• 한국기계가공학회지
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• 제21권4호
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• pp.39-45
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• 2022

In this study, it was verified that carbon-ceramic brake discs can replace existing cast-iron brake discs of the same size. In addition, a method of pretreating carbon fiber to secure heat dissipation characteristics while using a small amount of carbon fiber was established. The thermal conductivity and bending strength characteristics were analyzed according to the carbon content, and brake braking tests were conducted. Through pretreatment, the maximum temperature was lowered by 16 ℃ compared to the case using only carbon fiber, and the cooling rate was improved by approximately 10% compared to metal brake discs. However, the total heat capacity increased as the mass increased owing to the reaction. Thus, the measured temperature was higher than that of the metal brake disc; therefore, additional research is required.

• 대한건축학회논문집:구조계
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• 제34권1호
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• pp.11-18
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• 2018

An experimental study on the ultimate behaviors of the mild carbon steel (SPHC) fillet-welded connection is presented in this paper. Seven specimens were fabricated by the shielded metal arc welding (SMAW). All specimens failed by typical block shear fracture in the base metal of welded connections not weld metal. Block shear fracture observed in the base metal of welded connection is a combination of single tensile fracture transverse to the loading direction and two shear fractures longitudinal to the loading direction. Test strengths were compared with strength predictions by the current design equations and suggested equations by previous researchers. It is known that current design specifications (AISC2010 and KBC2016) and Oosterhof & Driver's equation underestimated overly the ultimate strength of the welded connection by on average 44%, 31%, respectively and prediction by Topkaya's equation was the closest to the test results. Consequently, modified equation is required to be proposed considering the stress triaxiality effect and material property difference on the block shear strength for base metal fracture in welded connections fabricated with mild carbon steel.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 추계학술대회 초록집
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• pp.76.1-76.1
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• 2010

Recently, many efforts to solve the durability problem of PEM fuel cell are carried on constantly. However, despite this attention, durability researches of gas diffusion layer (GDL) are not much reported yet. Generally, GDL of PEM fuel cell experiences three external attacks, which are dissolution of water, erosion of gas flow, corrosion of electric potential. In this study, among these degradation factors, carbon corrosion of electric potential was focused and investigated with accelerated carbon corrosion test. Through the test, it is confirmed that carbon corrosion occurred at GDL, and corroded GDL decreased a performance of operating fuel cell. The property changes of GDL were measured with various methods such as air permeability meter, pore distribution analyzer, thermo gravimetric analyzer, and tensile stress test to discover the effects of carbon corrosion. Carbon corrosion caused not only loss of weight and thickness, but also degradation of mechanical strength of GDL. In addition, to analysis the reason of GDL property changes, a surface and a cross section of GDL were observed with scanning electron microscope. After 100 hours test, the GDL showed serious damage in center of layer.

• 한국콘텐츠학회논문지
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• 제20권12호
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• pp.529-536
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• 2020

본 논문에서는 동결융해 작용을 받는 철근콘크리트 압축부재의 내구성 증진 효과를 알아보기 위하여 DFRCC(고인성 섬유 시멘트 복합재료)와 탄소섬유시트를 사용하여 보수·보강을 실시한 철근콘크리트 기둥을 대상으로 동결융해시험을 실시하여 압축강도 및 동탄성계수를 측정하고 비교 평가한 실험적 연구결과를 제시하였다. 이를 위해 100x100x400mm 크기의 기둥형 부재를 총 24개 제작하여 KS F 2456 및 KS F 2453에 따른 동결융해시험과 압축강도 시험을 각각 실시하였다. 부재단면에 4D10의 압축철근을 배치하였으며, 보수보강은 부재의 4면에 각각 실시하였다. 동결융해시험에서는 100, 200, 300Cycle의 각 세단계마다 동탄성계수를 산정하였다. 실험결과, 압축강도에서는 섬유시트를 사용한 경우가 DFRCC의 경우보다 약 5% 정도 큰 양상을 보였으며, 동탄성계수에서는 비슷한 결과를 나타내었다. 이는 공시체 크기에 비해 상대적으로 철근양이 많이 배근되어 간섭을 일으킨 것으로 추정되며, 실제 노후화된 기둥부재의 보수보강을 통한 실질적이고 추가적인 연구와 실험이 필요한 것으로 판단된다.

• Composites Research
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• 제31권6호
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• pp.379-384
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• 2018

본 연구에서는 동일한 표면 형태를 가지는 탄소섬유에 다양한 사이징제를 처리함에 따라 발생하는 에폭 시 수지의 유동 특성 변화를 분석하였다. 동적 접촉각(DCA) 측정을 통해 단일 탄소섬유의 젖음성(Wettability)을 측정하였다. DCA 측정 결과와 함침 특성 간의 연관성을 살피기 위해 Wicking test와 VARTM test를 수행하였다. 추가적으로, 탄소섬유의 표면 에너지 등 다양한 표면 특성을 분석하였으며 Micro-droplet test를 통해 수지와 탄소섬유계면의 계면전단강도를 측정하였다. 이러한 실험 결과를 기반으로, 함침 속도의 증대를 위해서는 탄소섬유의 사이징제가 적정 수준의 표면 에너지를 가져야 하며, 사이징제의 화학적 조성을 조정하여 에폭시 수지의 유동 특성과 계면전단강도가 모두 개선 가능함을 확인하였다.

• 한국구조물진단유지관리공학회 논문집
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• 제10권4호
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• pp.183-193
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• 2006

본 연구는 탄소섬유시트로 보강된 철근콘크리트 보에 정적하중과 반복하중이 작용할 때의 거동을 다루고 있다. 탄소섬유시트로 보강된 RC보의 정적실험 결과를 기준으로 반복하중 실험을 수행하였다. 반복하중 실험의 변수는 탄소섬유시트 겹수, 단부 U밴드 유무, 반복하중 재하속도 등이 있다. 실험결과를 통해 단조증가하중과 반복하중 하에서의 에너지 소산량과 휨 강성의 변화, 연성특성, 강도특성, 휨 거동 등을 고찰하며, 또한 탄소섬유시트의 파단변형률을 평가하였다. 본 연구에서는 반복하중 실험 결과를 바탕으로 탄소섬유시트로 보강된 RC보의 정적 및 동적 휨 보강 해석 및 설계에 필요한 기초자료를 제시하고자 한다.

• Carbon letters
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• 제28권
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• pp.9-15
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• 2018

In the aerospace field, Carbon/Cork composites have been used for rocket propulsion systems as a light weight structural component with a high bending stiffness and high thermal insulation properties. For the fabrication of a carbon composite with a heat insulation cork part, the bonding properties between them are very important to determine the service life of the Carbon/Cork composite structure. In this study, the changes in the interfacial adhesion and mechanical properties of Carbon/Cork composites under accelerated aging conditions were investigated. The accelerated aging experiments were performed with different temperatures and humidity conditions. The properties of the aged Carbon/Cork composites were evaluated mainly with the interfacial strength. Finally, the lifetime prediction of the Carbon/Cork composites was performed with the long-term property data under accelerated conditions.

• 대한금속재료학회지
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• 제50권2호
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• pp.93-99
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• 2012

The mechanical properties of nano composites were evaluated for structural performance in order to enhance their applicability to the car and machine industrial fields. Carbon fiber reinforced plastics (CFRP) and GFRP were manufactured by vacuum-assisted resin transfer molding (VARTM) process with good mechanical properties. Tensile test was conducted to obtain the process factor of each composite. Also, carbon nano fiber (CNF) was dispersed in the composites and the relationship between the mechanical property and the CNF fraction was compared. The tensile strength and stiffness of 0/90 laminated CFRP were the best. CFRP/CNF (0.5 wt.%) was confirmed to be an excellent material for its elasticity and tensile strength.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 1999년도 추계학술발표대회 논문집
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• pp.32-35
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• 1999

Poly(arylene ether phosphin oxide) (PEPO), Udel$^{\circledR}$ P-1700, Ultem$^{\circledR}$ 1000. poly(hydroxy ether) (PHE), carboxy modified poly(hydroxy ether)(C-PHE) and poly(hydroxy ether ethanol amine) (PHEA) were utilized for a coating of carbon fibers. Interfacial shear strength(IFSS) of polymers to carbon fibers was also evaluated in order to understand the adhesion mechanism. IFSS was measured via micro-droplet tests, and failure surfaces were analyzed by SEM. Diffusion between polymer and vinyl ester resin was investigated as a function of styrene content; 33. 40 or 50wt.% and the solubility parameters of polymers were calculated. The results were correlated to the interfacial shear strength. The highly enhanced interfacial shear strength (IFSS) was obtained with PEPO coating, and marginally improved IFSS with PHE, Udel$^{\circledR}$ and C-PHE coatings, but no improvement with PHEA and Ultem$^{\circledR}$ coatings.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회 논문집(II)
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• pp.1019-1024
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• 2000

Carbon fiber sheet has been widely used for the strengthening of the concrete buildings structures due to its excellent physical properties such as high strength, lightness and high durability. Bond strength or behavior, on the other, hands, between carbon fiber sheet and concrete is very important in strengthening the concrete member using CFS. Also the bond failure mechanism between CFS and concrete should be fully verified and understood. This study is to investigate the bond strength of CFS to th concrete by the direct pull-out test and the tensile-shear test methods. From the tests, the average bond stress, $$\tau$_{y}$ and the effective bond length, $$\ell$_{ｕ}$ are acquired.