• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2010년도 춘계학술대회 논문집
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• pp.1255-1256
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• 2010

• Carbon letters
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• 제14권1호
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• pp.22-26
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• 2013

The effects of heat treatment temperature (HTT) of polyacrylonitrile-based carbon fiber (CF) on the mechanical, thermal, and tribological properties of C/C composites were investigated. It was found that HTT (graphitization) of CF affects the thermal conductivity and mechanical and tribological characteristics of C/C composites. Thermal treatment of fibers at temperatures up to $2800^{\circ}C$ led to a decrease of the wear rate and the friction coefficient of C/C composite-based discs from 7.0 to 1.1 ${\mu}m$/stop and from 0.356 to 0.269, respectively. The friction surface morphology and friction mechanism strongly depended on the mechanical properties of the CFs. The relief of the friction surface of composites based on CFs with final graphitization was also modified, compared to that of composites based on initial fibers. This phenomenon could be explained by modification of the abrasive wear resistance of reinforcement fibers and consequently modification of the friction and wearing properties of composites. Correlation of the graphitization temperature with the increased flexural and compressive strength, apparent density, and thermal conductivity of the composites was also demonstrated.

• Advances in aircraft and spacecraft science
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• 제4권5호
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• pp.573-583
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• 2017

This paper presents a first step towards the understanding of water diffusion in RTM textile composite materials for aircraft applications and focuses on the development of experimental and numerical approaches to characterize the diffusion kinetics within the material. The method consists in making samples which are representative of the materials architecture and carrying out gravimetric tests on such samples. Analysis of results with the aid of a diffusion model reconstructing the architecture of the samples helps identifying the diffusion behaviour of the material.

• 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.

• Macromolecular Research
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• 제9권1호
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• pp.20-29
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• 2001

Interfacial adhesion and nondestructive behavior of electrodeposited (ED) carbon fiber rein-forced composites were evaluated using electro-micromechanical techniques and acoustic emission (AE). The interfacial shear strength (IFSS) of the ED carbon fiber/epoxy composites was higher than that of the untreated fiber. This might be expected because of the possibility of chemical or hydrogen bonding in an electrically adsorbed polymeric interlayer. The logarithmic electrical resistivity of the untreated single-carbon fiber composite increased suddenly to infinity when fiber fracture occurred, whereas that of the ED composite increased relatively gradually to infinity. This behavior may arise from the retarded fracture time due to enhanced IFSS. In single- and ten-carbon fiber composites, the number of AE signals coming from interlayer failure of the ED carbon fiber composite was much larger than that of the untreated composite. As the number of the each first fiber fractures increased in the ten-carbon fiber composite, the electrical resistivity increased stepwise, and the slope of the logarithmic electrical resistance increased.

• Elastomers and Composites
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• 제46권2호
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• pp.118-124
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• 2011

최근 모든 산업분야에서 기존 소재의 물성을 뛰어넘는 우수한 기계적 특성과 기능적 특성을 만족하는 새로운 소재에 대한 필요성이 점점 증가하고 있으며, 특히 연료 절감과 이산화탄소($CO_2$)와 같은 온난화 가스 배출의 절감을 통한 환경보호가 요구됨에 따라 우주항공 산업에서는 신규 소재를 통한 구조체 경량화에 대한 중요성이 더욱 강조되고 있다. 또한, 신규 소재의 다양한 응용을 위하여 우수한 기계적 물성뿐만 아니라 여러가지 특성에 부합되는 고기능성 맞춤형 재료의 개발은 현재의 재료 과학기술의 최우선적인 목표이며, 이러한 맞춤형 재료에 가장 근접한 소재는 탄소섬 유강화 복합재료라 할 수 있다. 실제로 최근 탄소섬유강화 복합재료는 항공기 경량화를 위한 필수적인 물질로서 그 수요는 크게 증가하고 있다. 따라서, 본고에서는 항공기의 경량화를 위한 탄소섬유강화 복합재료의 필요성과 더불어 탄소섬유강화 복합재료의 기술동향에 대하여 중심으로 살펴보도록 하겠다.

• 항공우주시스템공학회지
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• 제15권2호
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• pp.16-25
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• 2021

Reliability of fatigue strength on Aircraft Composites(GFRP) Structures was assessed in this paper. Fatigue strength of GFRP was used through the existing fatigue test data with Monte Carlo method. The S_a-N_f curve of composites fatigue strength was assumed as normal distribution and reliability was analyzed using SSIT model. Fatigue stress was designed IAW ASTM F3114-15 with special safety factor of S_sf=1.2~2.0. Reliability was calculated by analytic method and FORM. Sensitivity for the effect of mean and standard deviation of fatigue strength as well as fatigue stability was evaluated. This result can be usefully applied to reliability and fatigue design for composite structures of light weight aircraft.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
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• pp.258-262
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• 2001

The contact resistivity was correlated with IFSS and microfailure modes in conductive fiber/cement composites electro-pullout and AE. As IFSS increased, the number of AE signals increased and the contact resistivity increased latter to the infinity. In dual matrix composite (DMC) test and AE, the number of signals with high amplitude and energy in g]ass fiber composite is significantly larger than that of no-fiber composite. Many vertical and diagonal cracks were observed in glass fiber and no-fiber composite under tensile test, respectively. Electro-micromechanical technique and AE can be used efficiently for sensitive nondestructive (NDT) evaluation and to detect microfailure mechanisms in various conductive fibers reinforced brittle and nontransparent cement composites.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 1999년도 추계학술발표대회 논문집
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• pp.28-31
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• 1999

Carbon fiber/epoxy composites using electrodeposited monomeric and polymeric coupling agents were compared with the dipping and the untreated cases. Treating conditions such as time, concentration and temperature were optimized. Four-fibers embedded micro-composites were prepared for fragmentation test. Interfacial properties of four-fiber composites with different surface treatments were investigated with simultaneous acoustic emission (AE) monitoring. The microfailure mechanisms occurring from fiber break, matrix and interlayer crackings were examined by AE parameters and an optical microscope. It was found that interfacial shear strength (IFSS) of electrodeposited carbon fibers was much higher than the other cases under dry and wet conditions. Well separated and different-shaped AE groups occurs for the untreated and ED treated case, respectively.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2000년도 추계학술발표대회 논문집
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• pp.79-83
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• 2000

Interfacial and microfailure properties of carbon liber/bismaleimide (BMI) composites were evaluated using both tensile fragmentation and compressive Broutman tests with acoustic emission (AE). Since BMI is rather difficult matrix to apply for the conventional fragmentation test because of its too low elongation and too brittle and high modulus properties, dual matrix composite system was applied. After carbon fiber/BMI composite was prepared for rod shape by controlling differing curing stage, composites rod was embedded in toughened epoxy as outer matrix. The typical microfailure modes including fiber break, matrix cracking, and interlayer failure were observed during tensile testing, whereas the diagonal slippage in fiber ends was observed during compressive test. On the other hand, AE amplitudes of BMI matrix fracture were higher than carbon fiber tincture under tensile test because BMI matrix has very brittle and high modulus. The waveform of signals coming from BMI matrix fractures was consistent with AE amplitude result under tensile tests.