• Title, Summary, Keyword: Composites

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Effect of Silicon Infiltration on the Mechanical Properties of 2D Cross-ply Carbon-Carbon Composites

  • Dhakate, S.R.;Aoki, T.;Ogasawara, T.
    • Carbon letters
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    • v.5 no.3
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    • pp.108-112
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    • 2004
  • Effect of silicon infiltration on the bend and tensile strength of 2D cross-ply carbon-carbon composites are studied. It is observed that bend strength higher than tensile strength in both types of composite is due to the different mode of fracture and loading direction. After silicon infiltrations bend and tensile strength suddenly decreases of carbon-carbon composites. This is due to the fact that, after silicon infiltration, silicon in the immediate vicinity of carbon forms the strong bond between carbon and silicon by formation silicon carbide and un-reacted silicon as free silicon. Therefore, these composites consist of three components carbon, silicon carbide and silicon. Due to mismatch between these three components secondary cracks developed and these cracks propagate from $90^{\circ}$ oriented plies to $0^{\circ}$ oriented plies by damaging the fibers (i.e., in-situ fiber damages). Hence, secondary cracks and in-situ fiber damages are responsible for degradation of mechanical properties of carbon-carbon composites after silicon infiltration which is revealed by microstructure investigation study by scanning electron microscope.

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Mechanical Properties of Carbon/Carbon Composites Densified by HIP Technique

  • Manocha, L.M.;Warrier, Ashish;Manocha, S.;Banerji, S.;Sathiyamoorthy, D.
    • Carbon letters
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    • v.6 no.1
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    • pp.6-14
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    • 2005
  • The study of mechanical properties and fracture behaviour of carbon/carbon composites is significant to its application and development. These are dependent on microstructure and properties of reinforcing fibers and matrix, fiber/matrix interface and porosity/cracks present in the composites. In the present studies high-density carbon/carbon composites have been prepared using PAN and various pitch based carbon fibers as reinforcements and pitch as matrix with repeated densification cycles using high-pressure impregnation and carbonization technique. Scanning electron microscopy has been used to study the fracture behaviour of the highly dense composites and correlated with structure of the composites. The geometry of reinforcement and presence of unfilled voids/cracks was found to influence the path of crack propagation and thereby the strength of composites. The type of stresses (tensile or compressive) accumulated also plays an important role in fracture of composites.

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Formaldehyde Emissions and Moisture Content Change of Wood Composites during Bake-out

  • Lee, Young-Kyu;Kim, Hyun-Joong
    • Journal of the Korean Wood Science and Technology
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    • v.40 no.2
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    • pp.101-109
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    • 2012
  • Wood composites are a hygroscopic material and have ability to exchange its moisture content with air. This study investigated the formaldehyde emission and moisture content change of four wood composites (particleboard (PB), medium density fiberboard (MDF), high density fiberboard (HDF), laminated HDF (L-HDF)) as a function of bake-out temperature and time. The composites were baked out for 1, 3, 5, 7, 10, 14, 21, and 28 days at temperatures of $20{\pm}2$, $35{\pm}2$, and $50{\pm}2^{\circ}C$ in a dry oven. The moisture content change was used to determine the emission bake-out of the composites. Best bake-out time results were obtained with after 7 days all composites. Formaldehyde emission values of composites decreased with decreasing moisture content for both temperatures. The formaldehyde emission results of bake-out temperature 35 and $50^{\circ}C$ showed a similar tendency.

A Study on the Partial Discharge Resistance Properties of Epoxy/Micro/Nano Alumina Composites (에폭시/마이크로/나노알루미나 콤포지트의 부분방전 저항성특성)

  • Park, Jae-Jun
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.65 no.6
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    • pp.1026-1031
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    • 2016
  • Neat Epoxy, nano alumina composites, micro alumina composites and multi-nano alumina composites were prepared and experiment were performed to measure their partial discharge resistant characteristics. The partial discharge resistance obtained for the microcomposites, nanocomposites and multi-nanocomposites are compared with those of unfilled epoxy and with GDE amount for surface modifier. It was observed that compare multi-nano alumina composites to micro alumina composites, the partial discharge resistance to degradation gets improved considerably. The improvement in the degradation resistance is attributed to the interface intension between the nano alumina composites and GDE, micro alumina and epoxy neat.

Fabrication of Ceramic Particulate Reinforced Steel Composites by Liquid Pressing Infiltration Process (용융가압함침공정을 이용한 세라믹 입자 강화 철강복합재료의 제조성 검증)

  • Cho, Seungchan;Lee, Yeong-Hwan;Ko, Seongmin;Park, Hyeon Jae;Lee, Donghyun;Shin, Sangmin;Jo, Ilguk;Lee, Sang-Kwan;Lee, Sang-Bok
    • Composites Research
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    • v.31 no.4
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    • pp.117-121
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    • 2018
  • Various ceramic particulate such as TiC, $TiB_2$, $Al_2O_3$ reinforced SUS431 matrix composites were successfully fabricated by a novel liquid pressing infiltration process. Microstructures of the SUS431 composite were analyzed to determine manufacturability of composites. $Al_2O_3$-SUS431 composite had lots of defects due to poor wettability between the $Al_2O_3$ and steel matrix. On the other hand, TiC was uniformly dispersed in the SUS431 matrix than $TiB_2$ and $Al_2O_3$ due to good wettability and interfacial properties.

Matrix Resin Systems with Different Molar Ratios to Improve the Properties of Fiber-reinforced Composites (섬유강화 복합재료의 물성향상을 위한 몰비가 다른 매트릭스 수지에 관한 연구)

  • 이상효;이장우
    • Polymer Korea
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    • v.24 no.4
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    • pp.459-468
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    • 2000
  • To improve the mechanical properties of fiber-reinforced polymer matrix composites, laminated composites plates were fabricated using different matrix resins and glass or aramid fibers. The effect of matrix resin system were evaluated by tensile, flexural strength measurements. In the case of surface treated aramid fiber and unsaturated polyester resin composite, maximum flexural properties were observed in the composite prepared from the glass fiber treated with 0.5 wt% silane coupling agents. Vinylester resin composites show the highest tensile properties and isophthalic polyester composites have the highest flexural properties among the unsaturated polyester resin composites studied. The relationship between overlap laminated composites plates and mechanical properties of polymer composites is also investigated in order to improve mechanical properties of glass fiber and unsaturated polyester resin composites.

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Effect of Hot Extrusion on the Mechanical Properties of 6061 Aluminum Alloy composites Reinforced with SiC whisker (SiC휘스커로 강화한 6061 Al합금 복합재료의 기계적 특성에 미치는 열간압출의 영향)

  • Kim, Jun-Su;Lim, Su-Geun
    • Journal of Korea Foundry Society
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    • v.16 no.2
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    • pp.132-140
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    • 1996
  • Both cast and extruded composites of SiC whisker reinforced 6061 Al alloy matrix were fabricated by high pressure infiltration of the alloy melt into the SiC preform and subsequent hot extrusion of the composite ingots. The micro structures, age hardening behavior and mechanical properties have been examined on the both cast and extruded composites of SiCw/6061. The cast composites of SiCw/6061 were obtained in which SiC whiskers were randomly oriented. Hot extrusion of these cast composites lead to alignment of the whisker in the direction of extrusion. Strengthening effect of whisker in the extruded composites is lower than that of the cast composites. The cast composites of SiCw/6061 showed higher thensile strength and lower elongation than extruded composites of SiCw/6061 at all testing temperatures. Lower tensile strength and higher elongation of the extruded composites were attributable to fine grain structures in which grain boundary sliding occruued preferentially at elevated temperatures.

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Thermotropic Liquid Crystal Polymer Reinforced Poly(butylene terephthalate) Composites to Improve Heat Distortion Temperature and Mechanical Properties

  • Kim, Jun-Young;Kang, Seong-Wook;Kim, Seong-Hun
    • Fibers and Polymers
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    • v.7 no.4
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    • pp.358-366
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    • 2006
  • Thermotropic liquid crystal polymer (TLCP)-reinforced poly(butylene terephthalate) (PBT) composites were prepared by melt processing. The improvement in the mechanical properties and the processability of the PBT/TLCP composites was attributed to the reinforcing effect by TLCP phase and its well distribution in the PBT matrix. X-ray diffraction results demonstrated that a slow cooling process leads to the thicker lamellar structures and the formation of more regular crystallites in the composites. The incorporation of TLCP improves not only the tensile strength and flexural modulus but also the heat distortion temperature (HDT) of the PBT/TLCP composites. The HDT values of the composites were dependent on TLCP content. The improvement in the HDT values of the PBT/TLCP composites may be explained in terms with the increased flexural modulus, the development of more regular crystalline structures, and the enhancement of the ability of the composites to sustain the storage modulus by TLCP phase. In addition, the simple additivity rule makes it possible to predict the HDT values of the PBT/TLCP composites.

A Novel Synthesis and Photonic Effect of Fe-CNT/TiO2 Composites by Controlling of Carbon Nanotube Amounts

  • Zhang, Kan;Meng, Ze-Da;Oh, Won-Chun
    • Korean Journal of Materials Research
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    • v.20 no.3
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    • pp.117-124
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    • 2010
  • Titanium dioxide ($TiO_2$) particles deposited on different quantitative Fe-treated carbon nanotube (CNT) composites with high photocatalytic activity of visible light were prepared by a modified sol-gel method using TNB as a titanium source. The composites were characterized by BET, XRD, SEM, TEM and EDX, which showed that the BET surface area was related to the adsorption capacity for each composite. From TEM images, surface and structural characterization of for the CNT surface had been carried out. The XRD results showed that the Fe-ACF/$TiO_2$ composite mostly contained an anatase structure with a Fe-mediated compound. EDX results showed the presence of C, O, and Ti with Fe peaks in the Fe-CNT/$TiO_2$ composites. The photocatalytic activity of the composites was examined by degradation of methylene blue (MB) in aqueous solution under visible light, which was found to depend on the amount of CNT. The highest photocatalytic activity among the different composites was related to the optimal content of CNT in the Fe-CNT/$TiO_2$ composites. In particular, the photocatalytic activity of the Fe-CNT/$TiO_2$ composites under visible light was better than that of the CNT/$TiO_2$ composites due to the introduction of Fe particles.