• Advanced Composite Materials
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• 제17권2호
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• pp.139-156
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• 2008

This study aims to characterize the dynamic tensile strength of unidirectional carbon/epoxy composites. Two different carbon/epoxy composite systems, the unidirectional T700S/2500 and TR50S/modified epoxy, are tested at the static condition and the strain rate of $100\;s^{-1}$. A high-strain-rate test was performed using a tension-type split Hopkinson bar technique with a specific fixture for specimen. The experimental results demonstrated that both tensile strength increase with strain rate, while the fracture behaviors are quite different. By the use of the rosette analysis and the strain transformation equations, the strain rate effects of material principal directions on tensile strength are investigated. It is experimentally found that the shear strain rate produces the more significant contribution to strain rate effect on dynamic tensile strength. An empirical failure criterion for characterizing the dynamic tensile strength was proposed based on the Hash-in's failure criterion. Although the proposed criterion is just the empirical formula, it is in better agreement with the experimental data and quite simple.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1993년도 추계학술대회 논문집
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• pp.115-121
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• 1993

The carbon fiber epoxy composite materials have some problems, for example, seperation between carbon fiber and epoxy, delamination of lamina etc. Also, the tool wear is very serious. Therefore, we need to improve the shape of drill and condtion of drilling if possible. In this study, machinability of the carbon fiber epoxy composite materials in drilling was experimentlly investigated to establish the efficient shape of drill.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2011년도 춘계학술대회 논문집
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• pp.1247-1248
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• 2011

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 추계학술발표대회 논문집
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• pp.237-240
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• 2002

Amino terminated polyetherimide(ATPEI) has been synthesized by bisphthalic anhydride arid m-phenylenediamine, after that characterized by differential scanning calorimetry(DSC), thermogravimetric analyzer(TGA). Fourier transform (FT-IR) spectroscopy and gel permeation chromatography(GPC). ATPEI was blend to improve the toughness of bisphenol-A type epoxy resin which was cured by nadic methyl anhydride(NMA). The fracture toughness and the molphology of the toughened epoxy resin was evaluated. The toughness of ATPEI modified epoxy resin was higher than that of the PEI modified epoxy resin. In addtion, carbon fiber/ATPEI modified epoxy resin composites were fabricated and the mechanical properties of the resulted composites were investigated.

• Composites Research
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• 제33권1호
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• pp.7-12
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• 2020

지난 10년간 효율적인 방열 재료 개발을 위해 유망한 매트릭스로서 액정 에폭시 수지(Liquid crystalline epoxy, LCER)는 많은 주목을 받아 왔다. 본 연구에서는 LECR중에서 대표적인 4,4-diglycidyloxybiphenyl (DP) 에폭시를 이용한 고분자/SWCNT 복합체의 합성과 제조 및 특성 분석을 포함한 포괄적인 연구를 제시한다. 복합 재료의 열전도 특성을 확인해보기 위해 에폭시 수지와 충전제인 단일벽 탄소나노튜브(Single-wall carbon nanotube, SWCNT)로 구성된 복합체 샘플이 준비되었다. 특히 DP 복합체는, LCER의 고도로 정렬 된 미세 구조로 인해 동일한 필러를 사용하는 상업용 에폭시의 복합체에 비해 높은 열 전도성을 보였다. 또한, DP 복합체의 열전도도는 충전제의 양을 조절하여 제어할 수 있으며, 특히 SWCNT의 함량이 50 wt%인 DP 복합체는 열전도도는 2.008 W/mK로 가장 높은 열전도도를 나타내었다.

• 한국수소및신에너지학회논문집
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• 제29권2호
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• pp.190-196
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• 2018

Carbon fiber/epoxy composites are typical brittle materials and have low impact properties. Recently, it is important to investigate impact characteristics of carbon fiber composites because of increasing use as automobile parts and high pressure hydrogen vessels of fuel cell electric vehicles for light weight. In this study, the low velocity impact properties of carbon fiber/epoxy composites fabricated by a filament winding method are studied. The low velocity impact properties were measured by performing tests according to ASTM D7136. The low velocity impact simulations were carried out using commercial structural analysis software, Abaqus. The absorbed energy and the delamination shapes were compared between the experimental and simulation results. The numerical analysis method showed that the absorbed energy decreased with the reduced number of cohesive elements in the composite models.

• Macromolecular Research
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• 제9권1호
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• pp.20-29
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• 2001

Interfacial adhesion and nondestructive behavior of electrodeposited (ED) carbon fiber rein-forced composites were evaluated using electro-micromechanical techniques and acoustic emission (AE). The interfacial shear strength (IFSS) of the ED carbon fiber/epoxy composites was higher than that of the untreated fiber. This might be expected because of the possibility of chemical or hydrogen bonding in an electrically adsorbed polymeric interlayer. The logarithmic electrical resistivity of the untreated single-carbon fiber composite increased suddenly to infinity when fiber fracture occurred, whereas that of the ED composite increased relatively gradually to infinity. This behavior may arise from the retarded fracture time due to enhanced IFSS. In single- and ten-carbon fiber composites, the number of AE signals coming from interlayer failure of the ED carbon fiber composite was much larger than that of the untreated composite. As the number of the each first fiber fractures increased in the ten-carbon fiber composite, the electrical resistivity increased stepwise, and the slope of the logarithmic electrical resistance increased.

• 한국응용과학기술학회지
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• 제32권1호
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• pp.40-47
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• 2015

Single-walled carbon nanotubes (SWNTs) was modified with various length of linear alkyl chains and passivated to form dielectric filler. The modified SWNTs embedded into epoxy matrix to fabricate a flexible composite with high dielectric constant. The dielectric behavior of the composite was significantly changed with various alkyl chain length(n) of pyrene. The dielectric constant of the epoxy/SWNTs composite significantly increased with respect to increase in length of alkyl chain at the frequency range from 10 to 105Hz (n=12and18).We also found that the passivated epoxy/SWNTs composite with high dielectric constant presented low dielectric loss. The resulted dielectric performances corresponded to de-bundling of nanotubes and their distribution behavior in the matrix in terms of tail length of alkyl pyrene in the passivation layer.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 춘계학술발표대회 논문집
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• pp.219-222
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• 2002

A new designed composite archery bow limbs are developed in this study. The characteristic F-X curve in current recurve archery bow is first studied for a reference. Based on this, a composite archery bow is designed to obtain a higher strain Energy and good vibration performance. Carbon/Epoxy prototype archery bow limbs are made from autoclaving and test on INSTRON 5567 test machine. The experimental results show that the new designed archery bow is powerful and stable.

• Composites Research
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• 제30권6호
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• pp.350-355
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• 2017

Phenylcyclohexyl (PCH) mesogen을 diglycidyl terephthalate의 2,5 위치에 치환시킨 새로운 액정성 에폭시 수지를 설계하였다. 이 물질의 액정성은 DSC(differential scanning calorimetry)와 POM(polarized optical microscopy)으로 분석하였다. 모든 액정성 에폭시 유도체는 가열 및 냉각 시에 모두 smectic상을 나타내는 enantiotropic한 성질을 나타내었다. 액정성 에폭시의 공융 혼합물을 통하여 액정 온도구간을 확장시켰다. 경화된 신규 액정성 에폭시는 $0.4W{\cdot}m^{-1}{\cdot}K^{-1}$의 높은 열전도도를 나타냈다. 높은 열전도도를 갖는 신규 액정성 에폭시는 전자 및 디스플레이용 복합소재로 이용될 것으로 기대된다.