• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제37회 하계학술대회 초록집
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• pp.109-109
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• 2009

• Composites Research
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• 제36권3호
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• pp.186-192
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• 2023

최근, 철도차량 분야에서는 경량화 및 운송 효율화를 위해 복합재 활용에 대한 관심이 높아지고 있다. 이에 따라 다양한 차량 부품에 복합재를 적용하고자 하는 연구 및 상용화 개발이 활발히 이루어지고 있으며, 복합재 적용에 대한 품질 검증을 위해 완성품의 기계적 성능 평가와 같은 사후 측정을 중심으로 평가가 이루어지고 있다. 하지만, 제작 품질에 큰 영향을 미치는 요소인 복합재 성형 과정에서 발생하는 열과 응력에 대한 분석은 미비한 상황이다. 따라서, 본 연구에서는 철도차량용 복합재 부품의 성형 품질을 검증하기 위하여 가장 활발히 사용되는 복합재 내장재 패널 2종(라미네이트 패널, 샌드위치 패널)에 대한 성형 품질 분석을 진행하였다. 이를 위해 복합재 내부 적용에 용이한 FBG 광섬유 센서를 이용하여 성형 과정 동안 온도 및 변형률 변화를 모니터링 하고, 성형 완료 후 발생하는 잔류 변형률 값을 측정하였다. 결과적으로, 과열 현상과 과도 잔류응력이 발생하지 않은 것을 확인함으로써 철도차량용 복합재 내장재 패널의 우수한 성형 품질을 검증하였다.

• Composites Research
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• 제15권2호
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• pp.11-17
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• 2002

우수한 동적 감지특서을 갖는 압전필름센서는 구조 건전성 모니터링이나 평가와 같은 구조물과 재료의 변화를 분석하는데 사용될 수 있다. 압전필름센서의 이러한 특성을 이용하여 Gr/Ep 복합재 평판의 충격 손상개시를 모니터링하였다. 압전필름센서와 스트레인게이지를 Gr/Ep 복합재 평판에 부착하여 다양한 조건의 에너지에 대한 충격시험을 낙하식 충격 시험기를 사용하여 수행하였다. 충격시험을 수행하는 동안 영구압입, 기지균열, 층간분리와 같은 충격 손상개시를 예측하기 위하여 센서신호를 분석하였다. 충격에너지를 초기 손상이 발생할 수 있는 크기 이상으로 증가시키면 손상의 개시와 진전에 대한 정보를 포함하는 특정 센서 신호를 관찰할 수 있었다. 특히, 압전필름세서는 스트레인게이지 보다 충격 손상개시 및 진전에 대한 좋은 감지 특성을 보여주었다.

• 센서학회지
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• 제30권6호
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• pp.388-394
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• 2021

The conventional microelectromechanical system (MEMS) process has been used to fabricate sensors with high costs and high-volume productions. Emerging 3D printing can utilize various materials and quickly fabricate a product using low-cost equipment rather than traditional manufacturing processes. 3D printing also can produce the sensor using various materials and design its sensing structure with freely optimized shapes. Hence, 3D printing is expected to be a new technology that can produce sensors on-site and respond to on-demand demand by combining it with open platform technology. Therefore, this paper reviews three standard 3D printing technologies, such as Fused Deposition Modeling (FDM), Direct Ink Writing (DIW), and Digital Light Processing (DLP), which can apply to the sensor fabrication process. The review focuses on strain/load sensors having both sensing material features and structural features as well. NCPC (Nano Carbon Piezoresistive Composite) is also introduced as a promising 3D material due to its favorable sensing characteristics.

• Composites Research
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• 제33권2호
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• pp.50-54
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• 2020

소프트 로봇 및 웨어러블 소자는 대변형 및 큰 유연성을 요구한다. 이에 따라, 소프트 로봇 또는 웨어러블 소자에 부착하여 사용할 수 있는 신축성 스트레인 센서의 필요성이 대두되고 있다. 본 연구에서는 폴리우레탄과 은나노꽃입자를 혼합하여 신축성과 전기전도성을 갖는 복합 섬유를 제조하였다. 이러한 복합 섬유는 스트레인에 따라 섬유의 저항이 변하게 되어 신축성 스트레인 센서로 가능성이 높다. 복합 섬유를 신축성 스트레인 센서로 활용하기 위해서, 복합 섬유의 기계적, 전기적 특성을 측정, 분석하였다.

• 한국재료학회지
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• 제29권2호
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• pp.121-128
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• 2019

Supercapacitors are attracting much attention in sensor, military and space applications due to their excellent thermal stability and non-explosion. The ionic liquid is more thermally stable than other electrolytes and can be used as a high temperature electrolyte, but it is not easy to realize a high temperature energy device because the separator shrinks at high temperature. Here, we report a study on electrochemical supercapacitors using a composite electrolyte film that does not require a separator. The composite electrolyte is composed of thermoplastic polyurethane, ionic liquid and fumed silica nanoparticles, and it acts as a separator as well as an electrolyte. The silica nanoparticles at the optimum mass concentration of 4wt% increase the ionic conductivity of the composite electrolyte and shows a low interfacial resistance. The 5 wt% polyurethane in the composite electrolyte exhibits excellent electrochemical properties. At $175^{\circ}C$, the capacitance of the supercapacitor using our free standing composite electrolyte is 220 F/g, which is 25 times higher than that at room temperature. This study has many potential applications in the electrolyte of next generation energy storage devices.

• 비파괴검사학회지
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• 제33권5호
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• pp.459-464
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• 2013

Structures can be evaluated their health status by allowable loading criteria. These criteria can be determined by the maximum strain. Therefore, in order to detect this maximum strain of structures, fiber optic Bragg grating(FBG) sensor probes are newly designed and fabricated to perform the memorizing detection even if the sensor system is on-and-off. The probe is constructed with an FBG optical fiber embedded in silver epoxy. When the load is applied and removed on the structure, the residual strain remains in the silver epoxy to memorize the maximum strain effect. In this study, a commercial Al-foil bonded FBG sensor probe was tested to investigate the detection feasibility at first. FBG sensor probes with silver epoxy were fabricated as three different sizes. The detection feasibility of maximum strain was studied by doing the tensile tests of CFRP specimens bonded with these FBG sensor probes. It was investigated the sensitivity coefficient defined as the maximum strain divided by the residual strain. The highest sensitivity was 0.078 of the thin probe having the thickness of 2 mm.

• 센서학회지
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• 제17권5호
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• pp.329-337
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• 2008

Simple, small and portable oxygen sensors were fabricated by tape casting technique. Yttria stabilized zirconia containing cordierite ceramics (YSZC) were used as a porous diffused layer of oxygen in pumping cell. Yttria stabilized zirconia (YSZ) solid electrolyte, YSZC porous diffusion layer and heater-patterned ceramic sheets were prepared by co- firing method. Limit current characteristics and the linear relationship of current to oxygen concentration were observed. Viscosity variation of the slurries both YSZ and YSZC showed a similar behavior, but micro pores in the fired sheet were increased with increasing of the cordierite amount. Molecular diffusion was dominated due to the formation of large pores in porous diffusion layer. The plateau range of limit current in porous-type oxygen sensor was narrow than the one of aperture-type oxygen sensor. However limit current curve was appeared in porous-type oxygen sensor even at the lower applied voltage. The plateau range of limit-current was widen as increasing the thickness of porous diffusion layer of the YSZ containing cordierite. Measuring temperature of $600{\sim}650^{\circ}C$ was recommended for limit-current oxygen sensor. Porous diffusion layer-type oxygen sensor showed faster response than the aperture-type one and was stable up to 30 days running without any crack at interface between the layers.

• Advances in aircraft and spacecraft science
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• 제5권4호
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• pp.499-513
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• 2018

One of the major problems in glass fiber reinforced epoxy (GFRE) composite pipes is the durability under water absorption. This condition is generally recognized to cause degradations in strength and mechanical properties. Therefore, there is a need for an intelligent system for detecting the absorption rate and computing the mass of water absorption (M%) as a function of absorption time (t). The present work represents a new non-destructive evaluation (NDE) technique for detecting the water absorption rate by evaluating the dielectric properties of glass fiber and epoxy resin composite pipes subjected to internal hydrostatic pressure at room temperature. The variation in the dielectric signatures is employed to design an electrical capacitance sensor (ECS) with high sensitivity to detect such defects. ECS consists of twelve electrodes mounted on the outer surface of the pipe. Radius-electrode ratio is defined as the ratio of inner and outer radius of pipe. A finite element (FE) simulation model is developed to measure the capacitance values and node potential distribution of ECS electrodes on the basis of water absorption rate in the pipe material as a function of absorption time. The arrangements for positioning12-electrode sensor parameters such as capacitance, capacitance change and change rate of capacitance are analyzed by ANSYS and MATLAB to plot the mass of water absorption curve against absorption time (t). An analytical model based on a Fickian diffusion model is conducted to predict the saturation level of water absorption ($M_S$) from the obtained mass of water absorption curve. The FE results are in excellent agreement with the analytical results and experimental results available in the literature, thus, validating the accuracy and reliability of the proposed expert system.

• 한국재료학회지
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• 제19권11호
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• pp.607-612
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• 2009

We investigated the effects of Co doping on the NO gas sensing characteristics of ZnO-carbon nanotube (ZnO-CNT) layered composites fabricated by coaxial coating of single-walled CNTs with ZnO using pulsed laser deposition. Structural examinations clearly confirmed a distinct nanostructure of the CNTs coated with ZnO nanoparticles of an average diameter as small as 10 nm and showed little influence of doping 1 at.% Co into ZnO on the morphology of the ZnO-CNT composites. It was found from the gas sensing measurements that 1 at.% Co doping into ZnO gave rise to a significant improvement in the response of the ZnO-CNT composite sensor to NO gas exposure. In particular, the Co-doped ZnO-CNT composite sensor shows a highly sensitive and fast response to NO gas at relatively low temperatures and even at low NO concentrations. The observed significant improvement of the NO gas sensing properties is attributed to an increase in the specific surface area and the role as a catalyst of the doped Co elements. These results suggest that Co-doped ZnOCNT composites are suitable for use as practical high-performance NO gas sensors.