• 한국추진공학회지
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• 제21권2호
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• pp.94-101
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• 2017

토우프리프레그는 한 가닥의 탄소섬유, 유리섬유, 아라미드 등의 보강섬유에 일정한 비율의 수지가 미리 함침되어 있는 토우 형태의 프리프레그를 의미하며, 필라멘트와인딩 공법을 위한 중간재이다. 최근 고성능 압력용기 개발에 대한 연구가 활발해지면서 기존의 습식 필라멘트와인딩 공법을 대체할 수 있는 건식 와인딩 공법을 위한 소재인 토우프리프레그에 대한 관심이 증대되고 있다. 본 논문에서는 로켓 모터케이스, 수소연료전지 자동차용 연료탱크, 산업용 고성능 압력용기 등 성능과 신뢰성을 동시에 필요로 하는 부품 제조용 소재로 주목받고 있는 탄소섬유 토우프리프레그의 국내외 최신 연구동향에 대하여 살펴보았다.

• Composites Research
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• 제17권6호
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• pp.28-36
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• 2004

복합재료의 성형조건과 재료의 변형간의 관계를 규명하기 위해 PVC 포움-직물 복합재료 샌드위치 구조의 성형공정 중 토우 구조의 미소 변형을 고찰하였다. 실험에 사용한 포움은 4가지 밀도를 가지는 PVC 포움이며, 면재로는 탄소섬유게폭시 프리프레그(3k)를 사용하였다. 디지털 현미경과 이미지 분석 도구를 사용하여 직물 복합재료의 굴곡 각과 토우 진폭 등의 토우 파라메터를 측정하여 서로 비교하였다. 성형 중 포움의 변화가 직물 복합재료 구조의 변형에 미치는 영향을 파악하기 위해 세 가지 온도 조건($25^{\circ}C$, $80{\circ}C$, $125^{\circ}C$)에서 포움의 압축 실험을 수행하였다. 복합재료 토우 구조의 현미경 관찰 결과 토우의 미소 변형은 포움의 밀도와 성형 압력에 따라 서로 다른 경향을 나타내었으며. 특히 포움의 변형 거동에 큰 영향을 받는 것을 확인하였다.

• Ocean and Polar Research
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• 제36권2호
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• pp.179-187
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• 2014

Directly searching for undiscovered hydrothermal vent sites is inefficient due to the practical difficulty of comprehensively imaging vent fields. Thus, most searches for hydrothermal vent sites rely on the detection of hydrothermal plumes from water column observation. Detecting and measuring the hydrothermal plumes are the most efficient way to infer the presence and distribution of hydrothermal vents. Both the array of vertical casting and lateral towing are the most common methods to discover hydrothermal plumes. In this study, we compared results of cast and tow-yo operations along the same section of a spreading center with a distance of 20.5 km in the North Fiji Basin for mapping hydrothermal plumes. Operation of CTD tow-yo provides a detailed pattern of plumes which enable us to locate the hydrothermal vents. On the other hand, identification of hydrothermal activity can be determined effectively by CTD cast with additional analysis of geochemical tracers. Reduction in the operating time is another advantage of CTD cast operation, especially for regional-scale survey. Our results show that the combination of CTD cast and tow-yo would improve the efficiency of the hydrothermal plume survey to locate new hydrothermal vent sites.

• 자원환경지질
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• 제41권1호
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• pp.81-92
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• 2008

Fonualei Rift and Spreading Center(FRSC)와 Mangatolu Triple Junction(MTJ) 칼데라는 활동성 후호분지인 라우(Lau)분지 북동쪽에 위치하고 있다. FRSC에서는 심해 견인 및 표층 자력탐사가 수행되었으며, 심해 견인 자력탐사에서 나타나는 해저 지형과 자력계 고도 사이의 거리 변화 영향을 보정하기 위해 Guspi의 상향연속법을 이용하여 동일한 고도에서 측정한 값으로 변환하였다. Parker and Huestis의 역산 알고리즘을 이용하여 해양지각의 자화를 계산하였고, 이로부터 심해저 열수 분출구 탐사와 해저지각 구조를 파악하고자 하였다. FRSC의 심해 견인 자력탐사 결과 해령에서 주로 나타나는 최대 4.5 A/m의 Central Anomaly Magnetization High(CAMH)가 관측되었으며, 남남서-북북동으로 추정되는 해령의 방향은 라우분지 내 주요 확장축의 방향과 일치하는 경향을 보인다. 또한 FRSC에서는 열수 분출구로 의심되는 - 4.0 A/m의 저자화이상이 발견되었다. MTJ 칼데라$(174^{\circ}00'W\;15^{\circ}20'S)$에서는 표층 자력탐사만이 수행되었고, 남남서-북북동 방향으로 함몰된 화륜과 중앙에서 나타나는 CAMH를 통해 칼데라 중심에 활동성 확장축이 존재하는 것으로 판단된다.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2003년도 춘계학술발표대회 논문집
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• pp.184-187
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• 2003

Complete prediction of second order permeability tensor for three dimensional circular braided preform is critical to understand the resin transfer molding process of composites. The permeability can be predicted by considering resin flow through the multi-axial fiber structure. In this study, permeability tensor for a 3-D circular braided preform is calculated by solving a boundary problem of a periodic unit cell. Flow field through the unit cell is obtained by using a 3-D finite volume method (FVM) and Darcy's law is utilized to obtain permeability tensor. Flow analysis for two cases that a fiber tow is regarded as impermeable solid and permeable porous medium is carried out respectively. It is found that the flow within the intra-tow region of the braided preform is negligible if inter-tow porosity is relatively high but the flow through the tow must be considered when the porosity is low. To avoid checkerboard pressure field and improve the efficiency of numerical computation, a new interpolation function for velocity variation is proposed on the basis of analytic solutions. Permeability of the braided preform is measured through a radial flow experiment and compared with the permeability predicted numerically.

• 대한조선학회논문집
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• 제53권4호
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• pp.315-328
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• 2016

Techniques for determinating hydrodynamic derivatives of underwater tow-fish using CFD(Computational Fluid Dynamics) are described in this paper. Main components of hydrodynamic derivatives are added mass, linear damping and non-linear damping coefficients. In this study, linear and non-linear damping coefficients for translational velocities are settled by CFD analysis. In order to analyze the underwater tow-fish, UlsanFOAM based on open-source CFD code, namely OpenFOAM, is employed. By simulating pitch and yaw angle variation of underwater tow-fish, 6DOF(Degree-of-Freedom) forces and moments are estimated at each attitudes. In order to determinate the hydrodynamic derivatives, curves(forces and moments vs attitude) for CFD results are fitted by least square methods. To demonstrate the applicability of the current approach, two different problems(impulsive side towing and straight towing) are simulated and all results are validated.

• 한국재료학회지
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• 제9권1호
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• pp.30-34
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• 1999

A polyacrylonitrile(PAN)-based carbon fiber tow was heat-treated by directly passing electric current through the tow. The effects of the stretching stress applied during high temperature heat-treatment of PAN-based carbon fibers were investigated by measuring the electric resistance changes taking place during the internal resistance heating. The structure parameters characterizing the stacks of carbon layer, such as interlayer spacing, sizes and orientation of the carbon fibers heat-treated with hot-stretching were evaluated as a function of surface temperature of tow during heat treatment in the range of $1000~2400^{\circ}C$. Though the layer extent in the fiber axis direction depends strongly on the electric resistance, the changes in a crystallite parameter is independent of the longitudinal strain.

• Korea-Australia Rheology Journal
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• 제21권1호
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• pp.71-79
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• 2009

The incomplete saturation and the void formation during the resin infiltration into fibrous porous media in the resin transfer molding process cause failure in the final product during its service. In order to better understand flow behavior during the filling process, a finite-element scheme for transient flow simulation across the micro-structured fibrous media is developed in the present work. A volume-of- fluid (VOF) method has been incorporated in the Eulerian frame to capture the evolution of flow front and the vertical periodic boundary condition has been combined to avoid unwanted wall effect. In the microscale simulation, we investigated the transient filling process in various fiber structures and discussed the mechanism leading to the flow fingering in the case of random fiber distribution. Effects of the filling pressure, the shear-thinning behavior of fluid and the volume fraction on the flow front have been investigated for both intra-tow and the inter-tow flows in dual-scale fiber tow models.

• 한국연초학회지
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• 제5권2호
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• pp.77-82
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• 1983

The ventilation of cigarette samples made by the combination of various acetate tow denier and porous plug wrapping paper have been investigated The ventilation rate increased no longer in the acetate tow with high mono denier and low total denier but changed slightly in that with low mono denier and high total denier when the porosity of plug wrapping paper was more than 6500cm/min. cbar. Tip pressure drop ratio, Y, was significantly influenced by tip ventilation rate, X. i. e., Y = 1.0880-0.0042x The relationships of ventilation rate, $X_v$. and smoke delivery, Y, were as follows; Tar : $Y_r$= -14.0458-0.1650$X_v$ Nicotine : $Y_N$= - 1.1045-0.0125$X_v$ CO : $Y_{co}$=17.2806-0.2090$X_v$

• 로봇학회논문지
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• 제2권3호
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• pp.212-220
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• 2007

This paper proposes a method of avoiding obstacles and tracking a moving object continuously and simultaneously by using new concepts of virtual tow point and fuzzy danger factor for differential wheeled mobile robots. Since differential wheeled mobile robot has smaller degree of freedom to control and are non-holonomic systems, there exist multiple solutions (trajectories) to control and reach a target position. The paper proposes 'fuzzy danger factor' for obstacles avoidance, 'virtual tow point' to solve non-holonomic object tracking control problem for unique solution and three kinds of fuzzy logic controller. The fuzzy logic controller is policy decision controller with fuzzy danger factor to decide which controller's result is more valuable when the mobile robot is tracking a moving object with obstacles to be avoided.