• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 추계학술발표대회 논문집
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• pp.56-59
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• 2002

This paper presents a study on the permittivities of the E-glass fabric/epoxy composite laminates containing carbon black dispersions at microwave frequency. Measurement showed that the complex permittivities of the composites depend strongly on the natures and concentrations of the carbon black dispersion. A new scheme to obtain a mixing law for the estimation of complex permittivity is proposed. The experimental values of the complex permittivities were compared to those calculated. Simultaneously, the complex permittivity of carbon black itself was also calculated by the scheme.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2005년도 춘계학술발표대회 논문집
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• pp.111-115
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• 2005

Recently, natural fibers draw much interests in composite industry due to low cost, light weight, and environment-friendly characteristics compared with glass fibers. In this study, mechanical properties were evaluated for two extreme cases of jute fiber orientations, i.e. the unidirectional yarn composites and the felt fabric composites. Samples of jute fiber composites were fabricated by RTM process using epoxy resin, and tensile, compression, and shear tests were conducted. As can be expected, unidirectional fiber specimens in longitudinal direction showed the highest strength and modulus. Compared with glass/epoxy composites of the similar fabric architecture and fiber volume fraction, the tensile strength and modulus of jute felt/epoxy composites reached only 40% and 50% levels. However, the specific tensile strength and modulus increased to 80% and 90% of the glass/epoxy composites. The main reason for the poor mechanical properties of jute composites is associated with the weak interfacial bonding between fiber and matrix. The effect of surface treatment of jute fibers on the interfacial bonding will be examined in the future work.

• Composites Research
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• 제17권2호
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• pp.1-8
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• 2004

본 논문은 겹판 스프링의 정적 스프링 상수를 가지고 복합재료 데이퍼 스프링을 최적설계 하였다. 두께와 폭을 설계변수로 실정하였다. 회귀모형의 목적함수는 상용 해석 프로그램을 통해 얻었다. 회귀모형의 함수를 가지고 회귀계수를 계산한 후, DOT를 이용하여 최적해를 구하였다. 설계에 이용된 복합재료로는 E-glass/epoxy와 carbon/epoxy를 선정하였고 겹판 스프링과 비교 해석하였다. 그 결과 정적 스프링 상수는 최적화된 복합재료 스프링들과 겹판 스프링이 1％내로 일치함을 보였다.

• Tribology and Lubricants
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• 제36권3호
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• pp.133-138
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• 2020

In this paper, we present an experimental investigation of the friction coefficient and wear area change of carbon/epoxy and E-glass/epoxy composites depending on the fiber direction (0°/90°). We compared the results of the case where the sliding direction is parallel to the fiber direction (0°) with that of the case where it is perpendicular to the fiber direction (90°). The ball-on-plate wear test equipment was used to cause wear in both directions. Two types of specimens were prepared with thicknesses of 3 mm-one made of carbon fiber reinforced plastic composite (CFRP) and the other of glass fiber reinforced plastic composite (GFRP). A normal force of 20 N was applied to the specimen and the sliding speed was 10 mm/s and the sliding distance was set to 20 m to perform the wear test. The CFRP demonstrates superior tribological characteristics compared to the GFRP. This outcome is attributed to graphitization of carbon, which serves as solid lubricating particles. In addition, both CFRP and GFRP are worn more in the 90° direction than in the 0° direction. This is due to the greater occurrence of fiber breakage and separation in the 90° direction than in the 0° direction. This study is expected to be utilized as basic data for understanding the friction and wear characteristics of CFRP and GFRP composites along the fiber direction and to apply the appropriate material.

• Advances in materials Research
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• 제6권2호
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• pp.155-168
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• 2017

The terrorist attacks and dangers by bomb blast have turned into an emerging issue throughout the world and the protection of the people and structures against terrorist acts depends on the prediction of the response of structures under blast and shock load. In this paper, behavior of aluminum and unidirectionally reinforced E-Glass Epoxy composite plates with and without focal circular holes subjected to shock loading has been identified. For isotropic and orthotropic plates (with and without holes) the classical normal mode approach has been utilized as a part of the processing of theoretical results. To obtain the accurate results, convergence of the results was considered and a number of modes were selected for plate with and without hole individually. Using a shock tube as a loading device, tests have been conducted to composite plates to verify the theoretical results. Moreover, peak dynamic strains, investigated by experiments are also compared with the theoretical values and deviation of the results are discussed accordingly. The strain-time histories are likewise indicated for a specific gauge area for aluminum and composite plates. Comparison of dynamic-amplification factors between the isotropic and the orthotropic plates with and without hole has been discussed.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2005년도 춘계학술발표대회 논문집
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• pp.141-145
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• 2005

Since the electromagnetic properties of fiber reinforced polymeric laminate composite can be tailored effectively by adjusting its composition and regulating the stacking sequence, it is plausible material for fabricating the radar absorbing structures (RAS) of desired performance. In order to design the effective electromagnetic wave (EM) absorber with the fiber reinforced polymeric laminate composite, its electromagnetic characteristics should be available and could be regulated easily in the target frequency bands. In this study, dielectric characteristics of the E-glass/epoxy laminate composites were measured by the free space method in the X-band frequency range ($8.2\;{\sim}\;12.4\;GHz$). In order to describe the dielectric behavior of laminate composites of arbitrary stacking sequences, the equivalent circuit model and the laminating equations for estimating dielectric properties were proposed, and experimentally verified. From the comparison of the predicted and measured data, the proposed method predicted well the experimentally measured data.

• 한국가스학회지
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• 제13권4호
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• pp.15-21
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• 2009

섬유강화 복합재료는 비강성과 비강도등의 우수한 기계적 성질을 나타내므로 구조물의 경량화가 요구되는 여러 산업분야에서 널리 사용되고 있다. 이러한 복합재를 이용한 압력용기는 무게를 경량화함으로써 에너지를 절약할 수 있고 강한 내식성을 가지고 있기 때문에 장기간 사용에 유리하다. 본 연구에서는 유한요소법과 ANSYS 반응표면법을 이용하여 안정성 판단의 기준으로 Von-mises 항복 기준, Tasi-hill이론, 응력비를 만족시킬 수 있는 E-glass/epoxy로 필라멘트 와인딩된 CNG차량복합재 압력용기 적층판의 최적설계 모듈을 개발하였다.

• Composites Research
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• 제29권6호
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• pp.388-394
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• 2016

Fiber reinforced plastic (FRP) composites have drawn increasing attentions worldwide for decades due to its outstanding properties. Stress concentration factor (SCF) as an essential parameter in materials science are critically considered in structure design and application, strength assessment and failure prediction. However, investigation of stress concentration in FRP composites has been rarely reported so far. In this study, three resource-conserving analyses (Isotropic analysis, Orthotropic analysis and Finite element analysis) were introduced to plot the $K_T^A-d/W$ curve for E-glass/epoxy composite plate with the geometrical defect of circular hole placed centrally. The plates were loaded to uniaxial direction for simplification. Finite element analysis (FEA) was carried out via ACP (ANSYS composite prepost module). Based on the least squares method, a simple expression of fitting equation could be given based on the simulated results of a set of discrete points. Finally, all three achievable solutions were presented graphically for explicit comparison. In addition, the investigation into customized efficient SCFs has also been carried out for further reference.

• Composites Research
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• 제16권2호
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• pp.48-53
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• 2003

본 논문에서는 카본 블랙의 함유율에 따른 유리섬유/에폭시 직조 복합재료 적층판의 유전율에 대한 실험 및 예측방법에 대한 연구를 수행하였다. 유전율 측정은 5 GHz∼18 GHz의 주파수 영역에서 수행하였으며, 복합재료의 유전율은 카본 블랙의 함유율과 주파수의 함수로 얻을 수 있었다. 카본 블랙의 함유율에 따른 복합재료의 유전율을 모사하는 혼합법칙을 얻기 위한 새로운 방법이 제시되었으며. 이 방법에서는 실험적으로 얻기 어려운 카본 블랙 자체의 유전율도 얻을 수 있다. 혼합법칙으로 계산된 복합재료 유전율 결과는 실험적으로 얻은 유전율을 비교적 잘 모사하는 결과를 얻을 수 있었다.

• E2M - 전기 전자와 첨단 소재
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• 제7권6호
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• pp.527-533
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• 1994

In this study, it was studied on dielectric breakdown strength and thennostability properties due to the structure variation of matrix resin and treatment of coupling agent of epoxy insulating materials. The interpenetrating network structure was formed by simultaneous heating curing the epoxy resin with single network structure and the methacrylic acid resin. Also inner structure was observed and the glass transition temperature was measured on these three type specimens. Dielectric breakdown properties were investigated by applying DC, AC and impulse voltage. As a result, the glass transition temperature and the dielectric breakdown strength of specimen with interpenetrating network structure was more higher than another two type specimens.