• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1990년도 봄 학술발표회 논문집
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• pp.11-15
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• 1990

Results of an experimental study on the manufacture and the mechanical properties of carbon fiber reinforced fly ash-cement composites are presented in this paper. The carbon fiber reinforced fly ash-cement composites using silica powder and a small amount of Ethylene vinyl acetate emulsion are prepared with carbon fiber, foaming agents and curing conditions. As a result, the manufacturing process technology of carbon fiber reinforced fly ash-cement composites is developed. And the mechanical properties such as compressive, tensile and flexural strengths and drying shrinkage of lightweight carbon fiber reinforced fly ash-cement composites are improved by using a small amount of Ethylene vinyle acetate emulsion. The development and applications of precast products and the design systems of lightweight carbon fiber reinforced fly ash-cement composites are expected in the near future.

• Carbon letters
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• 제14권1호
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• pp.58-61
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• 2013

In this work, the effect of catalysts on the mechanical properties of carbon fibers-reinforced epoxy matrix composites cured by cationic latent thermal catalysts, i.e., N-benzylpyrazinium hexafluoroantimonate (BPH) was studied. Differential scanning calorimetry was executed for thermal characterization of the epoxy matrix system. Mechanical interfacial properties of the composites were studied by interlaminar shear strength (ILSS), critical stress intensity factor ($K_{IC}$), and specific fracture energy ($G_{IC}$). As a result, the conversion of neat epoxy matrix cured by BPH was higher than that of one cured by diaminodiphenyl methane (DDM). The ILSS, $K_{IC}$, $G_{IC}$, and impact strength of the composites cured by BPH were also superior to those of the composites cured by DDM. This was probably the consequence of the effect of the substituted benzene group of BPH catalyst, resulting in an increase in the cross-link density and structural stability of the composites studied.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1991년도 가을 학술발표회 논문집
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• pp.99-106
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• 1991

Result of an experimental study on the manufacture, the mechanical properties and waterightness of pitch-based carbon fiber reinforced fly ash.cement composites are presented in this paper. The carbon fiber reinforced fly ash.cement composites using early strength cement, silica powder and a small amount of stylene butadiene rubber latex are prepared with carbon fiber, foaming agents and mixing conditions. As a result, the mechanical and plysical properties such as compresive, tensile and flectural strengths, watertightness and cement composites are improved by using a small amount of stylene butadiene rubber latex.

• 한국재료학회지
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• 제20권3호
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• pp.148-154
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• 2010

It is necessary to develop new methods to prevent catastrophic failure of structural material in order to avoid accidents and conserve natural and energy resources. Design of intelligent materials with a self-diagnosing function to prevent fatal fracture of structural materials was achieved by smart composites consisting of carbon fiber tows or carbon powders with a small value of ultimate elongation and glass fiber tows with a large value of ultimate elongation. The changes in electrical resistance of CF-GFRP/GFRP (carbon fiber and glass fiber-reinforced plastics/glass fiber-reinforced plastics) composites increased abruptly with increasing strain, and a tremendous change was seen at the transition point where carbon fiber tows were broken. Therefore, the composites were not to monitor damage from the early stage. On the other hand, the change in electrical resistance of CP-GFRP/GFRP (carbon powder dispersed in glass fiber-reinforced plastics/glass fiber-reinforced plastics) composites increased almost linearly in proportion to strain. CP-GFRP/GFRP composites are superior to CF-GFRP/GFRP composites in terms of their capability to monitor damage by measuring change in electrical resistance from the early stage of damage. However, the former was inferior to the latter as an application because of the difficulties of mass production and high cost. A method based on monitoring damage by measuring changes in the electrical resistance of structural materials is promising for improved reliability of the material.

• Composites Research
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• 제34권2호
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• pp.82-87
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• 2021

The mechanical properties of carbon fiber-reinforced epoxy composites (CFRPs) are greatly dependent on the interfacial adhesion between the carbon fibers and the epoxy matrix. Introducing nanomaterial reinforcements into the interface is an effective approach to enhance the interfacial adhesion of CFRPs. The main purpose of this work was to introduce graphitic nanofiber (GNFs) between an epoxy matrix and carbon fibers to enhance interfacial properties. The composites were reinforced with various concentrations of GNFs. For all of the fabricated composites, the optimum GNF content was found to be 0.6 wt%, which enhanced the interlaminar shear strength (ILSS) and fracture toughness (KIC) by 101.9% and 33.2%, respectively, compared with those of neat composites. In particular, we observed a direct linear relationship between ILSS and KIC through surface free energy. The related reinforcing mechanisms were also analyzed and the enhancements in mechanical properties are mainly attributed to the interfacial interlocking effect. Such an effort could accelerate the conversion of composites into high performance materials and provide fundamental understanding toward realizing the theoretical limits of interfacial adhesion and mechanical properties.

• 한국해양공학회지
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• 제29권2호
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• pp.186-190
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• 2015

$TiO_2$ nanoparticles can be used to improve the performance of carbon fiber-reinforced epoxy resin composites. In this study, the effect of the size of $TiO_2$ nanoparticles on the mechanical properties of carbon fiber-reinforced epoxy resin composites was investigated. The size of the $TiO_2$ nanoparticles was easily controlled using heat treatment. The size of the $TiO_2$ nanoparticles for this study were20nm, 100nm, and 200nm. Three types of carbon fibers with different diameters were also used in this study. The carbon fiber-reinforced epoxy resin composites with 20-nm $TiO_2$ powder showed the highest tensile strength compared to the other types of CFRP, regardless of the fiber maker or fiber diameter. The size of the $TiO_2$ powder and the diameter of the carbon fiber strongly affected the interfacial properties of all kinds of CFRP in this study.

• Carbon letters
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• 제9권4호
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• pp.316-323
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• 2008

The factors that influence ablation resistance in fiber composites are properties of the reinforced fiber and matrix, plugging quantity of fiber, geometrical arrangement, crack, pore size, and their distributions. To examine ablation resistance according to distribution of crack and pore size that exist in carbon/carbon composites, this study produced various sizes of unit cells of preforms. They were densified using high pressure impregnation and carbonization process. Reinforced fiber is PAN based carbon fiber and composites were heat-treated up to $2800^{\circ}C$. The finally acquired density of carbon/carbon composites reached more than $1.932\;g/cm^3$. The ablation test was performed by a solid propellant rocket engine. The erosion rate of samples is below 0.0286 mm/s. In conclusion, in terms of ablation properties, the higher degree of graphitization is, the more fibers that are arranged vertically to the direction of combustion flame are, and the less interface between reinforced fiber bundle and matrix is, the better ablation resistance is shown.

• 한국세라믹학회지
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• 제37권6호
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• pp.569-575
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• 2000

Fabrication of carbon fiber reinforced composites was carried out by hand lay-up method. Carbon nanofibers and SiC nanofibers were used as filler in the composites fabrication. Carbon nanofibers, one of the new carbon materials, have 5∼500 nm in diameter and 5-10 nm in length. SiC nanofibers were modified by silicon monoxide vapor with carbon nanofibers. The composites were carbonized at 1000$^{\circ}C$ in a nitrogen atmosphere, and then densified by molten pitches impregnated in vacuum. Multiple cycles of liquid pitch impregnation and carbonization were carried out to obtain a desired density. The composites were characterized by density, microstructure. The inter-laminar shear strength (ILSS) test was performed for mechanical properties. For the new application, the microwave reflective proeprty of composites was investigated. Dielectric constant and permeability spectrum were measured in 12∼18 GHz frequency ranges. On the basis of the wave propagation theory in a lossy media, the reflection loss from the composite inter-layer was predict as a function of frequency.

• Carbon letters
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• 제16권2호
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• pp.67-77
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• 2015

Carbon fibers (CFs) have a unique combination of properties which allow them to be widely used as reinforcing materials in advanced polymer composites. The mechanical properties of CF-reinforced polymer composites are governed mainly by the quality of interfacial adhesion between the CFs and the polymer matrix. Surface treatments of CFs are generally carried out to introduce chemical functional groups on the fiber surfaces, which provide the ability to control the surface characteristics of CFs. In this study, we review recent experimental studies concerning various surface treatment methods for CFs. In addition, direct examples of the preparation and properties of CF-reinforced thermosetting composites are discussed.

• Elastomers and Composites
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• 제47권1호
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• pp.65-74
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• 2012

최근 전세계적으로 자원 고갈로 인한 에너지 절약과 환경 문제에 관한 규제 강화는 환경 친화적인 소재 개발의 필요성을 가속화시키고 있다. 이러한 추세는 자동차 산업을 포함한 운송 산업도 예외가 아니다. 또한, 기본적으로 단순히 성능이 좋으면서도 값이 저렴한 제품이 아니라, 소비자와 사회의 요구에 부합되는 고기능성 소재의 개발이 필요하다. 이에 부합하는 소재로는 최근 운송 수단의 경량화를 위하여 많은 연구가 진행중인 탄소섬유 복합재료라할 수 있다. 최근 탄소섬유 복합재료는 자동차의 경량화를 위해 차체 및 부품 등 다양한 부분에 적용됨에 따라 그 수요는 크게 증가하고 있고, 차량에 적용시 차체 중량감소에 따른 제동, 조향, 내구 및 연비향상과 이에 따른 에너지 절약 및 이산화탄소 배출을 최소화 하는 장점을 갖는다. 따라서, 본고에서는 자동차의 경량화를 위한 탄소섬유 복합재료의 필요성과 더불어 탄소섬유 복합재료의 기술동향과 나아가야 할 방향에 대하여 살펴보도록 하겠다.