• 한국공작기계학회논문집
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• 제17권3호
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• pp.101-107
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• 2008

A composite mechanics for discontinuous fiber reinforced polymer matrix composites(PMC) is analysed in order to predict fiber axial stresses. In continuum approach. frictional slip which usually takes place between fibers and polymers is accounted to derive PMC equations. The interfacial friction stress is treated by the product of the coefficient of friction and the compressive stress norma1 to the fiber/matrix interface. The residual stress and the Poisson's contraction implemented by the rule of mixture(ROM) are considered for the compressive stress normal to the fiber/matrix interface. In addition. the effects of fiber aspect ratio and fiber volume fraction on fiber axial stresses are evaluated using the derived equations. Results are illustrated numerically using the present equations with reasonable materials data. It is found that the fiber axial stress in the center region shows no great discrepancy for different fiber aspect ratios and fiber volume fractions while some discrepancies are shown in the fiber end region.

• 한국구조물진단유지관리공학회 논문집
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• 제16권1호
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• pp.110-119
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• 2012

최근 고부식 환경에 놓여 있는 철근 콘크리트 구조물의 철근 부식 문제를 해결할 수 있는 방안 중 하나로 뛰어난 내부식성을 가진 섬유복합체(Fiber Reinforced Polymer, FRP)로 제작된 보강근이 주목받고 있다. 유리섬유복합체로 제작된 보강근이 상용화된 상태이나 가격, 철근보다 낮은 탄성계수, 취성파괴 특성 등의 이유로 사용 실적은 많지 않은 것이 현실이다. 이러한 문제점을 해결하기 위한 방편 중 하나는 유리섬유복합체 보강근의 성능을 고도화하는 것이다. 성능 고도화를 통해 강도 대비 가격을 낮출 수 있으며, 인장성능을 향상시킬 수 있다. 본 연구는 주어진 재료와 조건 하에서 보강근 성능에 영향을 미치는 인자들의 효율성 향상을 통한 고인장 성능 유리섬유복합체 보강근의 개발에 관한 것이다. 이를 위해 구성재료와 제작방법 등 유리섬유복합체 보강근의 인장성능에 영향을 미치는 인자들에 대해 분석을 수행하여 개선 방안을 제안하였으며, 이를 통해 보강근의 주재료인 유리섬유의 성능을 기존 제품보다 더욱 효율적으로 활용하는 보강근을 제작하였으며, 다양한 변수에 대한 인장시험을 통하여 그 성능을 비교 분석함으로써 개선 방안의 적절성을 검증하였다.

• Advances in nano research
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• 제12권2호
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• pp.151-165
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• 2022

Micro-scale serpentine structure fibers are widely used as flexible sensor in the manufacturing of micro-nano flexible electronic devices because of their outstanding non-linear mechanical properties and organizational flexibility. The use of melt electrowriting (MEW) technology, combined with the axial bending effect of the Taylor cone jet in the process, can achieve the micro-scale serpentine structure fibers. Due to the interference of the process parameters, it is still challenging to achieve the precise deposition of micro-scale and high-consistency serpentine structure fibers. In this paper, the micro-scale serpentine structure fiber is produced by MEW combined with axial bending effect. Based on the controlled deposition of MEW, applied voltage, collector speed, nozzle height and nozzle diameter are adjusted to achieve the precise deposition of micro-scale serpentine structure fibers with different morphologies in a single motion dimension. Finally, the influence mechanism of the above four parameters on the precise deposition of micro-scale serpentine fibers is explored.

• 한국생산제조학회지
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• 제21권2호
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• pp.252-258
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• 2012

A study of terahertz waves was made for the nondestructive evaluation of FRP (Fiber reinforced plastics) composite materials. The terahertz systems were consisted of time domain spectroscopy (TDS) and continuous wave (CW). The composite materials investigated include both non-conducting polymeric composites and conducting carbon fiber composites. Terahertz signals in the TDS mode resembles that of ultrasound; however, unlike ultrasound, a terahertz pulse was not able to detect a material with conductivity. The CFRP (Carbon fiber reinforced plastics) laminates were utilized for confirming the experimentation in the terahertz NDE. In carbon composites the penetration of terahertz waves is quite limited and the detection of flaws is strongly affected by the angle between the electric field direction of the terahertz waves and the intervening fiber directions. A refractive index (n) was defined as one of mechanical properties; so a method was obtained in order solve the "n" in the material with non-conductivity. The usefulness and limitations of terahertz radiation are investigated for the NDE of FRP composites.

• 한국생산제조학회지
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• 제21권4호
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• pp.619-624
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• 2012

In this study, MMT/fiber/polymer composites were fabricated by impregnating chopped strand glass mat into a vinylester resin mixed with clay. Tensile tests has been performed by using a universal testing machine to determine the effect of MMT addition on the tensile properties of MMT/chopped strand glass fiber/vinylester composites. And some pictures which are magnified cross section of breaking parts are has been taken by using a FE-SEM to confirm the behavior at breaking. The contents ratio of MMT applied in the composites were 0.5, 1.0, 1.5, and 2.0 wt% respectively. It has been found that the tensile strength and elastic modulus of MMT/chopped strand glass fiber/vinylester composites were improved at a proper content of MMT. Tensile strength and elastic modulus were maximized at a content of 1.0 wt% due to most effective dispersion of MMT. On the contrary, the failure strain was increased as MMT content was increased.

• Composites Research
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• 제27권1호
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• pp.19-24
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• 2014

본 연구에서 아마/비닐에스테르(Flax/vinyl ester)를 적용한 친환경 구조물 설계를 위한 선행 연구로서 아마/비닐 에스테르 자연 섬유 복합재료의 기계적 물성치를 분석하였다. 시편 제작을 위해 VARTM 제작 공법이 적용되었다. 참고문헌에서 제시한 자연 섬유 복합재료의 물성치와 본 연구에서 제작된 시편의 물성치를 비교하였다. 이 결과를 바탕으로 아마/비닐 에스테르 복합재료가 친환경 구조물에 적용하는 것이 유리함을 확인하였다.

• 펄프종이기술
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• 제40권4호
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• pp.1-9
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• 2008

The utilization of non-woody fibers with the fast growing annual plants has occurred in the paper industry to replace wood and preserve environment of the earth. The non-woody fibers generally used for papermaking are paper mulberry, gampi, manila hemp, rice straw, bamboo, and coton linter etc.. Recently Kenaf has been spot-lighted for the same application. Kenaf is an annual plant of Hibiscus species of Malvaceae family. Kenaf, a rapid growing and high harvesting non-woody fiber plant, was identified as one of the promising fiber sources for the production of paper pulp. This study was carried out to investigate the pulping characteristics of Kenaf bast fiber for Hanji (traditional Korean paper) manufacturing by different pulping methods, such as alkali, alkali-peroxide and sulfomethylated pulpings. It was possible to make superior grade of Hanji. Especially sulfomethylated pulping was resulted in superior pulp in terms of higher yields and qualities in comparison to those of the other pulping methods. Hanji from sulfomethylated pulp was shown the highest brightness of over 60% and higher sheet strength. In addition, the morphological features of pulp fibers (pulp compositions) affect to the sheet properties. Therefore the effect of fiber distribution index(FDI) which was calculated from the data of Confocal laser scanning microscopy(CLSM) on the sheet properties of Kenaf Hanji was also discussed.

• 한국기계가공학회지
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• 제21권9호
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• pp.12-20
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• 2022

Delamination and burr defects are important problems in drilling fiber reinforced plastics. A method for measuring FRP drilling defects has been studied. Delamination and burr factors were defined as the relative length or area. Using these factors, the effects of tool shape and drilling conditions on delamination and burr were studied. In this study, the defects that occur when drilling a glass-carbon fiber hybrid composite were compared in terms of three factors. In the glass-carbon fiber hybrid composite, the effects of the feed rate and tool point angle on the delamination and burr factors were similar to those in previous studies. The diameter of the tool did not affect the defect factor. A circular burr was generated in a drill tool with a point angle of 184°, and a relatively small deburring factor was observed compared with a tool with a point angle of 140°.

• 한국섬유공학회:학술대회논문집
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• 한국섬유공학회 2003년도 봄 학술발표회 논문집
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• pp.119-121
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• 2003

Hydroentanglement describes a versatile process for manufacturing nonwoven fabrics using foe, closely speed, high-velocity jets of water and entangles loose arrays of fibers. The resultant fabrics rely primarily on fiber-to-fiber friction to achieve physical integrity and are characterized by relatively high strength, flexibility, and conformability. These technologies can use efficiently the majority of all types of fibers and produce fabrics that could achieve properties equivalent to reverts. (omitted)

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2003년도 추계학술대회
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• pp.131-136
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• 2003

Five expensive sensors are necessary to control a magnetic bearing system. The sensor price rate of magnetic bearing system is high. So it is necessary that cheap and good sensor is developed. The optical fiber displacement sensor is adaptive to satisfy this condition. We can design magnetically suspended spindle based on static characteristic of optical fiber displacement sensor developed. The controller can be designed by decoupled feedback PD. Therefore, it is simpler than any other controller comparatively.