• Macromolecular Research
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• 제8권4호
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• pp.153-164
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• 2000

By electrodeposition (ED) using a monomeric- and two polymeric coupling agents, the interfacial shear strength (IFSS) of carbon fiber/epoxy composites was investigated by fragmentation test. ED results were compared with the dipping and the untreated cases under dry and wet conditions. Multi-fiber composites (MFC) were used for the direct comparison for the untreated and the treated cases. Various treating conditions including time, concentration and temperature were evaluated, respectively. Under dry and wet conditions ED treatment exhibited much higher IFSS improvement compared to the dipping and the untreated cases. Monomeric- and polymeric coupling agents exhibited the comparative IFSS improvement. Adsorption mechanism between coupling agents and carbon fiber was analyzed in terms of the electrolyte molecular interactions during ED process based on to the chain mobility. The microfailure modes occurring from the fiber break, matrix and interlayer cracks were correlated to IFSS.

• 한국정밀공학회지
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• 제12권8호
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• pp.27-38
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• 1995

For solving troubles happened during the drilling process with carbon fiber epoxy composite materials(CFRP) by using HSS drill, a few types of diamond gift electroplated drills are manufactured, and machinability of these drills is experimented with a variety of cutting speed and feed rate. These drills have some advantages of good wear resistant and the conception of grinding process. As a result, using of these drills improves both troubles being caused by tool wear and damage of exit surface depending on fiber stacking angle. It is desirable that cutting conditions for the cutting thickness per revolution must be set under 0.01mm when the size of a diamond grit is # 60 .approx. 80.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2005년도 추계학술발표대회 논문집
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• pp.153-156
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• 2005

Nondestructive sensing of electrospun PYDF web and multi-wall carbon nanotube (MWCNT)/epoxy composites were investigated using electro-micromechanical technique. Electrospinning is a technique used to produce micron to submicron diameter polymeric fibers. Electrospun PVDF web was also evaluated for the sensing properties by micromechanical test and by measurement electrical resistance. CNT composite was especially prepared for high volume contents, 50 vol% of reinforcement. Electrical contact resistivity on humidity sensing was a good indicator for monitoring as for multifunctional applications. Work of adhesion using contact angle measurement was studied to correlate acid-base surface energy between carbon fiber and CNF composites, and will study furher for interfacial adhesion force by micromechanical test.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.593-597
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• 2005

It is generally accepted that fracture toughness of fiber-reinforced polymer composites is affected by loading rate in an atmospheric presure condition. For a present study, the loading rate effect on the fracture toughness of fiber-reinforced laminated composites in the hydrostatic pressure condition was investigated. For this purpose, fracture tests have been conducted using carbon/epoxy composites applying three steps of the strain rate at 270 MPa hydrostatic pressure condition. The loading rates applied were 0.05%/sec, 0.25%/sec, and 0.55%/sec. Fracture toughness was determined from the work factor approach as a function of applied loading rate. The result showed that fracture toughness decreased as the loading rate increased. Specifically, the fracture toughness decreased 12% as the loading rate increased from 0.05%/sec to 0.55%/sec.

• 한국정밀공학회지
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• 제21권4호
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• pp.148-153
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• 2004

It is well-known that the mechanical behavior of fiber-reinforced composites under hydrostatic pressure environment is different from that of atmospheric pressure environment. It is also known that the mechanical behavior of fiber-reinforced composites is affected by a strain rate. In this work, we investigated the effect of strain rate on the compressive elastic modulus, fracture stress, and fracture strain of carbon/epoxy composites under hydrostatic pressure environment. The material used in the compressive test was unidirectional carbon/epoxy composites and the hydrostatic pressures applied was 270㎫. Compressive tests were performed applying three strain rates of 0.05％/sec, 0.25％/sec, and 0.55％/sec. The results showed that the elastic modulus increased with increasing strain rate while the fracture stress was little affected by the strain rate. The results also showed that the fracture strain decreased with increasing strain rate.

• 한국해양공학회지
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• 제7권1호
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• pp.25-32
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• 1993

In composite materials, the fracture perpendicular to the fiber direction usually shows a non-linear behavior accompannying blunting and plastic deformation around the crack tip. In this study, the fracture thoughness in random short fiber SMC composite material and Carbon/Epoxy composite material is estimated by the A.M.(Area Method) and the G.L.M.(Generalized Locus Method) which can determine a stable total energy release rate(G$_T$) not only in highly elghly elastic material but also in highly non-linear materials.

• Composites Research
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• 제16권2호
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• pp.62-67
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• 2003

Microdroplet 시험법과 전기저항 측정을 이용하여 탄소섬유강화 epoxy-AT-PEI 복합재료의 손상 감지능 및 계면물성평가에 대한 연구를 수행하였다. AT-PEI 함량이 증가함에 따라 기지재료의 파괴인성은 증가하였으며, 이로 인한 에너지흡수 메커니즘에 의해서 계면전단강도 역시 증가하였다. Microdroulet 시험에서 순수 에폭시는 취성파괴 현상을 그리고 15 phr AT-PEI의 경우에는 파괴인성의 증가로 인해 연성 파단 현상을 관찰할 수 있었다. 경화 후에 열 수축에 의한 전기저항 변화는 AT-PEI 함량 증가에 따라 증가하였으며. 가변하중 하에서 순수 에폭시에 함침된 탄소섬유의 같은 응력까지의 도달시간과 기울기는 15 phr AT-PEI의 경우보다 더 빠르고 높았다. 경화과정과 가역적인 하중 하에서의 전기저항 측정으로부터 얻은 결과는 기지재료의 파괴인성과 잘 일치하였다.

• 한국염색가공학회지
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• 제27권1호
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• pp.11-17
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• 2015

Recently, super fiber reinforced composite materials are widely used in many industries due to high mechanical properties. In this study, 2 different types of composite materials were manufactured in order to compare their mechanical properties. Carbon and Aramid fibers were used for reinforcement materials and Bisphenol-A type epoxy resin was for matrix. Two kinds of fiber-reinforced materials were manufactured by RIM(Resin Injection Molding) method. Before manufacturing composite materials, the optimal manufacturing and curing process condition were established and the ratio of reinforcement to epoxy resin was discussed. FT-IR analysis was conducted to clarify the structure of epoxy resin. Thermal and mechanical property test were also carried out. The cross-section of composite materials was observed using a scanning electron microscope(SEM).

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2003년도 추계학술발표대회 논문집
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• pp.111-114
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• 2003

Thermosets are highly cross-linked polymers with a three-dimensional molecular structure. The network structure gives rise to mechanical properties, however, one major drawback of thermosets, which also results from their network structure, is their poor resistance to impact and to crack initiation. In this study, to solve this problem, the reactive thermoplastics such as amine terminated polyetherimide (ATPEI), ATPEI-CTBN-ATPEI(ABA) triblock copolymer, CTBN-ATPEI(AB) diblock copolymer, and carboxyl group modified ATPEI was synthesized, after that blended with epoxy resin, and the carbon fiber reinforced composites were fabricated. The impact load, energy, and delamination were investigated by using drop weight impact test and C-scan test. As a results, the ABA/epoxy blend system showed good impact properties.

• 유변학
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• 제3권1호
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• pp.22-29
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• 1991

In an effort to predict the long term durability of carbon fiber/epoxy composites in a space environ-ment interlaminar shear strength (ILSS) of the composites was measured as a function of 0.5 MeV electron radiation dosage. For the ILSS measurements a notch method (ASTM D3846) was used with and without side-supports. the supports were used to prevent peeling or bending during the test. The ILSS of both T300/ 5209 longitudinal composite system increases monotonically with radiation when the test is corried out without the support the ILSS of the composites increases initially but then decreases with further radiation. It is also observed that the ILSS of the unsupported case is much lower than that of the supported case. Measurement of epoxy modulus shows that the elastic modulus increases monotonically with radiation. But the breaking strength of the epoxy decreases with radiation. Electron Spectroscopy for Chemcal Analysis shows that the oxygen contents at both the pure epoxy surface and the composite fracture surface increase with radiation dose resulting in the increase of polarity at the interfacial region. This may be a supporting evidence for the increase in the ILSS of the composites.