• 한국재료학회지
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• 제3권3호
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• pp.292-299
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• 1993

본 연구에서는 탄소/탄소복합재료의 마모특성에 대한 탄소섬유 길이의 영향을 고찰하였다. 매트릭스 precursor로 레졸형의 페놀수지와 강화재로 표면처리를 하지않은 PAN계 단섬유형 탄소섬유를 사용하여 액상함침법으로 1회의 고온열처리 공정과 4회의 탄화공정을 통하여 탄소/탄소복합재료를 제조하였다. Disk-on-disk형의 마모시험기를 통하여 상대 마찰재로 AISI 304 stainliss steel을 사용하여 0.6MPa(61 ${\times}{10^3}$Kg/$m^2$)의 압력과 0.71m/sec의 미끄러짐 속도하에서 측정된 탄소/탄소복합재료의 마찰계수는 0.2-0.3이었다. 마찰계수에 대한 섬유의 길이의 영향은 크게 나타나지 않았지만, 마모 속도는 섬유의 길이가 증가함에 따라 증가하는 경향이 나타났다. 본 실헙 결과를 섬유 강화 플라스틱의 마모 모델을 적용하여 고찰하여 본 결과, 섬유의 길이가 증가함에 따라 탄소/탄소복합재료의 마모 속도가 증가되는 경향은 생성된느 마모조각의 크기가 커기기 때문에 나타난 현상으로 판단되었다.

• 한국세라믹학회지
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• 제30권2호
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• pp.139-147
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• 1993

Two sheets of high strength cement paste using ordinary Portland cement and water soluble polymer (polyacrylamide) were made by kneading with a twin roll mill. A carbon fiber layer out between two sheet of the cement paste, and then carbon fiber reinforced high strength cement composites were prepared by pressing them. The mechanical properties of the composites were investigated through the observation of the microstructure and the application of fracture mechanics. When the carbon fiber was added with 0.2 and 0.3wt% to the composites the flexural strength and Young's modulus were about 110∼116MPa and 74∼77GPa respectively, and critical stress intensity was about 3.14MPam1/2. It can be considered that the strength improvement of high strength cement fiber composites may be due to the removal of macropores and the increase of various fracture toughness effects; grain bridging, frictional interlocking, polymer fibril bridging and fiber bridging.

• Carbon letters
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• 제2권3_4호
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• pp.192-201
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• 2001

The Carbon/Carbon composite was prepared from 3D carbon fiber preform and coal tar pitch as matrix precursor. In order to evaluate of ablative characteristics of the composite, liquid rocket system was employed Kerosene and liquid oxygen was used as propellants, operating at a nominal chamber pressure of 330 psi and a nominal mixture ratio (O/F) of 2.0. The results of an experimental evaluation were that high density composite exhibited high, while low density composites showed low erosion resistance. The erosion rate against heat flux was highly depended on the density of the materials. The morphology of eroded fiber showed differently according to collision angle with heat flux on the composite. The granular matrix which derived from carbonization pressure of 900 bar was more resistance to heat flux than well-developed flow type matrix.

• Carbon letters
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• 제5권1호
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• pp.18-22
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• 2004

The failure behaviours of unidirectional pultruded carbon fiber reinforced polymer (CFRP) composites were monitored by the electrical resistance measurement during tensile loading, three-point-bending, interlaminar shear loading. The tensile failure behaviour of carbon fiber tows was also investigated by the electrical resistance measurement. Infrared thermography non-destructive evaluation was performed in real time during tensile test of CFRP composites to validate the change of microdamage in the materials. Experiment results demonstrated that the CFRP composites and carbon fiber tows were damaged by different damage mechinsms during tensile loading, for the CFRP composites, mainly being in the forms of matrix damage and the debonding between matrix and fibers, while for the carbon fiber tows, mainly being in the forms of fiber fracture. The correlation between the infrared thermographs and the change in the electrical resistance could be regarded as an evidence of the damage mechanisms of the CFRP composites. During three-point-bending loading, the main damage forms were the simultaneity fracture of matrix and fibers firstly, then matrix cracking and the debonding between matrix and fiber were carried out. This results can be shown in Fig. 9(a) and (b). During interlaminar shear loading, the change in the electrical resistance was related to the damage degree of interlaminar structure. Electrical resistance measurement was more sensitive to the damage behaviour of the CFRP composites than the stress/time curve.

• 한국기계가공학회지
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• 제7권4호
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• pp.10-16
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• 2008

This study investigated electromagnetic interference(EMI) shielding effectiveness(SE) of the aluminum film, conductive fabric and nano carbon black carbon fiber reinforced composites. We fabricated carbon fiber reinforced composites filled with nano carbon black where they bonded aluminum film and conductive fabric. The measurements of SE were carried out frequency range from 300MHz to 1.5GHz. It is observed that the SE of the bonded aluminum film and conductive fabric composites is the frequency dependent, increase with the increase in filler nano carbon black content. The aluminum film bonded composites showed higher SE compared to that of carbon black and conductive fabric. The aluminum film bonded epoxy composite was shown to exhibit up to 80dB of SE. The result that aluminum film bonded composite can be used for the purpose of EMI shielding as well as for some microwave applications.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.406-415
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• 2008

Recently, the amount of thermosetting plastic wastes have increased with the production of reinforced plastic composites and causes serious environmental problems. The epoxy composites, one of the versatile thermosetting plastics with excellent properties, cannot be melted down and remolded as what is done in the thermoplastic industry. In this research, a series of experiments that recovers carbon fibers from carbon fiber reinforced epoxy composites for train body was performed. We experimentally examined various decomposition processes and compared their decomposition efficiencies and mechanical property of recovered carbon fibers. For the prevention of tangle of recovered carbon fibers, each composites specimen was fixed with a Teflon supporter and no mechanical mixing was applied. Decomposition products were analyzed by scanning electron microscope (SEM), gas chromatography mass spectrometer (GC-MS), and universal testing machine (UTM). Carbon fibers could be completely recovered from decomposition process using nitric acid aqueous solution, liquid-phase thermal cracking and pyrolysis. The tensile strength losses of the recovered carbon fibers were less than 4%.

• 한국해양공학회지
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• 제14권4호
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• pp.49-55
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• 2000

This study has been investigated to apply fiber reinforced composites instead of asbestos as a friction material. the reinforced used was E-glass fiber and binder resin was phenol having good mechanical properties and heat resistance. And it has been also investigated the effect of molding conditions and some additives such and carbon black, alumina and rubber powder in E-glass fiber/phenol resin composite on the friction on the friction and wear characteristics. As a result, it was found that the molding conditions of E-glass fiber/phenol resin composites for friction materials had to be different from those of phenol resin and was found that the wear rate of E-glass fiber/phenol resin composites added alumina powder was higher than of composites added carbon black in the same wear distance. And it was found that friction coefficient of E-glass/phenol resin composites added carbon black was decreased and that of the composites added the powder of natural rubber and ABS rubber were increased compared to the composites.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 춘계학술발표대회 논문집
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• pp.199-202
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• 2002

Interfacial properties and electrical sensing for fiber fracture in carbon and SiC fibers/epoxy composites were investigated by the electrical resistance measurement and fragmentation test. As fiber-embedded angle increased, interfacial shear strength (IFSS) of two-type fiber composites decreased, and the elapsed time was long to the infinity in electrical resistivity. The initial slope of electrical resistivity increased rapidly to the infinity at higher angle, whereas electrical resistivity increased gradually at small angle. Furthermore, both fiber composites with small embedded angle showed a fully-developed stress whitening pattern, whereas both composites with higher embedded angle exhibited a less developed stress whitening pattern. As embedded angle decreased, the gap between the fragments increased and the debonded length was wider for both fiber composites. Electro-micromechanical technique can be a feasible nondestructive evaluation to measure interfacial sensing properties depending on the fiber-embedded angle in conductive fiber reinforced composites.

• Composites Research
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• 제12권3호
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• pp.75-83
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• 1999

Carbon/Phenolic 및 silica/phenolic 내열 복합재료의 강화재의 종류와 적층방향에 따른 비열, 열확산 계수, 열전도도를 분석하였다. Carbon/Phenolic 및 silica/phenolic 복합재료의 비열은 시차 주사 열량법을 이용하여 측정하였으며, 열확산계수는 레이저 섬광법을 이용하여 laminar와 평행방향과 laminar와 직교방향으로 측정하였다. Carbon/Phenolic 및 silica/phenolic 복합재료의 열확산계수는 온도가 증가함에 따라 감소하였다. Carbon/Phenolic 및 silica/phenolic 복합재료의 열전도도를 밀도, 열확산계수 및 비열을 이용하여 계산하였다. 열전도도는 온도가 증가함에 따라 증가하였으며, carbon/Phenolic의 경우 laminar와 평행방향의 열전도도가 laminar와 직교방향의 열전도도보다 2배 높은 이방성을 나타내었으며 이는 carbon 섬유의 열전도도 이방성 때문으로 해석되었다. 이차원 섬유강화 복합재료의 열전도도를 기지와 강화재의 열전도도와 부피분율을 이용하여 해석하였다. Carbon/Phenolic 및 silica/phenolic 복합재료의 열전도도를 적층방향에 따라 강화재와 기지의 열전도도를 이용하여 해석하여 carbon 섬유와 silica 섬유의 열전도도를 계산하였다. 계산된 섬유의 열전도도와 기지의 열전도도로부터 섬유의 부피분율에 따른 복합재료의 상온열전도도를 예측할 수 있었다.

• Carbon letters
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• 제5권3호
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• pp.108-112
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• 2004

Effect of silicon infiltration on the bend and tensile strength of 2D cross-ply carbon-carbon composites are studied. It is observed that bend strength higher than tensile strength in both types of composite is due to the different mode of fracture and loading direction. After silicon infiltrations bend and tensile strength suddenly decreases of carbon-carbon composites. This is due to the fact that, after silicon infiltration, silicon in the immediate vicinity of carbon forms the strong bond between carbon and silicon by formation silicon carbide and un-reacted silicon as free silicon. Therefore, these composites consist of three components carbon, silicon carbide and silicon. Due to mismatch between these three components secondary cracks developed and these cracks propagate from $90^{\circ}$ oriented plies to $0^{\circ}$ oriented plies by damaging the fibers (i.e., in-situ fiber damages). Hence, secondary cracks and in-situ fiber damages are responsible for degradation of mechanical properties of carbon-carbon composites after silicon infiltration which is revealed by microstructure investigation study by scanning electron microscope.