• Title/Summary/Keyword: Epoxy composites

Search Result 386, Processing Time 0.11 seconds

Mixed Mode Interlaminar Fracture Behaviors of Carbon Fabric/Epoxy Composites (탄소섬유직물/에폭시 복합재의 혼합모우드 층간파괴 거동)

  • Yoon, Sung-Ho;Heo, Kwang-Soo;Oh, Jin-Oh
    • Journal of the Korean Society for Aeronautical & Space Sciences
    • /
    • v.35 no.1
    • /
    • pp.58-65
    • /
    • 2007
  • Mixed mode interlaminar fracture behaviors of carbon fabric/epoxy composites were investigated through MMF (Mixed Mode Flexural) test by varying mixed mode ratio ranging from 20% to 90%. Mixed mode interlaminar fracture criteria based on NL point and 5% offset point were also suggested in order to predict mixed mode interlaminar fracture behaviors. Fracture surfaces and crack propagating behaviors were examined through a travelling scope and a scanning electron microscope. According to the results, mixed mode interlaminar fracture behaviors can be predicted by mixed mode interlaminar fracture criterion with m=1.5 and n=0.5 on the basis of NL point or mixed mode interlaminar fracture criterion with m=2 and n=3 on the basis of 5% offset point. Fracture surfaces and crack propagating behaviors are sensitive to mixed mode ratios. MMF test can be successfully applicable in evaluating mixed mode interlaminar fracture toughness of carbon fabric/epoxy composites.

Analysis of DC insulation and properties of epoxy/ceramic composites with nanosized ZnO/TiO2 fillers

  • Kwon, Jung-Hun;Kim, Yu-Min;Kang, Seong-Hwa;Kim, Pyung-Jung;Jung, Jong-Hoon;Lim, Kee-Joe
    • Journal of Ceramic Processing Research
    • /
    • v.13 no.spc2
    • /
    • pp.332-335
    • /
    • 2012
  • A molded transformer is maintenance-free, which makes it unnecessary to replace the insulating material, like in an oil-filled transformer, because the epoxy, which is a molded insulating resin, does not suffer variations in its insulating performance for heat cycles over a long time, as compared to insulating oil. In spite of these advantages, a molded transformer may still be accessed by the user, which is not good in regards to reliability or noise compared to the oil transformers. In particular, a distrust exists regarding reliability due to the long-term insulating performance. These properties have been studied in regards to the improvement of epoxy composites and molded transformer insulation. There have nevertheless been insufficient investigations into the insulation properties of epoxy composites. In this study, it is a researching of the epoxy for insulating material. In order to prepare the specimens, a main resin, a hardener, an accelerator, and a nano/micro filler were used. Varying amounts of TiO2 and ZnO nano fillers were added to the epoxy mixture along with a fixed amount of micro silica. This paper presents the DC insulation breakdown test, thermal expansion coefficient, and thermal conductivity results for the manufactured specimens. From these results, it has been found that the insulating performance of nano/micro epoxy composites is improved as compared to plain molded transformer insulation, and that nano/micro epoxy composites contribute to the reliability and compactness of molded transformers.

Mechanical Properties of Jute Fiber Reinforced Thermosetting Composites (황마섬유 보강 열경화성 복합재료의 기계적 특성)

  • Lee, C.H.;Song, J.E.;Nam, W.S.;Byun, J.H.;Kim, B.S.;Hwang, B.S.
    • Proceedings of the Korean Society For Composite Materials Conference
    • /
    • /
    • pp.111-115
    • /
    • 2005
  • Recently, natural fibers draw much interests in composite industry due to low cost, light weight, and environment-friendly characteristics compared with glass fibers. In this study, mechanical properties were evaluated for two extreme cases of jute fiber orientations, i.e. the unidirectional yarn composites and the felt fabric composites. Samples of jute fiber composites were fabricated by RTM process using epoxy resin, and tensile, compression, and shear tests were conducted. As can be expected, unidirectional fiber specimens in longitudinal direction showed the highest strength and modulus. Compared with glass/epoxy composites of the similar fabric architecture and fiber volume fraction, the tensile strength and modulus of jute felt/epoxy composites reached only 40% and 50% levels. However, the specific tensile strength and modulus increased to 80% and 90% of the glass/epoxy composites. The main reason for the poor mechanical properties of jute composites is associated with the weak interfacial bonding between fiber and matrix. The effect of surface treatment of jute fibers on the interfacial bonding will be examined in the future work.

  • PDF

An investigation of tribology properties carbon nanotubes reinforced epoxy composites (표면 개질된 탄소나노튜브를 사용한 에폭시 복합재료의 마모특성에 관한 연구)

  • Sulong A.B.;Goak J.C.;Park Joo-Hyuk
    • Proceedings of the Korean Society of Precision Engineering Conference
    • /
    • /
    • pp.663-667
    • /
    • 2005
  • Surface modified carbon nanotubes were applied into the epoxy composites to investigate its tribological property. Carbon nanotubes reinforced epoxy composites were fabricated by casting. Effects to the tribological property of loading concentrations and types of surface modification of carbon nanotubes were investigated under sliding condition using linear reciprocal sliding wear tester. The results show that the small amount of carbon nanotubes into the epoxy exhibited lower weight loss than the pure epoxy. It is concluded that the effect of an enormous aspect ratio of carbon nanotubes surface area which wider than conventional fillers that react as interface for stress transfer. As increased the contents of carbon nanotubes, the weight loss from the wear test was reduced. And the surface modified carbon nanotubes show better tribological property than as produced carbon nanotubes. It is due that a surface modification of carbon nanotubes increases the interfacial bonding between carbon nanotubes and epoxy matrix through chemical bonding. Changes in worn surface morphology are also observed by optical microscope and SEM for investigating wear behaviors. Carbon nanotubes in the epoxy matrix near the surface are exposed, because it becomes the lubricating working film on the worn surface. It reduces the friction and results in the lower surface roughness morphology in the epoxy matrix as increasing the contents of the carbon nanotubes.

  • PDF

Mechanical properties of epoxy composites reinforced with ammonia-treated graphene oxides

  • Park, Mi-Seon;Lee, Sangmin;Lee, Young-Seak
    • Carbon letters
    • /
    • v.21
    • /
    • pp.1-7
    • /
    • 2017
  • The effects of ammonia-treated graphene oxide (GO) on composites based on epoxy resin were investigated. Ammonia solutions of different concentrations (14-28%) were used to modify GO. Nitrogen functional groups were introduced on the GO surfaces without significant structural changes. The ammonia-treated GO-based epoxy composites exhibited interesting changes in their mechanical properties related to the presence of nitrogen functional groups, particularly amine ($C-NH_2$) groups on the GO surfaces. The highest tensile and impact strength values were 42.1 MPa and 12.3 J/m, respectively, which were observed in an epoxy composite prepared with GO treated with a 28% ammonia solution. This improved tensile strength was 2.2 and 1.3 times higher than those of the neat epoxy and the non-treated GO-based epoxy composite, respectively. The amine groups on the GO ensure its participation in the cross-linking reaction of the epoxy resin under amine curing agent condition and enhance its interfacial bonding with the epoxy resin.

Effects of acid-anhydride hardener and postcuring heat-treatments on dielectric properties of epoxy composites (에폭시 복합체의 유전특성에 미치는 산무수물 경화제와 후경화 열처리의 영향)

  • 왕종배;이성일;이준웅
    • Electrical & Electronic Materials
    • /
    • v.7 no.3
    • /
    • pp.187-199
    • /
    • 1994
  • In order to find an effect of structural changes due to variation of addition ratio of anhydride hardener and postcuring herat-treatments upon electrical properties of epoxy composites, the dielectric properties over a frequency range from 30[Hz] to l[MHz] were investigated in the temperature range of 20-180[.deg. C]. From the dielectric properties, the a peaks related with glass-transition phenomena of epoxy network appeared near 130[.deg. C], the conduction loss in high temperature region above 150[.deg. C] due to thermal dissociation of hardener started off with the low frequency side and the .betha. peak concerned with contribution of movable unreacted terminal epoxy groups and curing agents in the glass states concurred with the high-frequency side below 20[.deg. C]. And an effect of an hydride hardener upon structural changes and of postcuring heat treatments upon structural stability in epoxy composites would be explained through the estimation of the distribution of relaxation times and the activation energy for a .alpha. peak according to the WLF equations.

  • PDF

Effect of Ceramic Powder Content and Shape on the Electrical Properties of Ceramic(BaTiO3)-polymer(Epoxy) Composite for Embedded Capacitors (임베디드 커패시터용 세라믹(BaTiO3)-고분자(에폭시) 필름의 세라믹 분말 형상 및 함량에 따른 전기적 특성)

  • Han, Jeong-Woo;Yoon, Jung-Rag;Je, Hae-June;Lee, Dong-Ho;Lee, Kyung-Min
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
    • /
    • v.22 no.6
    • /
    • pp.495-500
    • /
    • 2009
  • The ceramic($BaTiO_3$)-polymer(epoxy) composites have been widely investigated as dielectric materials for embedded capacitors in printed circuit boards (PCBs). The dielectric properties of $BaTiO_3$/epoxy composites prepared using the agglomerated $BaTiO_3$ particles were investigated in the present study. The dielectric constants of the composites prepared using the agglomerated $BaTiO_3$ particles were about 2 times higher than those of the composites with the dispersed $BaTiO_3$ particles. The insulation resistance of the composites prepared using the agglomerated $BaTiO_3$ particles were lower than those of the composites with dispersed $BaTiO_3$ particles. As a result, there is tradeoff between high dielectric constant and insulation resistance in the $BaTiO_3$/epoxy composites. So it is important to select proper agglomerated or dispersed $BaTiO_3$ particles in accordance with needs.

Dielectric Properties of Epoxy Composites with Varying Frequency (에폭시 복합체의 주파수 변화에 따른 유전특성)

  • Lee, Ho-Shik
    • Journal of the Korean Applied Science and Technology
    • /
    • v.35 no.3
    • /
    • pp.676-682
    • /
    • 2018
  • In order to study electrical properties of epoxy composites with various frequency. To measure of dielectric characteristics have been performed over a frequency range from 30[Hz] to 3[MHz] and a temperature range of $20[^{\circ}C]$, $100[^{\circ}C]$, $140[^{\circ}C]$. We observed values of dielectric constant and dissipation of the epoxy composites with various frequency. We were observed dielectric loss and dispersion in low frequency region. Also, we observed to decrease of the dielectric constant due to the effects of filler in high temperature region.

Stundy on Simulation Characteristics of Low Velocity Impact Test of Carbon/Epoxy Composite Plates Manufactured by Filament Winding Method (필라멘트 와인딩 공법으로 제작한 탄소섬유/에폭시 복합소재 평판의 저속 낙하 충격시험 시뮬레이션에 관한 연구)

  • BYUN, JONGIK;KIM, JONGLYUL;HEO, SEOKBONG;KIM, HANSANG
    • Transactions of the Korean hydrogen and new energy society
    • /
    • v.29 no.2
    • /
    • pp.190-196
    • /
    • 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.

A Study on Tensile Properties of Multi-Welled Carbon Nanotube/Epoxy Composites (다중벽 탄소나노튜브/에폭시 복합재료의 인장 물성에 관한 연구)

  • Lee Sang-Eui;Lee Won-Jun;Kim Chun-Gon
    • Composites Research
    • /
    • v.17 no.6
    • /
    • pp.1-7
    • /
    • 2004
  • The studies of particulate reinforced composites have been conducted for many years. The nanocomposites to be studied vigorously in recent years are one of them. We fabricated and studied multi-walled carbon nanotube(MWNT)/epoxy composites which may be useful as matrix for continuous fiber-reinforced composites. We investigated tensile properties of MWNT/epoxy composites as a function of MWNT concentration, which were prepared by the fabrication method established in this study. Tensile stiffness and strength increased 19% at 0.5 wt% and 12% at 0.2 wt%, respectively. We observed the reaggregation phenomenon of MWNTS during curing, which should be controlled to obtain higher tensile properties.