• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.1
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• pp.14-20
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• 2017

Ultra high performance concrete is inevitably used in case of skyscraper and super long span bridge. In general, the flexural and the tensile strengths of concrete are lower than the compressive strength, so brittle cracks occur and energy absorption ability is lowered. In order to solve this problem, this study is intended to examine the effect of the steel fiber volume fraction and aspect ratio on the mechanical properties of ultra high performance concrete. In series I, 20-mm straight steel fiber was added with a volume fraction of 0, 1.0, 1.3, 1.5 and 2.0%. In series II, 16-mm steel fiber was added with a volume fraction of 0, 1, and 1.5%, and then mechanical properties were examined according to aspect ratio. In the results of experiment, a difference in compressive strength was insignificant. However, regarding the flexural strength and tensile strength, as the volume fraction and aspect ratio increased, flexural performance and tensile performance improved.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.23-28
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• 2001

Since the steel fiber used in concrete to improve shear and ductility capacity, a number of laboratory tests have been studied to define shear strengthening effect according steel fiber contents in concrete. This study investigates shear strengthening effect of steel fiber in RC columns according to compression strength of concrete. From the structural performance test, following conclusions can be made; the maximum enhancement of shear strengthening effect can be achieved at about 1.0 %~l.5 % of steel fiber contents in comparison with shear capacity ratio, and ductility capacity slightly improved as steel fiber contents increased.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.10a
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• pp.321-327
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• 1996

The result of an experimental study on the mechanical properties of different types of polypropylene fiber reinforced concrete are presented in this paper. This study has been performed to obtain the properties of PFRC such as slump, Vee-Bee time, compressive strength, tensile strength, flexural strength, toughness and resistance to impact. The test variables are fiber content, fiber types, fiber length and W/C ratio. Polypropylene fibers were effective in reinforcing the matrix. A remarkable increase in toughness was observed by the addition of polypropylene fibers.

• Asian-Australasian Journal of Animal Sciences
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• v.18 no.8
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• pp.1116-1124
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• 2005

The influence of fiber content of hay (low-fiber 47% NDF and high-fiber 62% NDF of DM) and concentrate level (high 50% and low 20% of ration DM) on chewing activity, passage rate and nutrient digestibility were tested on four restrict-fed (11.1 to 13.7 kg DM/d) Holstein cows in late lactation. Aspects of ruminal fermentation and digesta particle size distribution were also investigated on two ruminally cannulated (100 mm i.d.) cows of the same group of animals. All digestion parameters studied were more affected by the fiber content of the hay and its ratio to non structural carbohydrates than by the concentrate level. Giving a diet of high-fiber (62% NDF) hay and low concentrate level (20%) increased chewing activity but decreased solid passage rate and total digestibility of nutrients due to a limited availability of fermentable OM in the late cut fiber rich hay. A supplementation of high-fiber hay with 50% concentrate in the diet seems to improve the ruminal digestion of cell contents, whilst a depression of the ruminal fiber digestibility was not completely avoided. Giving a diet of low-fiber (47% NDF) hay and high concentrate level (50%) reduced markedly the chewing and rumination activity, affected negatively the rumen conditions and, consequently, the ruminal digestion of fiber. A reduction of the concentrate level from 50 to 20% in the diet of low-fiber hay improved the rumen conditions as reflected by an increase of the ruminal solid passage rate and of fiber digestibility and in a decrease of the concentration of large particles and of the mean particle size of the rumen digesta and of the faeces. Generally, it can be summarised that, (i) concentrate supplementation is not a strategy to overcome limitations of low quality (fiber-rich) hay, and (ii) increase of the roughage quality is an effective strategy in ruminant nutrition, especially when concentrate availability for ruminants is limited.

• Composites Research
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• v.19 no.6
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• pp.16-22
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• 2006

The puncture properties under various conditions were investigated for the optimum conditions to yield the best properties. Fiber aspect ratio(AR: length of fiber/diameter of fiber), interphase condition and fiber content were considered as variables which impact the puncture force and friction force. The puncture force of short-fiber reinforced rubber increases up to 3.4 times compared to the virgin material. The better interphase condition shows the higher puncture force at given fiber AR and fiber content. The friction force of the matrix and reinforced rubber with a fiber AR below 155 does not exist. The friction force of the reinforced rubber with the good interphase condition and high fiber AR is higher than puncture force of matrix. Overall, it was found that the interphase condition, fiber AR and fiber content have an important effect on the puncture properties.

• Composites Research
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• v.20 no.6
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• pp.28-33
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• 2007

The puncture properties of short-fiber reinforced rubber were investigated as functions of fiber aspect ratio(AR: length of fiber/diameter of fiber), fiber content, specimen size and testing velocity. The puncture stresses of the matrix and short-fiber reinforced rubber decreased with specimen size, and increased with testing velocity at same specimen size. As the fiber AR increased the puncture stress at given fiber content also increased. The problem of the specimen shape was investigated by the comparison of the tensile strength with puncture stress. The forces acting in the membrane wall of the matrix and the short-fiber reinforced rubber showed a similar data regardless of specimen size. And those increased with testing velocity at same specimen size. As the fiber AR increased the force acting in the wall at given fiber content also increased. Overall, it was found that the specimen size, testing velocity had an important effects on the puncture properties.

• Proceedings of the Korean Fiber Society Conference
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• 1988.06a
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• pp.34-34
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• 1988

The pyroelectricity of poly(vinylidenefluoride) films prepared by varying the draw ratio and the poling field was investigated. As the draw ratio and the electric field on poling of the drawn samples increased, so did the pyroelectric coefficient. But the effect of electric field on the pyroelectricity was greater than that of draw ratio. The pyroelectric and piezoelectric activities could be explained by the polarization using the thermally stimulated current. The relation between pyroelectric coefficient and piezoelectric stress constant showed a good linearity.

• Proceedings of the Korean Fiber Society Conference
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• 1994.10a
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• pp.135-136
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• 1994

Anionic water dispersible copolyesters were synthesized by the polycon-densation of dimethyl isophathalate/5-sodium sulfo dimethyl isophathalate with ethylene glycol/diethylene glycol. Structrual analyses such as NMR, Irm WAXD analyses were done and copolyesters were found to be correctly synthesized. Relation between feed ratio and composition ratio of EG/DEG in copolyesters was confirmed by NMR analysis. Solubility test was done to find out optimum conditon of DMS feed ration of 10 mol% in dimethyl esters. Water resistance of copolyesters decreased with the increase of DMS or DEG molar feed ratio.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.11a
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• pp.15-16
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• 2017

In this study, the flexural behavior of fiber-reinforced concrete by fiber type were evaluated. As a result, the flexural strength of the hooked steel fiber-reinforced concrete(HSFRC) was lower than that of the amorphous metallic fiber reinforced concrete(AFRC), however it was shown strain-softening behavior by the pull-out of fiber. The flexural strength and the equivalent flexural strength of polyamide fiber-reinforced concrete(PAFRC) were lower than other specimens, but the equivalent flexural strength ratio was similar to that of AFRC. The flexural behavior of the fiber-reinforced concrete was associated with the bonding and pull-out properties of the fiber and matrix depending on the fiber type.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.10
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• pp.1823-1825
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• 2007

Based on Faraday effect, the variation of current flowing through the conductor can be encoded as that of azimuth angle of light polarization propagating through the fiber coil wound onto the conductor. The amount of current can be obtained by measuring the variation of the light intensity transformed from that of the azimuth angle through a polarization analyzer. In this paper we propose a fiber-optic current sensor system that employs a fiber polarization analyzer as a sensor interrogation device. The fiber polarization analyzer was prepared by inscribing a long-period fiber grating on a high birefringent fiber. At the fixed wavelength of 1522.5 nm, the fabricated fiber device has the polarization extinction ratio of more than 25 dB. The measurement of large current up to 600 Arms was accomplished based on a simple fiber interrogation device and the measurement output of the sensor system showed a good linearity.