• Title/Summary/Keyword: COMPOSITES

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Technical Review on the Design Methods and Guidelines for fiber Reinforced Composites (건축토목용 복합재료의 국내.외 설계기준 분석)

  • Han, Bog-Kyu;Hong, Geon-Ho;Kim, Ki-Soo
    • Composites Research
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    • v.19 no.4
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    • pp.39-43
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    • 2006
  • A decade ago, the technology of strengthening structures using FRP composites was primitive, with very few publications. Nowadays, the potential growth of research is achieved to the wide recognition of the importance of this new technology. In fact, significant practical applications have been preceded and the development of design methods have been achieved. However, the specific design methods for each applications are still lack of design skills in spite of the wide applications of FRP composites in the construction industry. The purpose of this paper is to report the development of design methods for FRP-strengthened structures by technical review design methods and guidelines of fiber reinforced composites.

Application Technologies of Fiber Reinforced Composites on the Building Structure (섬유복합재료(FRP)의 건설 적용 사례 연구 (건축편))

  • Han Bog-Kyu;Kwon Young-Jin;Park Sung-Woo;Hong Geon-Ho
    • Composites Research
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    • v.19 no.3
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    • pp.37-42
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    • 2006
  • In the past, the technology of strengthening structures using FRP composites was still in its infancy, with very few publications on the technology available. However, recently strengthening of Reinforced concrete (RC) and other structures using advanced fibre-reinforced polymer/plastic(FRP) composites has become very popular in the last few years. As the well-known advantages of FRP composites including both good corrosion resistence and ease for site handling due to their light weight, also its design methods have been ensured the safe and economic use of this new technology, FRPs have been used widely and demonstrated in the field of aero industries etc. The purpose of this paper is to report the examples of the many diverse applications of Fiber Reinforced Plastic in construction materials of structures.

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.

Mechanical and Electrical Properties of Hot-Pressed Silicon Carbide-Zirconium Diboride Composites (고온가압소결한 SiC-ZrB$_2$ 복합체의 기계적, 전기적 특성)

  • 신용덕
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 1997.04a
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    • pp.135-140
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    • 1997
  • The influences of ZrB$_2$ additions to SiC on microstructural, DDM(Electrical Discharge Machining), mechanical and electrical properties were investigated. composites were prepared by adding 15, 30, 45 vol.% ZrB$_2$particles as a second phase to SiC matrix. SiC-ZrB$_2$ composites obtained by hot pressing for high temperature structural application were fully dense with the relative densities over 99%. The fracture toughness of the composites were increased with the ZrB$_2$contents. In case of composite containing 30vol.% ZrB$_2$, the flexural strength and fracture toughness showed 45% and 60% increase, respectively compared to that of monolithic SiC sample. The electrical resistivities of SiC-ZrB$_2$ composites decreased significantly with the ZrB$_2$ contents. The electrical resistivity of SiC-30vol.% ZrB$_2$ composite showed 6.50$\times$10$^{-4}$ $\Omega$.cm. Cutting velocity of EDM of SiC-ZrB$_2$ composites are directly proportional to duty factor of pulse width. Surface roughness, however, are not all proportional to pulse width. Higher-flexural strength composites show a trend toward smaller crater volumes, leaving a smoother surface; the average surface roughness of the SiC-ZrB$_2$ 15 vol.% composite with the flexural strengthe of 375㎫ was 3.2${\mu}{\textrm}{m}$, whereas the SiC-ZrB$_2$ 30.vol% composite of 457㎫ was 1.35${\mu}{\textrm}{m}$. In the SEM micrographs of the fracture surface of SiC-ZrB$_2$ composites, the SiC-ZrB$_2$ two phases are distinct; the white phase is the ZrB$_2$and the gray phase is the SiC matrix. In the SEM micrographs of the EDM surface, however, these phases are no longer distinct because of thicker recast layer of resolidified-melt-formation droplets present. It is shown that SiC-ZrB$_2$ composites are able to be machined without surface cracking.

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Influence of Oxidation Inhibitor on Carbon-Carbon Composites : 7. Studies on Work of Adhesion and Fracture Toughness of Carbon-Carbon Composites (산화억제제를 첨가한 탄소/탄소 복합재료의 물성에 관한 연구 : 7. 탄소/탄소 복합재료외 부착력과 파괴인성)

  • 박수진;서민강;이재락
    • Polymer(Korea)
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    • v.25 no.3
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    • pp.435-440
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    • 2001
  • The objective of this study was to examine the effect of oxidation inhibitor contents on the work of adhesion, fracture toughness, and impact strength of the unidirectional carbon-carbon composites (C/C composites). The molybdenum disilicide ($MoSi_2$) used as an oxidation inhibitor was impregnated with phenolic resins to improve the anti-oxidation properties of the composites in different concentrations of 4, 12 and 20 wt%. Based on Wilhelmy equation, the work of adhesion of C/C composites was calculated by contact angle methods. Fracture toughness and impact strength were pressured by three-point bending test for the critical intensity factor ($K_IC$) and Izod test method, respectively. As a result, the composites made with $MoSi_2$ resulted in an increasing of both fracture toughness and impact strength. Especially, the composites made with 12 wt% $MoSi_2$ content showed the highest value of London dispersive component, $W_A\;^L$, in work of adhesion, resulting from improving the interfacial adhesion force among fibers, filler, and matrix in this system.

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Property improvement of natural fiber-reinforced green composites by water treatment

  • Cho, Dong-Hwan;Seo, Jeong-Min;Lee, Hyun-Seok;Cho, Chae-Wook;Han, Seong-Ok;Park, Won-Ho
    • Advanced Composite Materials
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    • v.16 no.4
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    • pp.299-314
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    • 2007
  • In the present study, natural fibers (jute, kenaf and henequen) reinforced thermoplastic (poly(lactic acid) and polypropylene) and thermosetting (unsaturated polyester) matrix composites were well fabricated by a compression molding technique using all chopped natural fibers of about 10 mm long, respectively. Prior to green composite fabrication, natural fiber bundles were surface-treated with tap water by static soaking and dynamic ultrasonication methods, respectively. The interfacial shear strength, flexural properties, and dynamic mechanical properties of each green composite system were investigated by means of single fiber microbonding test, 3-point flexural test, and dynamic mechanical analysis, respectively. The result indicated that the properties of the polymeric resins were significantly improved by incorporating the natural fibers into the resin matrix and also the properties of untreated green composites were further improved by the water treatment done to the natural fibers used. Also, the property improvement of natural fiber-reinforced green composites strongly depended on the treatment method. The interfacial and mechanical results agreed with each other.

Development of 3D Woven Preform π-beam based on T-beam Made of Laminated Composites (적층복합재료 T-빔 기반의 3차원 직조 프리폼 π-빔 개발)

  • Park, Geon-Tae;Lee, Dong-Woo;Byun, Joon-hyung;Song, Jung-il
    • Composites Research
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    • v.33 no.3
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    • pp.115-124
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    • 2020
  • Laminate composites, especially Carbon fiber-reinforced composites are wide used in various industry such as aerospace and automotive industry due to their high specific strength and specific stiffness. However, the laminate composites has a big disadvantage that delamination occurs because the arrangement of the fibers is all arranged in the in-plane direction, which limits the field of application of the laminate composites. In this study, we first developed a laminate composites T-beam in which π-beam and flat plate were combined and optimized the design parameters through structural analysis and mechanical tests. Afterwards, 3D weave preform T-beam was developed by applying the same design parameters of laminate composites T-beams, and improved mechanical strength was achieved compared to laminated structures. These findings are expected to be applicable to existing laminated composite structures that require increased strength.

An Experimental Study on the Mechanical Properties of Fiber Reinforced Fly Ash.Lime.Gypsum Composites (섬유보강 플라이애쉬.석고.복합체의 역학적특성에 관한 실험적 연구)

  • 박승범
    • Magazine of the Korea Concrete Institute
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    • v.5 no.4
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    • pp.145-155
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    • 1993
  • The results of an experimental study on the manufacture and the mechanical properties of fiber reinforced fly ash$\cdot$lime$\cdot$gypsum composites are presented in this paper. 'The composites using fly ash, lime, and gypsum were prepared with various fibers (PAN-derived and Pitch-derived carbon fiber, alkali-resistance glass fiber) and a small amount of polymer emulsion-styrene butadiene rubber latex (SBR). As the test results show, the manufacturing process technology of fly ash$\cdot$lime$\cdot$gypsum composites was developed and its optimum mix proportions were successfully proposed. And the flexural strength and toughness of fiber reinforced fly ash$\cdot$lime $\cdot$gypsum composites were increased remarkably by fiber contents, but the compressive strength of the composites were influenced by the kinds fiber more than by the fiber contents. Also, the addition of a polymer emulsion to the composites decreased the bulk specific gravity, but the compressive and flexural strength, and the toughness of the composites were not influenced by it, but were considerably improved by increasing fiber contents.

Electrical Properties of Nanostructured Carbon Black-filled HDPE Composites: Effect of Electron Beam Irradiation on PTC Characteristics (나노구조 카본블랙/HDPE 복합재료의 전기적 특성: 전자선 조사에 의한 PTC 특성변화)

  • 박수진;송수완;서민강;이재락
    • Composites Research
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    • v.16 no.1
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    • pp.19-25
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    • 2003
  • In this paper, electrical properties of nanostructured carbon blacks (CB)-filled high density polyethylene (HDPE) composites were investigated as a function of temperature, which were prepared by the conventional melt-mixing method. The composites were irradiated with electron beam in a dosage of 30∼150 kGy to enhance an electronical reproducibility and to reduce a negative temperature coefficient (NTC) phenomenon. And, gel contents (%) of irradiated CB/HDPE composites were estimated by solvent extraction method. From the experimental results. the positive temperature coefficient (PTC) intensity of the composites was strongly depended on the CB content and particle size. And, the increase of gel contents (%) and disappearance of NTC behavior of the composites were identified at a dosage of 60 kGy. It was also found that the electron beam irradiation made an improvement of electrical reproducibility of the composites. This result was probably due to the reduction of the freedom of CB movement at above the melting temperature of the polymer crystalline, resulting in increasing the crosslinking structure of the composites.