• Title/Summary/Keyword: Fiber pull Out

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Synergistic bond properties of new steel fibers with rounded-end from carbon nanotubes reinforced ultra-high performance concrete matrix

  • Nguyen Dinh Trung;Dinh Tran Ngoc Huy;Dmitry Olegovich Bokov;Maria Jade Catalan Opulencia;Fahad Alsaikhan;Irfan Ahmad;Guljakhan Karlibaeva
    • Advances in nano research
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    • v.14 no.4
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    • pp.363-373
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    • 2023
  • A novel type of steel fiber with a rounded-end shape is presented to improve the bonding behavior of fibers with Carbon Nanotubes (CNT)-reinforced Ultra-High Performance Concrete (UHPC) matrix. For this purpose, by performing a parametric study and using the nonlinear finite element method, the impact of geometric characteristics of the fiber end on its bonding behavior with UHPC has been studied. The cohesive zone model investigates the interface between the fibers and the cement matrix. The mechanical properties of the cohesive zone model are determined by calibrating the finite element results and the experimental fiber pull-out test. Also, the results are evaluated with the straight steel fibers outcomes. Using the novel presented fibers, the bond strength has significantly improved compared to the straight steel fibers. The new proposed fibers increase bond strength by 1.1 times for the same diameter of fibers. By creating fillet at the contact area between the rounded end and the fiber, bond strength is significantly improved, the maximum fiber capacity is reachable, and the pull-out occurs in the form of fracture and tearing of the fibers, which is the most desirable bonding mode for fibers. This also improves the energy absorbed by the fibers and is 4.4 times more than the corresponding straight fibers.

Assessment of push-pull forces of yarn-carrying carts at some fiber-twisting factories (일부 섬유제품제조업의 밀기-당기기 작업 평가)

  • Lee, Sang-Man;Kim, Sung-Whan;Kim, Seung-Gon;Lee, Chae-Yong
    • Journal of Korean Society of Occupational and Environmental Hygiene
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    • v.21 no.4
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    • pp.209-214
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    • 2011
  • Objectives: To assess the risk of pushing or pulling the yarn-carrying cart, the survey was performed in some fiber manufacturing factories. Methods: We selected 6 fiber-twisting factories which agreed to in-site survey of their workplace. To measure both initial and sustained forces of the push-pull tasks, Chatillon CSD500 dynamometer(2004, Ametek, USA) was used. The mean of 3 tests for the same cart was adopted as the measured forces. Height and width of cart, weight of spooled yarns, and distance of movement were also measured. Inspection of cart wheel, moving path, and the actual hand position while moving was done. Results: More than one pushing or pulling task exceeded the push-pull force limits of design goal in 5 factories. Though the cart was not loaded the heaviest weight in the factory, the measured push or pull force exceeded the limits several times. A few cart wheels were worn out and tangled with pieces of yarn. It was also observed some holes in the moving path. Conclusions: While the push-pull task is not included in the 11 scopes of over-burdened work notified by Korean government, it should be recognized as risk factor of work-related musculoskeletal disorders. The maintenance work such as regular change and frequent cleaning of cart wheel, the use of fitting wheel, and flattening of bumpy floor through the moving path should be advised importantly in the worksite management of work-related musculoskeletal disorders.

Pullout Performance of Reinforcing Fiber Embedded in Nano Materials Cement Mortar with Nano Clay Contents (나노클레이 첨가량에 따른 나노재료 시멘트 모르타르에 정착된 보강섬유의 인발성능)

  • Oh, Ri-On;Park, Chan Gi
    • Journal of The Korean Society of Agricultural Engineers
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    • v.55 no.3
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    • pp.113-121
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    • 2013
  • Recently, it has been studied for the application of nano-materials in the concrete. Applied a small amount of nano-materials can achieve the goal of high strength, high performance and high durability. The small addition of nano clay improves strength, thermal stability, and durability of concrete because of the excellent dispersion. The present study has investigated the effectiveness, when varying with the contents of nano clay, influencing the pull-out behavior of macro synthetic fibers in nano materials cement mortar. Pullout tests conducted in accordance with the Japan Concrete Institute (JCI) SF-8 standard for fiber-reinforced concrete test methods were used to evaluate the pullout performance of the different nano clay. Nano clay was added to the 0, 1, 2, 3, 4 and 5 % of cement weight. The experimental results demonstrated that the addition of nano clay led to improve the pull-out properties as of the load-displacement curve in the precracked and debonded zone. Also, the compressive strength, flexural strength and pullout performance and of Mix No. 1 and No. 2 increased up to the point when nano clay used increased by 2 and 3 % contents, respectively, but decreased when the exceeded 3 and 4 %, respectively. It was proved by verifying increase of the scratching phenomenon in macro synthetic fiber surface through the microstructure analysis on the surface of macro synthetic fiber.

A Study on the Failure Modes of Neat Kevlar Fabric and Kevlar Liquid Armor Impregnated with Shear Thickening Fluid (케블라 직물과 전단농화유체로 함침된 케블라 액체 방탄재의 파단모드 연구)

  • Yoon, Byung-Il;Song, Heung-Sub;Paik, Jong-Gyu
    • Composites Research
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    • v.20 no.3
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    • pp.17-24
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    • 2007
  • In this study, the failure modes by ballistic impacts were studied both for a neat Kevlar woven fabric and a Kevlar liquid armor impregnated with shear thickening fluid (STF) containing silica particles. These two materials showed quite different failure modes macroscopically in ballistic impacts tests used by Cal.22 FSP and 9mm FMJ bullet. Yarn pull-out for the neat Kevlar woven fabric and yarn fracture occurred partially through all plies from 1st ply to last one for the STF-Kevlar are an important energy absorption mechanisms. The results observed by S.E.M showed commonly fiber damage which are torn skin in the longitudinal fiber direction, fiber split axially and fiber fracture for two materials. The reasons why STF-kevlar liquid armor material exhibits excellent ballistic performance are as follow: firstly the increased friction forces between yarn-yarn and fabric-fabric covered with silica particles and secondary the evolution of shear thickening phenomenmon resulting in suppression of yarn mobility.

An Experimental Study on the Effects of Steel Fibers used at R/C Exterior Joints (철근 콘크리트 보-기둥 외측 접합부에 적용된 강섬유의 효과에 관한 실험연구)

  • Choi, Ki-Bong;Oh, Jong-Han;Kim, Jae
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.2 no.3
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    • pp.188-193
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    • 1998
  • An experimental study was performed on the pull-out behavior of 90-deg standard hooks from exterior beam-column connections. The effects of lateral confinement and fiber reinforcement of joint area were investigated. It was concluded ; (1) Substitution of the transverse column (confining) reinforcement with steel fibers at the joint region effectively reduces the extent of cracking in exterior joints caused by pull-out of hooked bars; and (2) The strength and ductility of hooked bars under pull-out forces are positively influenced by substituting the conventional confining reinforcement of exterior joints with steel fibers. Application of steel fibers to exterior joints seems to be an effective technique for improving the anchorage conditions of hooked bars, and also for reducing the congestion of reinforcement in exterior beam-column connections.

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An Experimental Study on the Pull-Out Behaviors of Headed GFRP Rebar in Mortar (정착판 GFRP 근(Rebar)의 모르타르 인발거동에 관한 시험연구)

  • Ji, Hyo-Seon
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.13 no.6
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    • pp.2797-2803
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    • 2012
  • This paper presents the pull-out behaviors of headed glass fiber reinforced polymer (GFRP) rebar embedded in mortar under tension loading. Five specimens with headed GFRP rebars that were anchored in the center of mortar bases were constructed and the pull-out test was conducted. To verify the test results, the finite element analysis was conducted and the results were compared with the FE analysis using ANSYS software package. Based on the test results it was indicated that the CCD(concrete capacity design) failure theory should be adopted and not to use the 45o cone failure theory as the breakout capacity in the headed GFRP rebar embedded in mortar.

A Study on the Improvement of Interfacial Bonding Shear Strength of Ti50-Ni50 Shape Memory Alloy Composite (Ti_{50}-Ni_{50} 형상기억합금 복합체의 계면 접학 전단강도 향상에 관한 연구)

  • Lee, Hyo-Jae;Hwang, Jae-Seok
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.10 s.181
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    • pp.2461-2468
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    • 2000
  • In this paper, single fiber pull-out test is used to measure the interfacial bonding shear strength of $Ti_{50}-Ni_{50}$ shape memory alloy composite with temperature. Fiber and matrix of $Ti_{50}-Ni_{50}$ shape memory alloy composite are respectively $Ti_{50}-Ni_{50}$ shape memory alloy and epoxy resin. To strengthen the interfacial bonding shear stress, various surface treatments are used. They are the hand-sanded surface treatment, the acid etched surface treatment and the silane coupled surface treatment etc.. The interfacial bonding shear strength of surface treated shape memory alloy fiber is greater than that of surface untreated shape memory alloy fiber by from 10% to 16%. It is assured that the hand-sanded surface treatment and the acid etched surface treatment are the best way to strengthen the interfacial bonding shear strength of $Ti_{50}-Ni_{50}$ shape memory composite. The best treatment condition of surface is 10% HNO$_3$ solution in the etching method to strengthen the interfacial bonding shear strength of $Ti_{50}-Ni_{50}$ shape memory alloy composite.

A Study on the Impact Fracture Behavior of Glass Fiber Polypropylene Composites (GF/PP 복합재료의 충격파괴거동에 관한 연구)

  • 엄윤성
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.35 no.4
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    • pp.421-427
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    • 1999
  • The critical fracture energy and failure mechanisms of GF/PP composites are investigated in the temperatures range of the ambient temperature to $-50^{\circ}C$ The critical fracture energy increase as fiber volume fraction ratio increased The critical fracture energy shows a maximum at ambient temperature and it tends to decrease as temperature goes up. Major failure mechanisms can be classfied such as fiber matrix debonding, fiber pull-out and/or delamination and matrix deformation.

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Effect of Pull-out Property by Shape and Mechanical Property of Reinforcing Fiber on the Flexural Behavior of Concrete (보강섬유의 형상과 물성에 따른 인발특성이 콘크리트의 휨거동에 미치는 영향)

  • Kim, Hong-Seop;Nam, Jeong-Soo;Kim, Jung-Hyun;Han, Sang-Hyu;Kim, Gyu-Yong
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.18 no.5
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    • pp.41-50
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    • 2014
  • This study evaluated the bonding property of fiber and flexural behavior of fiber reinforced concrete. Amorphous steel fiber, hooked steel fiber and polyamide fiber was used for evaluation of bonding property and flexural behavior. As a result, the hooked steel fiber was pulled out from matrix when peak stress. However amorphous steel fiber occurred shear failure because bonding strength between fiber and matrix was higher than tensile strength of fiber. Polyamide fibers occurred significantly displacement to peak stress because of elongation of fiber. After that peak stress, fiber was cut off. Amorphous steel fiber reinforced concrete had a greater maximum flexural load compared with hooked steel fiber reinforced concrete because bonding performance between fiber and matrix was high and mixed population of fiber was many. However flexural stress was rapidly reduced in load-deflection curve because of shear failure of fiber. Flexural stress of hooked steel fiber reinforced concrete was slowly reduced because fiber was pulled out from the matrix. In the case of polyamide fiber reinforced concrete, flexural stress was rapidly lowered because of elongation of fiber. However flexural stress was increased again because of bonding property between polyamide fiber and matrix. The pull-out properties of the fiber and matrix has effect on the deformation capacity and flexural strength of fiber reinforced concrete.

Effect of Fluorination on Pull-out Response of Carbon Fiber Embedded in Cement Matrices (플루오르화에 의해 표면개질된 탄소섬유의 시멘트 매트릭스 내 매입인발거동)

  • Jeon Esther;Han Byung-Chan;Yang Il-Seung;Park Wan-Shin;Lee Young-Seak;Yun Hyun-Do
    • Proceedings of the Korea Concrete Institute Conference
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    • 2004.11a
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    • pp.45-48
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    • 2004
  • This paper aimed at the development of hydrophilic carbon fiber with improved tensile strength and ductility, numerous single fiber pullout tests from different cement matrices were performed. Fiber debonding and pullout have a large influence on the tensile stress - crack opening behavior of fiber concrete. Both debonding and pullout depend on the quality of the matrix, as well as on the embedded length of the carbon fiber. In this paper, all fiber pullout tests were carried out using high strength carbon fibers, both without fluorinationed and with fluorinationed carbon fiber.

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