• Title/Summary/Keyword: Epoxy composites

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The Properties of Degradation in Epoxy Composites according to Electrical Stress

  • Park, Young-Chull;Park, Geon-Ho
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.47-51
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    • 2001
  • The electrical degradation phenomena of epoxy composites to be used as a molding material for transformers were studied. The electrets were first manufactured by applying high voltages to five kinds of specimens given a mixing rate, and then TSC(Thermally Stimulated Current) values at the temperature range of $-160\sim200[^{\circ}C]$ were measured from a series of experiments. The behaviour of carrier and its origin in epoxy composites were examined, respectively, And various effects of electrical degradation on epoxy composites were also discussed in this study.

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Effect of Surfactant Addition on the Dielectric Properties of BaTiO3/epoxy Composites (분산제가 BaTiO3/에폭시 복합체의 유전특성에 미치는 영향)

  • Lee, Dong-Ho;Kim, Byung-Kook;Je, Hae-June
    • Korean Journal of Materials Research
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    • v.19 no.11
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    • pp.576-580
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    • 2009
  • $BaTiO_3$/epoxy composites have been widely investigated as promising materials for embedded capacitors in printed circuit boards. It is generally known that the dielectric constant (K) of the $BaTiO_3$/epoxy composites increases with improvement of the dispersion of $BaTiO_3$ particles in the epoxy matrix that comes from adding surfactant. The influences of surfactant addition on the dielectric properties of the $BaTiO_3$/epoxy composites are reported in the present study. The dielectric constant of the $BaTiO_3$/epoxy composites is not significantly affected by the surfactant addition. However, the temperature coefficient of capacitance increases and the peel strength decreases as the amount of added surfactant increases. The influences of surfactant addition on the dielectric properties of the neat epoxy are also very similar to those of the $BaTiO_3$/epoxy composites. The residual surfactant in the $BaTiO_3$/epoxy composites affects the temperature coefficient of capacitance and the peel strength of the epoxy matrix, which in turn affects the temperature coefficient of capacitance and the peel strength of the $BaTiO_3$/epoxy composites.

Effect of Degree of Particle Agglomeration on the Dielectric Properties of BaTiO3/Epoxy Composites (분말 응집도가 BaTiO3/에폭시 복합체의 유전특성에 미치는 영향)

  • Han, Jeong-Woo;Kim, Byung-Kook;Je, Hae-June
    • Korean Journal of Materials Research
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    • v.18 no.10
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    • pp.542-546
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    • 2008
  • $BaTiO_3$/epoxy composites can be applied as the dielectric materials for embedded capacitors. The effects of the degree of $BaTiO_3$ particle agglomeration on the dielectric properties of $BaTiO_3$/epoxy composites were investigated in the present study. The degree of particle agglomeration was controlled by the milling of the agglomerated particles. The size and content of the agglomerated $BaTiO_3$ particles decreased with an increase in the milling time. The dielectric constants and polarizations of $BaTiO_3$/epoxy composites abruptly decreased with the increase of the milling time. It was concluded that the dielectric constants and polarizations of $BaTiO_3$/epoxy composites decreased as the degree of particle agglomeration decreased. The degree of agglomeration of $BaTiO_3$ particles turned out to be a very influential factor on the dielectric properties of $BaTiO_3$/epoxy composites.

Effect of Moisture Absorption on the Flexural Properties of Basalt/CNT/Epoxy Composites

  • Kim, Man-Tae;Rhee, Kyong-Yop;Kim, Hyeon-Ju;Jung, Dong-Ho
    • Carbon letters
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    • v.13 no.3
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    • pp.187-189
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    • 2012
  • This study investigates the flexural properties of multi-walled carbon nanotube (MWCNT) reinforced basalt/epoxy composites under conditions with and without moisture absorption. The basalt/CNT/epoxy composites were fabricated using 1 wt% silanized MWCNTs and kept in seawater for over 4 months. The flexural properties of the moisture absorbed specimens were evaluated and compared with those of dry specimens. The flexural properties of basalt/CNT/epoxy composites were found to decrease with moisture absorption. The flexural strength and modulus of moisture absorbed specimens were 22% and 16% lower, respectively, than those of the dry specimen. Scanning electron microscope examination of the fracture surfaces revealed that the decreases of flexural properties in the moisture absorbed specimen were due to the weakening of interfacial bonding from swelling of the epoxy matrix.

The Characteristics of Degradation in Epoxy Composites for Molding Materials of PT (변성기의 몰딩 재료용 에폭시복합체의 열화 특성)

  • Park, Geon-Ho
    • Proceedings of the Korean Society of Computer Information Conference
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    • pp.351-354
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    • 2011
  • The electrical degradation phenomena of epoxy composites to be used as a molding material for transformers were studied. The electrets were first manufactured by applying high voltages to five kinds of specimens given a mixing rate, and then TSC(Thermally Stimulated Current) values at the temperature range of $-160{\sim}200[^{\circ}C]$ were measured from a series of experiments. The behaviour of carrier and its origin in epoxy composites were examined, respectively. And various effects of electrical degradation on epoxy composites were also discussed in this study.

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Effect of Plasma Modification of Woven type Carbon Fibers on the Wear Behavior of Carbon Fiber/Epoxy Composites (평직 탄소섬유의 플라즈마 처리 및 이에 따른 탄소섬유/에폭시 복합재의 마모 특성)

  • Lee, Jae-Seok;Rhee, Kyong-Yop
    • Journal of the Korean Society for Precision Engineering
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    • v.27 no.12
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    • pp.113-118
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    • 2010
  • For a present study, woven type carbon fibers were surface-modified by oxygen plasma to improve adhesive strength between carbon fibers and epoxy. The change of hydrophilic properties by the plasma modification was investigated through the contact angle measurement and the calculation of surface energy of carbon fiber due to the oxygen plasma modification. FESEM and XPS analyses were performed to study the chemical and physical changes on the surface of carbon fibers due to the oxygen plasma modification. Pin-on-disk wear tests were conducted under dry condition using unmodified and plasma-modified carbon/epoxy composites to investigate the effect of plasma modification on the wear behavior of woven type carbon/epoxy composites. The results showed that the friction coefficient and the wear rate of plasma-modified carbon/epoxy composites were lower than those of unmodified carbon/epoxy composites, respectively. XPS analysis showed that new functional group of a carbonyl type was created on the carbon fibers by the $O_2$ plasma treatment, which enhanced adhesive strength between carbon fibers and epoxy, leading to improve wear properties

Development of Elastic Composites Using Waste Tire Chip and Epoxy Resin - Focused on Strength and Durability - (폐타이어 칩 및 에폭시를 활용한 탄성 복합체의 개발 - 강도와 내구성을 중심으로 -)

  • Sung, Chan Yong;Noh, Jin Yong
    • Journal of The Korean Society of Agricultural Engineers
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    • v.58 no.1
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    • pp.19-26
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    • 2016
  • This study was performed to evaluate the strength and durability properties of modified epoxy composites with waste tire chip, recycled coarse aggregate, filler and modified epoxy to improve elongation and elasticity of epoxy. Additionally, for comparing to modified epoxy and unsaturated polyester resin as a binder, unsaturated polyester resin composites were developed in the same condition. The mix proportions were determined to satisfy the requirement for the workability and slump according to aggregate size and binder content. Tests for the compressive and flexural strength, freezing and thawing and durability for 20 % sulfuric solution were performed. The compressive and flexural strength of modified epoxy composites were in the range of 34.9~61.6 MPa and 10.2~18.3 MPa at the curing 7 days, respectively. Also, the compressive and flexural strength of unsaturated polyester resin composites were in the range of 44.2~77.8 MPa and 11.3~20.8 MPa at the curing 7 days, respectively. After 300 cycles of freezing and thawing, weight decrease ratio and durability factor of modified epoxy composites were in the range of 0.8~1.9 % and 95~98, respectively. Accordingly, modified epoxy composites will greatly improve the durability of concrete.

TSC characteristics according to curing time and corona degradation in epoxy composites (경화시간 및 코로나 열화에 따른 에폭시 복합체의 열자격 전류특성)

  • 박건호;김영천;황석영;이준웅
    • Electrical & Electronic Materials
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    • v.8 no.6
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    • pp.759-767
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    • 1995
  • This paper examines the electrical properties according to a curing time and a corona degradation in epoxy composites which are used for transformers. To consider these phenomena, the electrets were formed by appling high voltages to five kinds of specimens designed according to a constant mixing rate and then TSC(Thermally Stimulated Current) values at the temperature range of -160-200[>$^{\circ}C$] were measured from a series of experiments. The behaviour of carrier and its possible origins in epoxy composites were studied. Various effects of curing time and electric field on epoxy composites were also investigated.

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Fatigue modeling of chopped strand mat/epoxy composites

  • Shokrieh, M.M.;Esmkhania, M.;Taheri-Behrooz, F.
    • Structural Engineering and Mechanics
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    • v.50 no.2
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    • pp.231-240
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    • 2014
  • In the present research, fatigue behavior of chopped strand mat/epoxy composites has been studied with two different techniques. First, the normalized stiffness degradation approach as a well-known model for unidirectional and laminated composites was utilized to predict the fatigue behavior of chopped strand mat/epoxy composites. Then, the capability of the fatigue damage accumulation model for chopped strand mat/epoxy composites was investigated. A series of tests has been performed at different stress levels to evaluate both models with the obtained results. The results of evaluation indicate a better correlation of the normalized stiffness degradation technique with experimental results in comparison with the fatigue damage accumulation model.

A Study on the Prepreg Treatment to Improve Interlaminar Fracture Behavior of Graphite/Epoxy Composites (Graphite/Epoxy 적층복합재의 층간파괴 향상을 위한 프리프레그의 전처리 연구)

  • Kim, Min-Ho;Rhee, Kyong-Yop;Paik, Young-Nam;Kim, Hyeon-Ju;Jung, Dong-Ho
    • Journal of the Korean Society for Precision Engineering
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    • v.23 no.10
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    • pp.68-73
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    • 2006
  • In this study, the graphite/epoxy prepregs were surface-treated using oxygen plasma, and optimal treatment time was determined measuring the contact angle on the prepreg surface. Interlaminar fracture behavior of surface-treated graphite/epoxy composites was compared with that of regular (untreated) graphite/epoxy composites. The results showed that the contact angle was a minimum when treated for 30 minutes. The interlaminar fracture toughness of surface-treated specimen was improved about 15% compared with that of regular specimen.