• Title/Summary/Keyword: Polymer specimen

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Seismic repair of captive-column damage with CFRPs in substandard RC frames

  • Tunaboyu, Onur;Avsar, Ozgur
    • Structural Engineering and Mechanics
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    • v.61 no.1
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    • pp.1-13
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    • 2017
  • The effectiveness of the repair scheme for the damaged captive-columns with CFRPs (Carbon Fiber Reinforced Polymer) was investigated in terms of response quantities such as strength, ductility, dissipated energy and stiffness degradation. Two 1/3 scale, one-story one-bay RC (Reinforced Concrete) frames were designed to represent the substandard RC buildings in Turkish building stock. The first one, which is the reference specimen, is the bare frame without infill wall. Partial infill wall with opening was constructed between the columns of the second frame and this caused captive column defect. Severe damage was observed with the concentration of shear cracks in the second specimen columns. Then, the damaged members were repaired by CFRP wrapping and retested. For the three test series, similar reversed cyclic lateral displacement under combined effect of axial load was applied to the top of the columns. Overall response of the bare frame was dominated by flexural cracks. Brittle type of shear failure in the column top ends was observed in the specimen with partial infill wall. It was observed that former capacity of damaged members of the second frame was recovered by the applied repair scheme. Moreover, ultimate displacement capacity of the damaged frame was improved considerably by CFRP wrapping.

Effect of Bonding Surface Laser Patterns on Interfacial Toughness of GFRP/Al Composite (GFRP/Al 복합재료의 접합부 레이저 패턴이 계면인성에 미치는 영향)

  • Woo Yong Sim;Yu Seong Yun;Oh Heon Kwon
    • Journal of the Korean Society of Safety
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    • v.38 no.2
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    • pp.1-7
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    • 2023
  • Fiber-metal laminates (FMLs) and polymer matrix composites (PMCs) are formed in various ways. In particular, FMLs in which aluminum is laminated as a reinforced layer are widely used. Also, glass fiber-reinforced plastics (GFRPs) are generally applied as fiber laminates. The bonding interface layer between the aluminum and fiber laminate exhibits low strength when subjected to hot press fabrication in the event of delamination fracture at the interface. This study presents a simple method for strengthening the interface bonding between the aluminum metal and GFRP layer of FML composites. The surfaces of the aluminum interface layer are engraved with three kinds of patterns by using the laser machine before the hot press works. Furthermore, the effect of the laser patterns on the interfacial toughness is investigated. The interfacial toughness was evaluated by the energy release rate (G) using an asymmetric double cantilever bending specimen (ADCB). From the experimental results, it was shown that the strip type pattern (STP) has the most proper pattern shape in GFRP/Al FML composites. Therefore, this will be considered a useful method for the safety assessment of FML composite structures.

Interfacial bonding Energy between Laser Surface Treated HA layer and Ti alloy (레이저 표면처리에 의한 수산화아파타이트 코팅된 타이타니움합금 경계면의 결합에너지)

  • Moon, D.S.;Kim, Y.K.;Nam, S.Y.;Cho, H.S.;Huh, E.J.;Kim, S.Y.;Lee, J.H.
    • Proceedings of the KOSOMBE Conference
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    • v.1997 no.05
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    • pp.35-38
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    • 1997
  • The interfacial bonding energy between laser surface treated HA layer and Ti alloy substrate was investigated using a mechanical push-out tester. The initial slope of shear-stress and reduced displacement curves, maximum interfacial bond strength and bonding energy were calculated from results of the push-out test. The calculated initial slpoes are 38 MPa for the Ti alloy(A), 65 MPa for the sandblast finished specimen(B), 95 MPa for the HA plasma spray coated specimen and 49 MPa for the laser surface treated specimen(D). The maximum interfacial bonding strength are 3 MPa for the A, 19 MPa for the B, 20 MPa for the C, 10 MPa for the D. The interfacial bonding energies are $3.3\times10^{-9}J/mm^2$ for the A, $15.5\times10^{-9}J/mm^2$ for the B, $15.6\times10^{-9}J/mm^2$ for the C and $18.3\times10^{-9}J/mm^2$ for the D. Microscopic observation shows that the breaking of the laser treated specimen had been occured through the boundary between HA layer and polymer resin, but the untreated specimen had been occured through the inside of HA coating layer.

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Surface Characteristics of Polymer Coated NiTi Alloy Wire for Orthodontics (폴리머 코팅된 NiTi합금 교정선의 표면특성)

  • Cho, Joo-Young;Kim, Won-Gi;Choi, Hwan-Suk;Lee, Ho-Jong;Choe, Han-Cheol
    • Journal of Surface Science and Engineering
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    • v.43 no.3
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    • pp.132-141
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    • 2010
  • NiTi alloy has been used for orthodontic wire due to good mechanical properties, such as elastic strength and frictional resistance, combined with a high resistance to corrosion. Recently, these wire were coated by polymer and ceramic materials for aesthetics. The purpose of this study was to investigate surface characteristics of polymer coated NiTi alloy wire for orthodontics using various instruments. Wires (round type and rectangular type) were used, respectively, for experiment. Polymer coating was carried out for wire. Specimen was investigated with field emission scanning electron microscopy(FE-SEM), energy dispersive x-ray spectroscopy(EDS) and atomic force microscopy(AFM). The phase transformation of non-coated NiTi wire from martensite to austenite occurred at the range of $14{\sim}15^{\circ}C$, in the case of coated wire, it occurred at the range of $16{\sim}18^{\circ}C$. Polymer coating on NiTi wire surface decreased the surface defects such as scratch which was formed at severe machined surface. From the AFM results, the average surface roughness of non-coated and coated NiTi wire was 13.1 nm, and 224.5 nm, respectively. From convetional surface roughness test, the average surface roughness of non-coated and coated NiTi wire was $0.046{\mu}m$, and $0.718{\mu}m$, respectively.

Effect of Water-Soluble Polymer on the Properties of High Strength Hardened Cement Paste (고강도 시멘트 경화체의 특성에 미치는 수용성 폴리머의 영향)

  • 김정환;최상흘;한기성
    • Journal of the Korean Ceramic Society
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    • v.26 no.5
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    • pp.698-704
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    • 1989
  • Basic investigation for the flexural strength and water stability of hardened cement pastes using ordinary portland cement with water-soluble polyer (hydroxypropyl methyl cellulose ; HPMC) was carried out with 0.2 of water cement ratio. For molding of the specimen, the paste was mixed by twin roll mill. According to increase in the content of HPMC, the setting time of cement paste was delayed and the flexural strength was increased. The maximum flexural strength of hardened cement paste with 5.0wt% of HPMC was about 330 kg/$\textrm{cm}^2$. The expansion of the hardened cement paste immersed in water was increased with the content of water soluble polymer(HPMC). Consequently, the strength and the water stability of the hardened cement pastes were remarkably reduced by the expansion of them.

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Determination of Dynamic Fractrue Toughness for very Brittle Materials (매우 취성인 재료의 동적 파괴인성치 결정법)

  • 이억섭;한유상
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1996.04a
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    • pp.724-728
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    • 1996
  • The instrumented Charpy impact test is generally used to evaluate the dynamic fracture toughness for varying engineering materials. However, the test is known to be difficult to evaluate the dynamic fracture toughness for very brittle materials because of the small crack initiation load. To evaluate the dynamic fracture toughness of verybrittle materials, it is necessary to develop a load sensitive instrumented tup. In this study, a polymer tup, which has small Young's modulus, is used for the instrumented Charpyimpact test and a proper testing method is developed. The results show that the developed method can measure rapidly changing loads from the moment of contact between the tup and the specimen to dynamic crack initation of the very brittle materials.

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Microlens Fabrication by Using Excimer Laser (엑사이머 레이저를 이용한 마이크로렌즈 제작)

  • 김철세;김재도;윤경구
    • Journal of the Korean Society for Precision Engineering
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    • v.20 no.2
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    • pp.33-39
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    • 2003
  • A new microlens fabrication technique, the excimer laser lithography is developed. This bases on the pulsed laser irradiation and the transfer of a chromium-on-quartz reticle on to the polymer surface with a proper projection optics system. An excimer laser lithography system with 1/4 and 1/20 demagnification ratios was constructed first, and the photoablation characteristics of the PMMA and Polyimide were experimentally examined using this system. For two different shapes of microlenses, a spherical lens and a cylindrical lens, fabrication techniques were investigated. One for the spherical lens is a combination of the mask pattern projection and fraction effect. The other for the cylindrical lens is a combination of the mask pattern projection and the relative movement of a specimen. The result shows that various shapes of micro optical components can be easily fabricated by the excimer laser lithography.

The Influence of acid rein upon Tracking resistance of Epoxy Composite Materials (에폭시 복합재료의 내트래킹성에 미치는 산성비의 영향)

  • Son, In-Hwan;Kim, Tag-Yong;Choi, Seong-Min;Kim, Kyung-Hwan;Kim, Jae-Hwan
    • Proceedings of the KIEE Conference
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    • 1997.07e
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    • pp.1813-1815
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    • 1997
  • In this study, in order to develop outdoor insulating materials, SIN(simultaneous interpenetrating polymer network) was introduced to Epoxy resin and the environment resistance was investigated. Six kinds of specimen were manufacture by filler($SiO_2$) content. SEM was untilized in order to confirm their network structure changes. Also, tracking test, UV test and acid rain test were carried out investigate the environment resistance characteristic. Therefore it was confirmed that simultaneous interpenetrating polymer network specimens were more excellent than single network structure specimens. But, acid rain almost never changed resistance.

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Compaction Properties of Fe Powder Fabricated by Warm Compaction (온간성형법으로 제조된 Fe 분말의 성형특성)

  • Kim, Se-Hoon;Lee, Young-Jung;Lee, Jea-Sung;Kim, Young-Do
    • Journal of Powder Materials
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    • v.14 no.3 s.62
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    • pp.185-189
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    • 2007
  • Various approaches have been proposed to increase the green density. Warm compaction method has been used for the reduction of residual stress, the improvement of magnetic properties and the higher densities. In this work, the effect of warm compaction on green density of Fe powder was investigated. After ball-milling of Fe oxide powder for 30 hours, Fe oxide powder was reduced through the hydrogen reduction process. The pure Fe powder and polymer binder were mixed by 3-D tubular mixer. And then the mixed powder was warm-compacted with various compaction pressure and binder contents. The green density of specimen was added polyvinyl binder was higher than any other specimens.

Injection Moulding of Polyetherimide Axi-Symmetric Elements (PEI계 플라스틱 축대칭 부품의 사출 성형에 관한 연구)

  • 하영욱;정태형;이범재
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.11 no.6
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    • pp.68-74
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    • 2002
  • This research covers the development of axi-symmetric plastic elements for injection molding with insert steel such as high stiffness Sabot. The functional requirements of sabot are concentricity and fracture resistance about vertical and horizontal forces. For these, an analysis of characteristics of PEI(polyetherimide) polymer is performed by standard test specimen with accordance of ASTM test guidance. Moldflow analysis and simulation of injection molding process are carried out in order not only to estimate of the warpage but also to predict the characteristics of residual stresses which both product and structure of mold may have. A new vertical side injection machine and transverse mold have been constructed. Results of the measuring concentricity and fracture test after molding of sabot are satisfied to design specification over Cp $ratio{\geq}1.33$. Finally, this technique needs more research application to others axi-symmetric elements having different radius with insert steel md structure analysis from now on.