• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.2
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• pp.158-165
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• 2019

The purpose of this study is to investigate analytically the flexural behavior of beam reinforced by an alkali-activated slag-based fiber-reinforced composite. The materials and mixture proportion were selected to manufacture an alkali-activated slag-based fiber-reinforced composite with high tensile strain capacity over 7% and compressive strength and tension tests were performed. The composite showed a compressive strength of 32.7MPa, a tensile strength of 8.43MPa, and a tensile strain capacity of 7.52%. In order to analyze the flexural behavior of beams reinforced by ultra-high-ductile composite, nonlinear sectional analysis was peformed for four types of beams. Analysis showed that the flexural strength of beam reinforced partially by ultra-high-ductile composite increased by 8.0%, and the flexural strength of beam reinforced fully by ultra-high-ductile composite increased by 24.7%. It was found that the main reason of low improvement in flexural strength is the low tensile strain at the bottom of beam. The tensile strain at bottom corresponding to the flexural strength was 1.38% which was 18.4% of tensile strain capacity of the composite.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.3
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• pp.118-125
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• 2013

The synthetic fibers including Polyvinyl alcohol and Polyethylene fibers have been successfully used in the manufacture of high ductile fiber reinforced cementitious composites. Polypropylene (PP) fiber has also been used in composites, not for the purpose of achieving a high level of tensile ductility but to improve the fire resistance performance of concrete exposed to high temperatures. This paper discusses the method for enhancing the performance of composites supplemented with PP fiber. Five types of mixture proportions were designed with high volume fly ash for testing the performance of composites. Type I cement and fly ash F were used as binding materials. The water-to-binder ratio was 0.23~0.25, and the amount of PP fiber used was 2 vol%. Polystyrene bead were also used to increase the tensile ductility of composites. A series of experiments including slump, density, compression and uniaxial tension tests were performed to evaluate the performance of cementitious composites supplemented with PP fiber. From the test results, it was exhibited that the performance of composites supplemented with PP fiber can be enhanced by adopting the mechanics and statistics theory.

• Journal of the KSME
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• v.31 no.3
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• pp.293-299
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• 1991

단섬유보강 금속복합재료의 2차가공은 금속복합재료의 넓은 범위 응용을 위해 필히 요구된다. 여러 가공방법 중 하나인 열간압출시 보강섬유파괴 및 계면에서의 접합분리 및 균열발생이 없는 제조공정의 최적화를 위해서 가공시 내부조직의 소성변형 기구 규명보다 압출력에 의한 응력분 포와 기지재료와 보강섬유 사이 계면 변화 및 기계적 특성 관계규명이 정량적으로 요구된다. 본 글에서는 유한요소법을 이용하여 계면에서의 접합상태를 임의로 가정하여 압출조건에 따른 압 출후의 보강섬유 방향 및 계면균열 및 접합분리를 거시적으로 예측하고, advanced shear-lag을 이용하여 균열 전, 후의 응력. 변형관계를 미시적으로 규명할 수 있음을 제시하였다. 그러나 향후 현상적 모델인 shear-lag 모델을 수학적 모델인 균질화법에 도입하면 미시적. 거시적 거 동해석이 함께 요구되는 금속복합재료의 열간압출거동 해석을 일체적으로 행할 수 있어 효율적 이고 정확한 예측이 가능하리라고 사료된다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.4
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• pp.9-18
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• 2016

The thermal and mechanical properties of fiber-reinforced cement-based composite for solar thermal energy storage were investigated in this paper. The effect of the addition of different cement-based materials to Ordinary Portland cement on the thermal and mechanical characteristics of fiber-reinforced composite was investigated. Experiments were performed to measure mechanical properties including compressive strength before and after thermal cycling and split tensile strength, and to measure thermal properties including thermal conductivity and specific heat. Test results showed that the residual compressive strength of mixtures with OPC and slag was greatest among cement-based composite. Thermal conductivity of mixtures including graphite was greater than that of any other mixtures, indicating favor of graphite for improving thermal transfer in terms of charging and discharging in thermal energy storage system. The addition of CSA or zirconium increased specific heat of fiber-reinforced cement-based composite. Test results of this study could be actually used for the design of thermal energy storage system in concentrating solar power plants.

• Journal of the Korea Concrete Institute
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• v.22 no.4
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• pp.575-583
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• 2010

This research investigated the influence of the number of twist on single fiber pullout behavior of Twisted steel (T-) fiber and tensile behavior of high performance cementitious composites reinforced with the (T-) fibers (HPFRCC). Micromechanical pullout model for T- fibers has been applied to analytically investigate the influence of various fiber parameters including the number of twist on single fiber pullout behavior; and, to optimize the number of twist to generate larger pullout energy during fiber pullout without fiber breakage. In addition, an experimental program including single fiber pullout and tensile tests has been performed to investigate the influence of twist ratio experimentally. Two types of T- fiber with different twisted ratios, T(L)- fiber (6ribs/30 mm) and T(H)- fiber (18ribs/30 mm), were tested. T(L)- fiber produced higher equivalent bond strength (larger pullout energy) although T(H)- fiber produced higher pullout stress during pullout since T(H)- fiber showed fiber breakage during pullout. Tensile test results confirmed that T(L)- fiber in high strength mortar generates better tensile performance of HPFRCC, e.g., load carrying capacity, strain capacity and multiple micro-cracking behavior.

• Korean Journal of Materials Research
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• v.4 no.7
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• pp.733-740
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• 1994

Oxidized-PAN fiber reinforced composite(OFRP), carbon fiber reinforced composite(CFRP), aramid fiber reinforced composite(AFRP), and glass fiber reinforced composite(GFRP) were fabricated with phenolic resin matrix by hot press molding. We tested the friction coefficient and wear rate varying with fiber weight fraction and observed the effect of fibers according to characteristics of individual reinforcement. When the amount of aramid fiber was 45wt%, average friction coefficient was maximum value of 0.353~0.383, where as, when the amount of pitch based carbon fiber was 45wt%, average friction coefficient was the lowest value of 0.164~0.190. The wear rate of AFRP and CFRP was low, but that of GFRP and OFRP increases drastically in the case of increasing of fiber weight fraction. Wear diagram of OFRP was unstable, but that of CFRP and AFRP was a bit stable. Through very unstable diagram of GFRP, we found that friction stability of GFRP was the lowest.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.04a
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• pp.1-4
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• 2003

사회기반기설을 구축하는 다양한 토목·건축 분야의 주요 콘크리트 구조부재에 탄소섬유시트를 비롯한 섬유복합재료를 이용하여 보수·보강하는 공법은 최근에 세계적으로 많이 활용되고 있는 신공법 중에 하나이다. 기존의 보수·보강재료에 비해 섬유 복합재료에 의한 시공방법의 장점은 구조부재의 내하력을 증가시킬 수 있고 기존에 발생한 균열을 구속하는 효과를 얻을 수 있다. (중략)

• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.6
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• pp.675-689
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• 2019

Development of smart construction materials with both self-strain and self-damage sensing capacities is still difficult because of little information about the self-damage sensing source. Herein, we investigate the effects of the matrix strength, fiber geometry, and fiber content on the electrical resistivity of steel-fiber-reinforced cement composites by multi-fiber pullout testing combined with electrical resistivity measurements. The results reveal that the electrical resistivity of steel-fiber-reinforced cement composites clearly decreased during fiber-matrix debonding. A higher fiber-matrix interfacial bonding generally leads to a higher reduction in the electrical resistivity of the composite during fiber debonding due to the change in high electrical resistivity phase at the fiber-matrix interface. Higher matrix strengths, brass-coated steel fibers, and deformed steel fibers generally produced higher interfacial bond strengths and, consequently, a greater reduction in electrical resistivity during fiber debonding.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.9
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• pp.135-142
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• 1999

A constitutive model was proposed to study the effects of fiber waviness on the elastic properties of unidirectional composite materials. The predictions showed that the degree of fiber waviness significantly affected the elastic properties of composite materials. A special fabrication technique was developed for thic composite materials with various fiber waviness ratios. Tensile, compressive and flexural tests were conducted to obtain the elastic properties of composite materials with fiber waviness experimentally. The experimental result were in good agreement with the predictions.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.1
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• pp.130-140
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• 2007

Fiber-sheet and steel-plate strengthening methods have been mainly used for strengthening the RC structures. However, recently the application of these two methods have dramatically decreased due to premature debonding failure between concrete surface and fiber-sheet and heavy self-weight of steel-plate. This article presents experimental results of shear behavior in RC beams strengthened with GSP(Glass fiber-Steel composite Plate). The thin steel plate in GSP makes usage of the anchoring system possible, which could delay or prevent the premature debonding failure. Three reference beams and 60 strengthened beams with GSP were tested. The experimental results showed that strengthened beams with GSP considerably increased in shear capacity compared with the reference beams.