strength; ILSS) 및 굽힘 강도(Flexural strength)를 통해 이를 검증하였으며, 수지의 함침도는 기공률(Void content) 의 계산을 통해 분석하였다. Mechanical properties of carbon fiber reinforced thermoplastic composites (CFRTPs) are affected by various factors. One of the them are poor compatibility of the epoxy sizing layer on the carbon fiber surface with thermoplastic matrix, which causes the inferior interfacial strength between fibers and matrix. In addition, the high molten-viscosity of thermoplastics attributes to the poor impregnation state. Consequently, many voids in the composite materials were generated, which leads to poor mechanical properties of the thermoplastic composites. In this study, the epoxy sizing on the carbon fiber surface was removed and the polyamide 6,6 solution was coated on the de-sized carbon fiber surface to improve the impregnation state and mechanical properties. Interlaminar shear strength (ILSS) of CFRPTs was estimated by implementing short beam shear tests. In addition, flexural strength was measured and the impregnation state of the composites was evaluated by calculating void content.