• Title/Summary/Keyword: 섬유 방향성

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Directional Solidification of Fibrous Eutectic System (섬유상 공정계의 일방향응고)

  • 김신우
    • Proceedings of the Materials Research Society of Korea Conference
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    • 2003.11a
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    • pp.42-42
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    • 2003
  • 두개의 다른 고상이 동시에 액상으로부터 응고되는 공정합금에 일방향응고를 적용함에 따라 응고방향으로 규칙적으로 잘 배열된 복합재료를 만들 수 있다. 이렇게 방향성을 가지고 응고된 공정조직은 여러 가지 기계적, 전기적, 자기적 특수분야에 이용될 수 있다. 그런데 공정조직의 상간격은 재료의 기계적, 물리적 성질과 밀접한 관계를 가지며 응고속도, 온도기울기와 같은 일방향응고의 변수에 따라 결정된다. 그래서 본 연구에서는 금속합금계와 유사한 섬유상 공정조직을 보이는 NaNO$_3$-NaCl계를 이용하여 공정조직의 미세구조와 일방향응고 변수와의 관계를 조사하였다. 또한 액상으로부터 시간에 따른 냉각곡선으로부터 공정온도와 공정조성부근의 부분상태도를 구하였다. 그리고 응고녹도(V)에 따른 섬유상간격(λ$_{E}$ )의 실험적 관계식을 두가지의 온도기울기에 대하여 구하여 금속재료의 결과식과 비교, 검토하였다.

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PREPARATION OF ELECTROCONDUCTIVE POLY(THIOPHENE-CO-PYRROLYL UNDECANOIC ACID) LANGMUIR-bLODGETT FILMS (Poly(thiophene-co-pyrrolyl undecanoic acid) LB film 제조 및 성질)

  • 장지임;박연흠;김건형;조원호
    • Proceedings of the Korean Fiber Society Conference
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    • 2003.10b
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    • pp.159-160
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    • 2003
  • 금속과 유사한 전도성을 가진 공액이중결합의 전기전도성 고분자를 사용한 Langmuir-Blodett (LB) 막의 제조에 관한 연구는 그 범위가 넓으며, 지금까지 많은 연구 논문들이 보고되고 있다[1]. 특히 전도성이 뛰어난 polyaniline, polypyrrole, polythiophene은 전도성과 stability가 우수하여 전기 전도성 LB 막에 대한 연구들이 많이 진행되어 왔다[2]. 본 연구에서는 이와 같은 전기전도성 유기물질을 사용한 전도성 LB막이 수직방향에 비해 수평방향의 전기전도도가 크다는 전기적 장점을 이용하여 전도성 LB막을 제조하기 위해 새로운 전도성 고분자를 합성하여 전기 전도성을 띄는 LB 막을 제조하였다[3,4]. (중략)

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Prediction Algorithm for Transverse Permeability of Unidirectional Fiber Reinforced Composites with Electric-Hydraulic Analogy (전기-유압 유사성을 활용한 단방향 섬유 강화 복합재료의 수직 방향 투수 계수 예측 알고리즘)

  • Bae, Sang-Yun;Jo, Hyeonseong;Kim, Seong-Su
    • Composites Research
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    • v.35 no.5
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    • pp.334-339
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    • 2022
  • This study suggests the prediction algorithm for transverse permeability, represented the flow resistance during the manufacturing process of composite, of unidirectional continuous fiber reinforced plastics. The cross-sectional shape of representative volume element (RVE) is considered to reflect fiber arrangement. The equivalent length is used as a factor to express the change of resin flow according to fiber arrangement. The permeability prediction algorithm is created by grafting the Electro-Hydraulic analogy and validity is confirmed. The code for permeability prediction was composed by means of MATLAB and Python, flow analysis was performed by using FLUENT. The algorithm was verified as the permeability results obtained through Algorithm and numerical analysis were almost identical to each other, and the calculation time was reduced around 1/450 compared to the numerical analysis.

Prediction of Fracture Strength of Woven CFRP Laminates According to Fiber Orientation (평직 CFRP 적층복합재료의 섬유배열각도에 따른 파괴강도 예측)

  • Kang, Min-Sung;Park, Hong-Sun;Choi, Jung-Hun;Koo, Jae-Mean;Seok, Chang-Sung
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.36 no.8
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    • pp.881-887
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    • 2012
  • CFRP composite materials have been widely used in various fields of engineering because of their excellent properties. They show high specific stiffness and specific strength compared with metallic materiasl. Woven CFRP composite materials are fabricated from carbon fibers with two orientation angles ($0^{\circ}/90^{\circ}$), which influences the mechanical properties. Therefore, woven CFRP composite materials show different types of fracture behavior according to the load direction. Therefore, the fracture behavior of these materials needs to be evaluated according to the load direction when designing structures using these materials. In this study, we evaluate the fracture strength of plain-woven CFRP composite materials according to the load direction. We performed tests for six different angles (load direction: $0^{\circ}/90^{\circ}$, $30^{\circ}/-60^{\circ}$, $+45^{\circ}/-45^{\circ}$) and estimated the fracture strength for an arbitrary fiber angle by using the modified Tan's theory and harmonic function.

Assessment of Transmissivity of Blended Geotextiles for Drainage (배수용 혼합 지오텍스타일의 수평투수성 평가)

  • 전한용;목문성;주용수;유중조
    • Proceedings of the Korean Fiber Society Conference
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    • 2001.10a
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    • pp.428-431
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    • 2001
  • 토목합성재료(Geosynthetics) 중 배수용으로 사용되는 재료는 기능상 유체의 흐름을 수평방향으로 유도하는 재료를 의미하며, 일반적으로 저장된 유체를 수직으로 이동시키는 필터기능을 가지는 1,000g/㎡ 미만의 지오텍스타일(geotextiles)과 수평방향의 유도로를 확보한 지오네트(geonets)를 결합시킨 지오네트 복합제품이 사용되고 있다. 이러한 배수용 토목합성재료는 쓰레기 매립장의 건설 시 침출수의 외부유출을 차단하기 위하여 설치하는 차수막인 지오멤브레인(geomembranes)을 매립된 쓰레기 하중 및 외부의 충격으로부터 보호하는 용도로 사용된다. (중략)

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Tribological Properties of Laminated Fiber Orientation in Carbon Fiber/Epoxy Composites for Reflecting Material of the Electromagnetic Wave (전자파 반사재료로 사용되는 탄소섬유/에폭시 복합재료의 적층 탄소섬유 방향성이 마찰특성에 미치는 영향)

  • Chun, Sang-Wook;Gimm, Youn-Myoung;Kang, Ho-Jong
    • Applied Chemistry for Engineering
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    • v.10 no.5
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    • pp.778-783
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    • 1999
  • The effect of carbon fiber orientation on the tribological properties of carbon fiber/epoxy composites used as a reflecting material for the electromagnetic wave has been investigated. It was found that the carbon fiber/epoxy composite which slides normal to prepreg lay-up direction had less friction and wear that those slides parallel to prepreg fiber lay-up direction due to the increase of delamination between carbon fiber and epoxy. Composite with unidirectional orientation($0/0^{\circ}$) had higher tribological properties than those with multidirectional orientation($0/45/90/-45^{\circ}$ and $0/90^{\circ}$) when the sliding direction was normal to prepreg lay-up direction. This was caused by the debonding between carbon fiber and epoxy which is proportional to contact area between the sliding surface and carbon fiber. Opposite results have been found when the sliding direction was parallel to prepreg lay-up direction due tot he tensile force applied on carbon fiber. In addition, it was shown that wear factor increased with increasing sliding velocity but the friction coefficient did not depend upon the sliding velocity.

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Performance Evaluation of Composite Safety Barrier for Bridge by Vehicle Impact Simulation (차량 충격 시뮬레이션을 통한 복합소재 교량용 방호울타리의 성능 분석)

  • Kim, Seung-Eock;Jeon, Shin-Youl;Hong, Kab-Eui;Lee, Min-Chul
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.24 no.5
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    • pp.499-506
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    • 2011
  • In this study, the performance of composite safety barriers was evaluated through computer simulation. A composite safety barrier of SB4 grade was modeled. The MAT58 material model provided by LS-DYNA software was used to model composite material. The performance of composite material varies according to fiber, resin type, and fiber direction. Polyurethane resin and glass fiber were used. The performance of three different stacking designs was evaluated by carrying out vehicle impact simulation. The performance evaluation based on the vehicle crash manual includes the structural strength performance, the passenger protection performance, the vehicle behavior after crash, scattering of the guardrail. As the result of the finite element analysis, the barrier composed of the more transverse direction fibers shows the better performance on the impact simulation.

Variation of the Group Velocity of Lamb Wave $S_o$ Mode with the Propagating Direction in the Laminated Unidirectional CFRP Plates (단일방향 탄소섬유복합재료 적층 판에서 전파 방향에 따른 램파 $S_o$ 모드의 군속도의 변화)

  • Kim Young H.;Lee Seung Seok;Kim Ho Chul;Lee Jeong Ki
    • Composites Research
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    • v.18 no.1
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    • pp.38-44
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    • 2005
  • In this paper, the group velocity dispersion curves of the $S_o$ symmetric mode in unidirectional CFRP plate was calculated as varying the propagating direction. The group velocity curve was obtained with the group velocities of the $S_o$ symmetric mode corresponding to 0.2 MHz-mm under the first cut-off frequency in the dispersion curves, and corrected by introducing the slowness curve. The velocities of the $S_o$ symmetric mode in the unidirectional CFRP plate were measured as varying the propagating direction and compared with the col?rotted group velocity curve. The measured velocities were good agreement with the corrected group velocity curve except near the fiber direction which was called the cusp region. It implies that the direction of the group velocities incline toward the fiber direction of the unidirectional CFRP plates when the propagation direction is not accorded with the principal axis. It is supposed that this phenomenon rerults from the preferential propagating the energy toward the direction with the faster propagation velocity.

Realistic Prediction of Post-Cracking Behaviour in Synthetic Fiber Reinforced Concrete Beams (합성섬유보강 콘크리트 보의 균열 후 거동 예측)

  • 오병환;김지철;박대균;원종필
    • Journal of the Korea Concrete Institute
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    • v.14 no.6
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    • pp.900-909
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    • 2002
  • Fibers play a role to increase the tensile strength and cracking resistance of concrete structures. The post cracking behavior must be clarified to predict cracking resistance of fiber reinforced concrete. The purpose of this study is to develop a realistic analysis method for the post cracking behavior of synthetic fiber reinforced concrete members. For this purpose, the cracked section is assumed to behave as a rigid body and the pullout behavior of single fiber is employed. A probabilistic approach is used to calculate effective number of fibers across crack faces. The existing theory is compared with test data and shows good agreement. The proposed theory can be efficiently used to describe the load-deflection behavior, moment-curvature relation, load-crack width relation of synthetic fiber reinforced concrete beams.

Temperature-Dependency of Tensile Properties of GFRP Composite for Wind Turbine Blades (풍력 발전 블레이드 복합재 GFRP의 인장 특성의 온도 의존성)

  • Huh, Yong-Hak;Kim, Jong-Il;Kim, Dong-Jin;Lee, Gun-Chang
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.36 no.9
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    • pp.1053-1057
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    • 2012
  • In this study, the temperature-dependency of the tensile properties of a glass fiber reinforced plastic (GFRP) used in wind turbine blades was examined. The tensile strength, elastic modulus, and Poisson's ratio of the tensile specimen manufactured from uniaxial ($0^{\circ}$) and triaxial ($0/{\pm}45^{\circ}$) laminate composite plates were measured at four different testing temperatures-room temperature, $-30^{\circ}C$, $-50^{\circ}C$, and $60^{\circ}C$. It was found that the tensile strengths and elastic moduli of the uniaxial laminates were greater than those of the triaxial laminates over the testing temperature range. The tensile strength of the two laminates was significantly dependent on the testing temperature, while the dependency of the elastic modulus on the temperature was insignificant. Furthermore, it could be considered that the Poisson's ratio changed slightly with a change in the testing temperature.