• 한국산학기술학회논문지
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• 제11권2호
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• pp.426-434
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• 2010

본 논문에서는 충격손상을 갖는 유리섬유강화 복합재료의 강도 저하 특성과 이의 통계적 특성을 실험적으로 평가하였다. 평직 복합재료의 주요 충격손상은 섬유파단과 모재균열로서 이는 층간분리가 주된 충격손상인 일방향 적층복합재료와는 상이한 양상이다. 일방향 적층복합재료에 대하여 제안된 기존의 잔류강도 예측모델을 이용하여 충격손상을 갖는 평직 glass/epoxy 복합재료의 잔류강도를 평가하였다. 그 결과 Avva 및 Caprino의 잔류강도 예측모델은 평직 복합재료의 잔류강도에 대해서도 잘 평가되었다. 또한 유리섬유강화 복합재료의 잔류강도에 대한 통계적 특성 평가를 위한 모델을 제안하였으며, 이를 통한 예측결과는 복합재료의 두께와 관계없이 실험결과를 잘 묘사하였다.

• Elastomers and Composites
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• 제31권1호
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• pp.13-22
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• 1996

In order to Improve the fracture toughness of epoxy resin system, liquid chloroprene rubber(LCR) and liquid butadiene rubber (LBR) which have hydroxy group were used in the brittle epoxy system. Mechanical and toughness characterization of the modified epoxy resins were investigated as a function of liquid rubbers content. Epoxy resins modified with both of the liquid rubbers showed complete phase-separation microstructure : In all of the LCR content, it was observed that the domain size of LCR dispersed in the epoxy matrix ranging from $2{\mu}m\;to\;5{\mu}m$. It was found that fracture toughness, $K_{ic}$, of the modified LCR system was enhanced continuously as increasing LCR content. However around 10phr of LBR system showed maximum fracture toughness. Specifically, when BPA add to the modified LCR system, thermal and mechanical properties increased than neat epoxy. At the same time, fracture toughness was enhanced.

• Carbon letters
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• 제15권1호
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• pp.67-70
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• 2014

In this work, nanocomposites of epoxy resin and chemically reduced graphene oxide (RGO) were prepared by thermal curing process. X-ray diffractions confirmed the microstructural properties of RGO. Differential scanning calorimetry was used to evaluate the curing behaviors of RGO/epoxy nanocomposites with different RGO loading amounts. We investigated the effect of RGO loading amounts on the mechanical properties of the epoxy nanocomposites. It was found that the presence of RGO improved both flexural strength and modulus of the epoxy nanocomposites till the RGO loading reached 0.4 wt%, and then decreased. The optimum loading achieved about 24.5 and 25.7% improvements, respectively, compared to the neat-epoxy composites. The observed mechanical reinforcement might be an enhancement of mechanical interlocking between the epoxy matrix and RGO due to the unique planar structures.

• Transactions on Electrical and Electronic Materials
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• 제18권4호
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• pp.203-206
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• 2017

The effect of the content of microsilica and nanosilica continuously modified with hydroxy silane and epoxy-modified silicone in cycloaliphatic epoxy/microsilica/nanosilica composites (EMNCs) on the mechanical and water repellent properties was evaluated. Surface-modified micro- and nanosilica was well-mixed with a cycloaliphatic epoxy resin in the presence of polyester-modified polydimethylsiloxane (PEM-PDMS) as a dispersing agent using an ultrasonicator. Tensile and flexural tests were carried out using a universal testing machine (UTM). The water repellent property was evaluated by contact angle measurements of water on the composite surface. Tensile strength of the composite could be enhanced by 32.2% up to 91.4 MPa, and the flexural strength was raised to 122.0 MPa, which is 38.8% higher than that of neat epoxy. The contact angle of water on the composite was as high as $104.1^{\circ}$.

• Structural Engineering and Mechanics
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• 제67권5호
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• pp.545-553
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• 2018

Mode II delamination propagation is an important damage mode in laminated composites and this paper aims to investigate the behavior of this damage in laminated composite materials using acoustic emission (AE) technique. Three different lay-ups of glass/epoxy composites were subjected to mode II delamination propagation and generated AE signals were recorded. In order to investigate the propagation of delamination behavior of these specimens, AE signals were analyzed using Wavelet Packet Transforms (WPT) and Fast Fourier Transform (FFT). In addition, conventional AE analyses were used to enhance understanding of the propagation of delamination damage. The results indicate that different fracture mechanisms were the main cause of the AE signals. The dominant mechanisms in all the specimens were matrix cracking, fiber/matrix debonding and fiber breakage, with varying percentage of the damage mechanisms for each lay-up. Scanning Electron Microscopy (SEM) observations were in accordance to the AE results.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
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• pp.83-88
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• 2001

In this study, the tensile and compressive tests of glass fiber epoxy composites were performed to measure the strength variation with respect to strain rates of 1-200 $\textrm{sec}^{-1}$. In addition, tensile and compressive tests of 50-200 $\textrm{sec}^{-1}$ strain rates were conducted at a low temperature ($-60^{\circ}C$) to investigate the effects of temperature on the strength variation. From the test results, it was found that the tensile and compressive strengths increased about 100% and 70%, respectively, at the strain rates of 10-100 $\textrm{sec}^{-1}$ compared to the quasi-static strengths while the strengths were little affected by the environmental temperature variation.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 춘계학술발표대회 논문집
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• pp.105-108
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• 2002

Materials, matrices mixed with various kinds of conductive or magnetic powder, such as ferrite, have been used as the electromagnetic wave absorbing ones, so called RAM(radar absorbing material). The structure that does not only have electromagnetic waves absorbing property like RAM but also supports loads is called RAS(radar absorbing structure). One of the existing manufacturing process of RAS is to compound with conductive powders the glass fiber-reinforced composite with good permeability and the ability to support loads. The process, however, causes a number of problems, such as the degradation in the mechanical properties of the composite, especially, interlamina shear strength. In this study, mechanical properties of glass fabric/epoxy composite containing 7wt% carbon black powders were measured and compared with pure glass fabric/epoxy composites.

• 동력기계공학회지
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• 제7권1호
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• pp.25-33
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• 2003

섬유강화 복합재료의 계면 강도는 강화재와 메트릭스간의 계면특성, 강화용 섬유의 표면처리 및 섬유간의 거리 등에 많은 영향을 받는다. 본 연구에서는 섬유간의 거리가 섬유강화 복합재료의 계면특성에 미치는 영향을 고찰하기 위해, E glass fiber/epoxy 복합재료의 시험편을 제작하고, 섬유의 표면처리 및 섬유파괴가 이웃하는 섬유파괴에 영향을 미치는 거리에 대해 고찰하였다. E glass fiber/epoxy 복합재료의 계면 전단강도는 섬유간 거리 $0{\sim}50{\mu}m$ 사이에서는 섬유의 표면처리와는 관계없이 섬유간 거리가 증가할수록 증가하였고, 섬유간 거리 $50{\mu}m$ 이상에서는 섬유간거리에 관계없이 계면전단강도는 일정하였다.

• Transactions on Electrical and Electronic Materials
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• 제14권1호
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• pp.39-42
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• 2013

The effects of particle size on the mechanical and electrical properties of epoxy/spherical silica composites were studied. The silica particle sizes were varied from 5 to 30 ${\mu}m$ and the filler content was fixed to 60 wt%. Tensile and flexural tests were carried out and the interfacial morphology was observed by scanning electron microscopy (SEM). The electrical insulation breakdown strength was estimated using sphere-sphere electrodes with different insulation thicknesses of 1, 2 and 3 mm. The tensile strength and flexural strength increased with decreasing particle size, while electrical insulation breakdown strength increased with increasing particle size.

• 전기학회논문지
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• 제67권10호
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• pp.1330-1337
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• 2018

In this study, 40, 50, 60, and 70 wt% filler dispersed samples were prepared for the current GIS Spacer or environmentally friendly GIS. In the AC electrical breakdown, EMSC and EMAC decreased with increasing filler content, and EMSC showed better breakdown strength than EMAC. The mechanical properties such as tensile strength and flexural strength of EMSC and EMAC were also increased with increasing filler content. In addition, EMSC results in better mechanical properties than EMAC. The reason for this is considered to be one in which the influence of the interface is important.