• Title/Summary/Keyword: Epoxy composites

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Influence of Oxyfluorination on Physicochemical Characteristics of Carbon Fibers and their Reinforced Epoxy Composites

  • Seo, Min-Kang;Park, Soo-Jin
    • Macromolecular Research
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    • v.17 no.6
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    • pp.430-435
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    • 2009
  • The effect of oxyfluorination temperature on the surface properties of carbon fibers and their reinforced epoxy composites was investigated. Infrared (IR) spectroscopy results for the oxyfluorinated carbon fibers revealed carboxyl/ester (C=O) and hydroxyl (O-H) groups at 1632 and 3450 $cm^{-1}$, respectively, and that the oxyfluorinated carbon fibers had a higher O-H peak intensity than that of the fluorinated ones. X-ray photoelectron spectroscopy (XPS) results indicated that after oxyfluorination, graphitic carbon was the major carbon functional component on the carbon fiber surfaces, while other functional groups present were C-O, C=O, HO-C=O, and $C-F_x$. These components improved the impact properties of oxyfluorinated carbon fibers-reinforced epoxy composites by improving the interfacial adhesion between the carbon fibers and the epoxy matrix resins.

Influence of MWCNTs on Fracture Toughness of MWCNTs/Nickel-Pitch Fiber/Epoxy Composites

  • Yim, Yoon-Ji;Park, Soo-Jin
    • Composites Research
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    • v.28 no.6
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    • pp.361-365
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    • 2015
  • The influence of MWCNTs on fracture toughness properties of MWCNTs/Nickel-Pitch Fibers/epoxy composites (MWCNTs/Ni-PFs/epoxy) was investigated according to MWCNTs content. Nickel-Pitch-based carbon fibers (Ni-PFs) were prepared by electroless nickel-plating. The surface properties of Ni-PFs were determined by scanning electron microscopy (SEM) and X-ray photoelectron spectrometry (XPS). The fracture toughness of MWCNTs/Ni-PFs/epoxy was assessed by critical stress intensity factor ($K_{IC}$) and critical strain energy release rate ($G_{IC}$). From the results, it was found that the fracture toughness properties of MWCNTs/Ni-PFs/epoxy were enhanced with increasing MWCNTs content, whereas the value decreased above 5 wt.%. MWCNTs content. This was probably considered that the MWCNTs entangled with each other in epoxy due to an excess of MWCNTs.

The effect of MWCNTs on the mechanical properties of woven Kevlar/epoxy composites

  • Taraghi, Iman;Fereidoon, Abdolhossein;Mohyeddin, Ali
    • Steel and Composite Structures
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    • v.17 no.6
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    • pp.825-834
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    • 2014
  • This manuscript presents an experimental investigation on the effect of Multi-walled carbon nanotubes (MWCNTs) addition on the tensile, flexural and impact properties of woven Kevlar fabric reinforced epoxy composites. MWCNTs were dispersed in the epoxy resin by sonication technique and the samples were fabricated by hand layup laminating procedure. Scanning electron microscopy (SEM) was used to characterize the microstructure of produced samples. The effects of adding small amounts (${\leq}1%$) of MWCNT on the tensile, flexural and impact (Izod) behaviors of laminated composites were analyzed. Results revealed that MWCNTs enhanced the Young's modulus up to 20%, bending modulus up to 40%, and impact strength up to 45% in comparison with woven Kevlar fabric/epoxy composites. It was found that the maximum improvements in mechanical properties were happened for 0.5 wt.% MWCNT.

An Estimation of Life Time in Epoxy Composites Using Weibull Distribution (와이블 분포를 이용한 에폭시 복합체의 수명시간 예측)

  • 오현석;이동규;장인범;박건호;김용주;이준웅
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.360-363
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    • 1997
  • The method of estimating life time of epoxy composites which be widely used for transformers has been studied in this paper. The breakdown properties of specimens are observed by appling high AC voltage at the room temperature from a series of the experiments. Afterwards, the breakdown time was determined under the constant voltage below the lowest breakdown voltage. Also, V-t properties were found out using weibull distribution widely used in the applications of discrete data for estimating life time of epoxy composites and life exponent n was gained properly. when life exponent is gained is found out, the tong breakdown life time at used voltage can be estimated from breakdown experiments in short time using reverse law of n power.

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Evaluation of Mode II Interlaminar Fracture Toughness for Carbon Fabric/Epoxy Composites for Tilting Train Carbody (틸팅열차 차체8 탄소섬유직물/에폭시 복합재의 모우드 II 층간파괴인성 평가)

  • Yoon Sung-Ho;Lee Eun-Dong;Heo Kwang-Soo;Jung Jeong-Cheol;Shin Kwang-Bok
    • Journal of the Korean Society for Railway
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    • v.8 no.2
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    • pp.195-201
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    • 2005
  • Mode II interlaminar fracture behaviors of carbon fabric/epoxy composites, which are applicable to tilting train carbodies, was investigated by the ENF (End notched flexure) test. The specimens were made of CF3327 plain woven fabric with epoxy and a starter delamination at one end was made by inserting Teflon film with the thickness of 12.5$mu$m or 25.0$mu$m. The equation for mode II interlaminar fracture toughness was suggested based on the effective crack length from the compliance of load-displacement curve. Mode II interlaminar fracture toughness was evaluated for several types of the specimens. Also crack propagating behaviors and fracture surfaces were examined through an optical travelling scope and a scanning electron microscope.

Compressive Behavior of Carbon/Epoxy Composites under High Pressure Environment-Strain Rate Effect (고압환경에서 탄소섬유/에폭시 복합재의 압축거동에 대한 연구-변형률 속도 영향)

  • 이지훈;이경엽
    • Journal of the Korean Society for Precision Engineering
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    • v.21 no.4
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    • pp.148-153
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    • 2004
  • It is well-known that the mechanical behavior of fiber-reinforced composites under hydrostatic pressure environment is different from that of atmospheric pressure environment. It is also known that the mechanical behavior of fiber-reinforced composites is affected by a strain rate. In this work, we investigated the effect of strain rate on the compressive elastic modulus, fracture stress, and fracture strain of carbon/epoxy composites under hydrostatic pressure environment. The material used in the compressive test was unidirectional carbon/epoxy composites and the hydrostatic pressures applied was 270㎫. Compressive tests were performed applying three strain rates of 0.05%/sec, 0.25%/sec, and 0.55%/sec. The results showed that the elastic modulus increased with increasing strain rate while the fracture stress was little affected by the strain rate. The results also showed that the fracture strain decreased with increasing strain rate.

A Study on the Dielectric Properties of Epoxy Composites with Frequency Variation (주파수 변화에 따른 에폭시 복합체의 유전특성에 관한 연구)

  • 김상걸;이동규;안준호;이상극;오현석;박건호;박우현;이기식;이준웅
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.813-816
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    • 2001
  • In this paper, the dielectric properties of epoxy composites used for transformers are studied. The dielectric permittivity and loss of specimen are measured at the frequency range of 30[Hz]∼1[MHz] about temperature 20[$^{\circ}C$],100[$^{\circ}C$] and 140[$^{\circ}C$] respectively from a series of experiments. When the filler is added, between epoxy and silica is formed interface. Therefore, observed higher values of dielectric permittivity and loss in filled epoxy are attributed to MWS polarization effect. Also, glass transition temperature was shifted to higher temperature and value of dielectric permittivity and loss were decreased due to 2nd curing. Deformation of interfacial state is improved and value of dielectric permittivity and loss were decreased at low frequency region by the surface treatment of fillers with silane coupling agents.

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An Analysis of Insulating Reliability in Epoxy Composites for Molding Materials of PT

  • Yang, Jeong-Yun;Park, Geon-Ho
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.43-46
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    • 2001
  • The DC dielectric breakdown of epoxy composites used for transformer was experimented and then its data were simulated by Weibull distribution equation in this study. The more hardener increased the stronger breakdown strength at low temperature because of cross-linked density by the virtue of ester radical, and the breakdown strength of specimens with filler was lower than it of non-filler specimens because it was believed that the adding filler formed interface, charges were accumulated in it, the molecular mobility was raised, the electric field was concentrated, electrons were accelerated and then electron avalanche was early accomplished. From the analysis of Wei bull distribution equation, it was confirmed that as the allowed breakdown probability was· given by 0.1[%], the value of 'applied field was needed to be under 17.20[kV/mm].

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An Estimation of Life Time in Epoxy composites using Weibull Distribution Equation (와이블 분포식을 이용한 에폭시 복합체의 수명 시간 예측)

  • 신철기;김진사;정일형;임장섭;김태성;이준웅
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.11 no.3
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    • pp.167-173
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    • 1998
  • In order to estimate the life time of epoxy composites used for modeling material of transformer, the AC breakdown experiments of it were experimented and then the AC breakdown data were also simulated by Weibull distribution equation in this study. The life time of H100F65 specimen was the shortest and it of SH100F65 specimen was the longest, and as the AC voltage was applied to specimen for 50[min], the breakdown probability of each specimen was 31.2[%], 17.00[%], 84.36[%] and 12.35[%], respectively.

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Fabrication and Electromagnetic Characteristics of Multi-walled Carbon nanotube/Epoxy Composites (다중벽 나노튜브/에폭시 복합재의 제작과 전자기적 특성)

  • 이상의;박기연;이원준;김천곤;한재흥
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.107-110
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    • 2003
  • The electromagnetic intereference(EMI) shielding is very essential for commercial and military purposes. We fabricated multi-walled carbon nanoube(MWNT)/epoxy composites and studied the electromagnetic characteristics of the composites before we study the characteristics of MWNT-filled glass fiber-reinforced composites. After setting up the fabrication process, we measured the permittivities of MWNT/epoxy composites with process variables and MWNT concentrations in X-band(8.2GHz- 12.4GHz). Process variables changed the degree of dispersion, which influenced permittivities and permittivities increased rapidly from 0.5wt% to 1.0wt%.

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