• 한국펄프종이공학회:학술대회논문집
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• 한국펄프종이공학회 2006년도 추계학술발표논문집
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• pp.89-96
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• 2006

To estimate the manufacturing district and generation of ancient paper as a cultural property, fiber orientation is one of the criteria. Image analysis using fast Fourier transform with suitable modifications was demonstrated to be an effective means to determine angle and intensity of fiber orientation as a nondestructive method. Binarization process of microscopic images of paper surface and precise calculation for average Fourier coefficients as an angular distribution by linear interpolation were newly introduced in the procedures to improve the accuracy. This analysis method was applied to digital optical micrographs of paper surfaces. Korea and Japanese traditional hand making papers were well distinguished. Korea and Japanese papers made in the traditional ways showed its own characteristic orientation behavior in accordance with the motion of a bamboo wire.

• 한국자동차공학회논문집
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• 제17권3호
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• pp.35-44
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• 2009

The purpose of this paper is to describe experimental results about the T-joint welding of the high power continuous wave (CW) fiber laser for SAPH steel plate for seat frame of car. The seat rail is a part of seat frame of cars. The assembling method is mostly fix up using a bolt and nut. But this assembling method has many demerits in productivity such as increasing work process and material cost. This paper presents an experimental study about Laser T-Joint weldability of seat rail. Laser welding has many advantages in lightness and saving material costs of seat frame. The laser beam was moved along the work pieces by six axis robot with process optical fiber. The laser beam is focused with a welding head within incident angle $15{\sim}45^{\circ}$ for the purpose of the T-joint welding through two side full penetration. The range of the root gap size is less than ${\leq}0.4mm$. Optical microscopy SEM were performed to observe the micro structures and determine the structures of welded zone.

• 한국정밀공학회지
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• 제21권5호
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• pp.38-45
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• 2004

As optical communication is being substituted for telecommunication, the demand of a large variety of fiber optic components is increasing. V-groove substrates, one of the module components, are used to connect optical fibers to optical planar circuits and to arrange fibers. Their applications are multi-channel optical connectors and optical waveguide fiber coupling, etc. Because these substrates are a critical part of the splitter in a multiplexer and a multi fiber connector, precise and reliable fabrication process is required. For precisely aligning core pitch between fibers, machined core pitch tolerance should be within sub-microns. Therefore, these are generally produced by state-of-the-art micro-fabrication like MEMS. However, most of the process equipment is very expensive. It is also difficult to change the process line for custom designs to meet specific requirements using various materials. For various design specifications such as different values of the V angle and low-priced process, the fabrication method should be flexible and low cost. To achieve this goal, we have suggested a miniaturized machine tool with high accuracy positioning system. Through this study, it is shown that this cutting process can be applied to produce V-groove subtracts. We also show the possibility of using a miniaturized machining system for producing small parts.

• Structural Engineering and Mechanics
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• 제57권1호
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• pp.105-126
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• 2016

In the present study, modelling and vibration control of axially moving laminated Carbon nanotubes/fiber/polymer composite (CNTFPC) plate under initial tension are investigated. Orthotropic visco-Pasternak foundation is developed to consider the influences of orthotropy angle, damping coefficient, normal and shear modulus. The governing equations of the laminated CNTFPC plates are derived based on new form of first-order shear deformation plate theory (FSDT) which is simpler than the conventional one due to reducing the number of unknowns and governing equations, and significantly, it does not require a shear correction factor. Halpin-Tsai model is utilized to evaluate the material properties of two-phase composite consist of uniformly distributed and randomly oriented CNTs through the epoxy resin matrix. Afterwards, the structural properties of CNT reinforced polymer matrix which is assumed as a new matrix and then reinforced with E-Glass fiber are calculated by fiber micromechanics approach. Employing Hamilton's principle, the equations of motion are obtained and solved by Hybrid analytical numerical method. Results indicate that the critical speed of moving laminated CNTFPC plate can be improved by adding appropriate values of CNTs. These findings can be used in design and manufacturing of marine vessels and aircrafts.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 춘계학술발표대회 논문집
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• pp.143-146
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• 2002

Unsized AS-4 carbon fibers were etched by RF plasma and then coated via plasma polymerization in order to enhance adhesion to vinyl ester resin. The gases utilized for the plasma etching were Ar, $N_2 and O_2$, while the monomers used for the plasma polymerization coating were acetylene, butadiene and acrylonitrile. The conditions for the plasma etching and the plasma polymerization were optimized by measuring interfacial adhesion with vinyl ester resin via micro-droplet tests. Among the treatment conditions, the combination of Ar plasma etching and acetylene plasma polymerization provided greatly improved interfacial shear strength (IFSS) of 69MPa compared to 43MPa with as-received carbon fiber. Based on the SEM analysis of failure surface and load-displacement curve, it was assume that the failure might be occurred at the carbon fiber and plasma polymer coating. The plasma etched and plasma polymer coated carbon fibers were subjected to analysis with SEM, XPS, FT-IR or Alpha-Step, and dynamic contact angles and tensile strengths were also evaluated. Plasma polymer coatings did not change tensile strength and surface roughness of fibers, but decreased water contact angle except butadiene plasma polymer coating, possibly owing to the functional groups introduced, as evidenced by FT-IR and XPS.

• Journal of the Korean Wood Science and Technology
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• 제46권4호
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• pp.393-401
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• 2018

Natural fibers derived from lignocellulosic materials are considered to be more environment-friendly than petroleum-based synthetic fibers. Several natural fibers, such as seedpod fibers, have a potential for development, including kapok and balsa fibers. The characteristics of both fibers were evaluated to determine their suitability for specific valuable applications. The purpose of this study was to analyze some important fundamental properties of kapok and balsa fibers, including their dimensions, morphology, chemical components, and wettability. The results showed that the average fiber lengths for kapok and balsa were 1.63 and 1.30 cm, respectively. Kapok and balsa fibers had thin cell walls and large lumens filled with air. The kapok fiber was composed of 38.09% ${\alpha}-cellulose$, 14.09% lignin, and 2.34% wax content, whereas the balsa fiber was composed 44.62% ${\alpha}-cellulose$, 16.60% lignin, and 2.29% wax content. The characteristics of kapok and balsa fibers were examined by X-ray diffraction, Fourier-transform infrared spectroscopy and differential scanning calorimetry analyses. The contact angle of the distilled water on kapok and balsa fibers was more than $90^{\circ}$, indicating that both fibers are hydrophobic with low wettability properties because of to the presence of wax on the fiber surface.

• 비파괴검사학회지
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• 제28권2호
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• pp.157-163
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• 2008

본 논문에서는 대형 구조물의 감시를 위한 새로운 광섬유 경사계를 제시한다. 이 경사계 시스템은 센서 헤드, 광 조절부 그리고 신호처리부로 이루어진다. 또한 본 시스템은 무아레 프린지 현상의 원리를 이용하며 광섬유라는 새로운 광측정 장치를 적용하였다. 이를 통해, 센서 시스템은 가격이 저렴하고 전자기학 잡음에 강하며 설치가 용이해 졌다. 실제로 본 논문에서는 저비용의 광전자 구동 시스템을 포함한 실제 시제품을 성공적으로 개발하였다. 그리고 실제 실험을 통해 센서의 선형성을 포함한 성능을 검증하였고 이를 통해 실제 토목구조물의 처짐각을 측정할 수 있는 광섬유 경사계 시스템으로서의 가능성과 성능을 입증하였다.

• 한국가스학회지
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• 제15권1호
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• pp.35-39
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• 2011

본 논문에서는 FEV 차량용 복합소재 연료탱크의 탄소섬유 적층두께에 따라 달라지는 강도안전성에 미치는 기여율의 영향을 해석하고자 한다. 기여율에 의한 영향을 FEM 모델링으로 고찰하기 위해, 복합소재 연료탱크의 알루미늄 라이너와 탄소섬유 적층에 작용하는 von Mises 등가응력을 후프방향과 헤리컬방향에 대하여 각각 계산 하였다. FEM 해석결과에 따르면, 알루미늄 라이너에 작용하는 등가응력 기여율은 후프방향으로는 77.5%, $70^{\circ}C$ 경사진 헤리컬방향으로는 18.11%, $12^{\circ}C$ 경사진 헤리컬방향으로는 4.39%로 각각 작용하는 것으로 나타났다. $12^{\circ}C$ 경사진 탄소섬유의 적층 두께비가 후프방향 적층 두께비의 42% 정도로 높게 유지됨에도 불구하고 알루미늄 라이너 소재에서 보여준 기여율 경향은 탄소섬유 적층의 강도안전성에 대해서도 유사한 것으로 나타났다. 결과적으로, 탄소섬유 연료탱크의 강도안전성은 탄소섬유 적층의 두께보다 와인딩 각도에 의해 더 많은 영향을 받는다는 계산결과를 보여주고 있다.

• Composites Research
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• 제34권5호
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• pp.305-310
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• 2021

섬유강화복합재료의 기계적물성은 섬유의 체적분율 및 사이징제 조건에 의한 계면강도에 영향을 받는다. 최적의 계면은 기지층에서 강화재로의 기계적 응력을 효과적으로 전달하여 응력 집중을 완화하고 결과적으로 복합재료의 성능을 향상시킬 수 있다. 본 논문에서는 사이징제 조건 및 섬유체적분율에 따른 에폭시 수지와 유리섬유 간의 젖음성 및 계면강도를 평가하였다. 정적 및 동적접촉각을 이용하여 사이징제가 다른 유리섬유와 에폭시 수지의 표면에너지를 계산하였고, 이를 활용하여 접착일을 계산하였다. 유리섬유 토우 캐필러리 시험법을 이용하여 젖음성을 평가하였고, 마이크로드롭렛 인발시험을 통해 계산된 계면전단강도를 이용하여 계면강도를 평가하였다. 최종적으로 젖음성과 계면강도를 활용하여 최적의 유리섬유강화 복합재료 제작 조건을 확인하였다.

• 한국기후변화학회지
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• 제7권3호
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• pp.249-256
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• 2016

Porous $Al_2O_3$ hollow fiber membranes were successfully prepared by dry-wet spinning/sintering method. The SEM image shows that the $Al_2O_3$ hollow fiber membrane consists mostly of sponge pore structure. The contact angle and the breakthrough pressure were $126^{\circ}$ and 1.91 bar, respectively. This results indicate that the $Al_2O_3$ hollow fiber membranes were successfully modified to hydrophobic surface. The hydrophobic modified $Al_2O_3$ hollow fiber membranes were assembled into a membrane contactor system to separate $CO_2$ from a model gas mixture of the flue gas at elevated gas velocity. The $CO_2$ absorption flux was enhanced when the gas velocity increased from $1{\times}10^{-3}$ to $6{\times}10^{-3}$ m/s. Whereas the $CO_2$ absorption flux was decreased with the number of hollow fiber membrane of a module because of the concentration polarization. Furthermore, we developed an lab-scale $Al_2O_3$ hollow fiber membrane contactor modules and their system (i.e., $CO_2$ absorption using the $Al_2O_3$ membrane and monoethanolamine (MEA)) that could dispose of over $0.02Nm^3/h$ mixture gas (15% $CO_2$) with the removal efficiency higher than 95%. The results can be useful in a field of the membrane contactor for $CO_2$ separation, helping to design and extend a equipment.