• Title, Summary, Keyword: 연성 단섬유

Search Result 7, Processing Time 0.031 seconds

Reinforcing Characteristics on Volume and Shape of Ductile Short-Fiber in Brittle Matrix Composites (취성기지 복합재료에서 연성 단섬유의 함유량 및 형상에 관한 보강특성)

  • Sin, Ik-Jae;Lee, Dong-Ju
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.24 no.1
    • /
    • pp.250-258
    • /
    • 2000
  • The reinforcing effects of ductile short-fiber reinforced brittle matrix composites are studied by, measuring flexural strength, fracture toughness and impact energy as functions of fiber volume fraction and length. The parameters of fracture mechanics, K and J are applied to assess fracture toughness and bridging stress. It is found that fracture toughness is greatly, influenced by the bridging stress ill which fiber pull-out is occur. For the reinforcing effects as functions of fiber volume fraction($V_f$ = 1, 2, 3 %) and length(L = 3, 6. 10cm), the flexural strength is maximum at $V_f$ = 1% and both fracture toughness.

Unconfined Compressive Strength of Cemented Sand Reinforced with Short Fibers (단섬유를 사용한 시멘트 혼합토의 일축압축강도 특성)

  • Park, Sung-Sik;Kim, Young-Su;Choi, Sun-Gyu;Shin, Shi-Eon
    • Journal of The Korean Society of Civil Engineers
    • /
    • v.28 no.4C
    • /
    • pp.213-220
    • /
    • 2008
  • A study on cemented sand reinforced with short fibers was carried out to improve its unconfined compressive strength and brittle behavior. Nak-dong River sand was mixed with Portland cement and polyvinyl alcohol (PVA) fibers. A PVA fiber widely used for concrete reinforcement is randomly distributed into cemented sand. Nak-dong River sand, cement and fibers with optimum water content were compacted in 5 layers and then cured for 7 days. The effect of fiber reinforcement rather than cementation was emphasized by using a small amount of cement. Weakly cemented sand with a cement/sand ratio less than 8% was fiber-reinforced with different fiber ratios and tested for unconfined compression tests. The effect of fiber ratio and cement ratio on unconfined compressive strength was investigated. Fiber-reinforced cemented sand with 2% cement ratio showed up to six times strength to non-reinforced cemented sand. Because of ductile behavior of fiber-reinforced specimens, an axial strain at peak stress of specimens with 2% cement ratio increases up to 7% as a fiber ratio increases. The effect of 1% fiber addition into 2% cemented sand on friction angle and cohesion was analyzed separately. When the fiber reinforcement is related to friction angle increase, the 8% of applied stress transferred to 1% fibers within specimens.

  • PDF

Structural Behavior of Fiber Reinforced Concrete Mixed with Recycled PET Fiber (재생 PET 섬유가 혼입된 섬유 보강 콘크리트의 구조거동)

  • Kim, Sung Bae;Kim, Hyun Young;Yi, Na Hyun;Kim, Jang-Ho Jay
    • Journal of The Korean Society of Civil Engineers
    • /
    • v.29 no.5A
    • /
    • pp.543-550
    • /
    • 2009
  • This study was performed to prove the possibility of utilizing short plastic fibers made for recycled polyethylene terephthalate (RPET) as a structural material. In order to verify the capacity of RPET fiber, it was compared with polypropylene (PP) fiber, most widely used short synthetic fiber, for fiber volume fraction of 0%, 0.5%, 0.75%, and 1.0%. To measure material properties such as compressive strength, split tensile strength, appropriate tests were performed. Also, to measure the strength and ductility capacities of reinforced concrete (RC) member casted with RPET fiber added concrete, flexural test was performed on RC beams. The results showed that compressive strength decreased, as fiber volume fraction increased. These trends are similarly observed in the tests of PP fiber added concrete specimens. Split cylinder tensile strength of RPET fiber reinforced concrete increased slightly as fiber volume fraction increased. For structural member performance, ultimate strength, relative ductility and energy absorption of RPET added RC beam are significantly larger than OPC specimen. Also, the results showed that ultimate flexural strength and ductility both increased, as fiber volume fraction increased. These trends are similarly observed in the tests of PP fiber added concrete specimens. The study results indicate that RPET fiber can be used as an effective additional reinforcing material in concrete members.

  • PDF

Coupled Analysis with Digimat for Realizing the Mechanical Behavior of Glass Fiber Reinforced Plastics (유리섬유 강화 플라스틱의 역학적 거동 구현을 위한 Digimat와의 연성해석 연구)

  • Kim, Young-Man;Kim, Yong-Hwan
    • Journal of the Computational Structural Engineering Institute of Korea
    • /
    • v.32 no.6
    • /
    • pp.349-357
    • /
    • 2019
  • Finite element method (FEM) is utilized in the development of products to realistically analyze and predict the mechanical behavior of materials in various fields. However, the approach based on the numerical analysis of glass fiber reinforced plastic (GFRP) composites, for which the fiber orientation and strain rate affect the mechanical properties, has proven to be challenging. The purpose of this study is to define and evaluate the mechanical properties of glass fiber reinforced plastic composites using the numerical analysis models of Digimat, a linear, nonlinear multi-scale modeling program for various composite materials such as polymers, rubber, metal, etc. In addition, the aim is to predict the behavior of realistic polymeric composites. In this regard, the tensile properties according to the fiber orientation and strain rate of polybutylene terephthalate (PBT) with short fiber weight fractions of 30wt% among various polymers were investigated using references. Information on the fiber orientation was calculated based on injection analysis using Moldflow software, and was utilized in the finite element model for tensile specimens via a mapping process. LS-Dyna, an explicit commercial finite element code, was used for coupled analysis using Digimat to study the tensile properties of composites according to the fiber orientation and strain rate of glass fibers. In addition, the drawbacks and advantages of LS-DYNA's various anisotropic material models were compared and evaluated for the analysis of glass fiber reinforced plastic composites.

Structural Performance of Reinforced Concrete Shear Columns Strengthened with Sprayed Fiber Reinforced Polymers (Sprayed FRP로 보강된 철근 콘크리트 전단기둥의 보강성능 평가)

  • Lee, Kang Seok;Byeon, In Hee;Lee, Moon Sung
    • Journal of the Korea institute for structural maintenance and inspection
    • /
    • v.11 no.3
    • /
    • pp.132-142
    • /
    • 2007
  • In this study, a structural performance of R/C columns controlled by shear, strengthened with Sprayed FRP, was investigated. For this purpose, six 2/3-scaled column specimens were designed and tested by the pseudo-static reversed cyclic load under a constant axial load, which is 10% of the nominal axial strength of the column. Four specimens were strengthened by Sprayed FRP with different combinations of short fibers (carbon or glass) and resins (epoxy or vinyl ester). For comparison purpose, tests of a specimen strengthened with carbon fiber sheet (CFS) and a control specimen without strengthening were carried out, respectively. The result reveals that shear strengths and ductility capacities of columns strengthened with Sprayed FRP improved remarkably, compared to those of the control column, and the Sprayed FRP technique developed in this study is able to use the strengthening scheme of existing R/C columns.

Flexural Performance Evaluation of HPFRCC Using Hybrid PVA Fibers (하이브리드 PVA 섬유를 이용한 HPFRCC의 휨 성능 평가)

  • Kim, Young-Woo;Min, Kyung-Hwan;Yang, Jun-Mo;Yoon, Young-Soo
    • Proceedings of the Korea Concrete Institute Conference
    • /
    • /
    • pp.753-756
    • /
    • 2008
  • HPFRCC (High-Performance Fiber Reinforced Cementitious Composites), which is relatively more ductile and has the characteristic of high toughness with high fiber volume fractions, can be used in structures subjected to extreme loads and exposed to durability problems. In the case of using PVA(polyvinyl alcohol) fibers, it is noted by former studies that around 2% fiber volume fractions contributes to the most effective performance at HPFRCC. In this study, therefore, compressive and flexural tests were implemented to evaluate the compressive and flexural capacities of HPFRCC while the total fiber volume fractions was fixed at 2% and two different PVA fibers were used with variable fiber volume fractions to control the micro-crack and macro-crack with short and long fibers, respectively. Moreover, specimens reinforced with steel and PVA fiber simultaneously were also tested to estimate their behavior and finally find out the optimized mixture. In the result of these experiments, the specimen consists of 1.6% short fibers (REC 15) and 0.4% long fiber (RF4000) outperformed other specimens. When a little steel fibers added to the mixture with 2% PVA fibers, the flexural capacity was increased, however, when high steel fiber volume fractions applied, the flexural capacity was decreased.

  • PDF

Flexural and Impact Resisting Performance of HPFRCCs Using Hybrid PVA Fibers (하이브리드 PVA 섬유를 이용한 HPFRCCs의 휨 및 충격 성능 평가)

  • Kim, Young-Woo;Min, Kyung-Hwan;Yang, Jun-Mo;Yoon, Young-Soo
    • Journal of the Korea Concrete Institute
    • /
    • v.21 no.6
    • /
    • pp.705-712
    • /
    • 2009
  • HPFRCCs (high-performance fiber reinforced cementitious composites), which is relatively more ductile and has the characteristic of high toughness with high fiber volume fractions, can be used in structures subjected to extreme loads and exposed to durability problems. In the case of PVA (polyvinyl alcohol) fiber, it is noted by former studies that around 2% fiber volume fractions contributes to the most effective performance at HPFRCCs. In this study, flexural tests were carried out to evaluate the flexural behavior of HPFRCCs and to optimize mix proportions. Two sets of hybrid fiber reinforced high performance specimens with total fiber volume fraction of 2 % were tested: the first set prepared by addition of short and long PVA fibers at different combination of fiber volume fractions, and the second set by addition of steel. In addition, in order to assess the performances of the HPFRCCs against to high strain rates, drop weight tests were conducted. Lastly, the sprayed FRP was applied on the bottom surface of specimens to compare their impact responses with non-reinforcing specimens. The experimental results showed that the specimen prepared with 1.6% short fibers (REC 15) and 0.4% long fiber (RF4000) outperformed the other specimens under flexure, and impact loading.