• 대한금속재료학회지
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• 제50권10호
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• pp.729-734
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• 2012

This study investigated the effect of water absorption on the tensile properties of carbon-glass/epoxy hybrid composites at room temperature and $-30^{\circ}C$. To investigate the effect of the position of glass fabric in the hybrid composite on the tensile properties, the stacking pattern of the fiber fabrics for reinforcing was created in three different ways: (a) glass fabrics sandwiched between carbon fabrics, (b) carbon fabrics sandwiched between glass fabrics and (c) alternative layers of carbon and glass fabrics. They were manufactured by a vacuum-assisted resin transfer molding (VARTM) process. The results showed that there was surprisingly little difference in tensile strength at the two different temperatures with dry and wet conditions. However, the water absorption into the hybrid system affected the tensile properties of the hybrid composites at RT and $-30^{\circ}C$. When the glass fabrics were at the outermost layers, the hybrid composite had the lowest tensile properties. This is attributed to the fact that the composite had a relatively high water absorption rate.

• 대한기계학회논문집
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• 제17권5호
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• pp.1106-1114
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• 1993

본 연구에서는우수한 섬유강화 고분자복합판의 제조 및 개량을 섬유구조의 분리. 배향의 관점에서 연구한다. 유리섬유매트는 유리섬유를 50mm의 길이로 균일하 게 절단하여 공기중에서 분산시켜 6~7mm두께로 만들고,이 유리섬유매트를 바늘의 종류와 스트레칭 횟수에 따라 니들펀칭하여 유리섬유의 매트구조를 변화시킨다. 유리 섬유의 매트구조 별로 모재와 적층시킨 다음 열압축프레스를 사용하여 1차로 시이트를 제작하고, 이 제작된 시이트를 가열로로 가열하여 2차 고온압축 프레스성형한다. 이 때 섬유와 모재의 분리 및 배향의 상관관계를 나타내는 상관계수를 구하고, 이 계수에 미치는 매트 구조의 영향에 대한 실험결과를 보고한다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 B
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• pp.581-583
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• 1993

One of the principal problems encountered in the use of fiber reinforced composites is to establish an active fiber surface to achieve maximum adhesion between resin and fiber surface. In order to improve the interface bonding, the surface of glass fiber should be treated with silane coupling agent in ordinary composite manufacturing processes. However, the price of the coupling agent is very high and in the treating process voids are formed, which decreasees electrical and mechanical strength. We want to develope new process that will overcome the disadvantage of the coupling agent and achieve maximum adhesion at the interface between resin and fiber by active plasma treatment on the glass fiber surface. In this study, we investigate the improvement of contact angle on the glass plate surface as the first step in developing new GFRP.

• 한국기계가공학회지
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• 제20권10호
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• pp.72-79
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• 2021

A circular saw is an effective tool for cutting glass and carbon-fiber hybrid composites. This study investigated tool wear and cut quality when reusing saw blades. The carbide saws wear four times faster than the new ones, and polycrystalline diamond (PCD) is very resistant to tool wear, except at the end of its lifespan. The cut cross-section quality is affected by the blade type, tool wear, and spindle speed. Alternate top bevel (ATB)-type blades are suitable for cutting fiber-reinforced plastics, but triple-chip grind (TCG)-type blades are unsuitable because they cause fiber-pullout defects. Tool wear and low spindle speeds increase the occurrence of arc scratches, due to the rear saw blade. A microscopic examination showed that the burr, which is a mixture of fiber chips and epoxy matrix, was bonded on top, and glass-fiber delamination occurred on the bottom glass-fiber-reinforced polymer (GFRP) surface.

• Composites Research
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• 제30권3호
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• pp.188-192
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• 2017

The mechanical properties of composites are significantly affected by external environment. It is essential to understand the degradation of material performance and judge the material's lifetime in advance. In the current research, changes in mechanical properties of glass fiber and unsaturated polyester composite materials (GFRP, Glass fiber reinforced plastic) were investigated under different bending stress and submerged in hot water at a temperature of $80^{\circ}C$. Loading time of 100 H (hours), 200 H, 400 H, 600 H, 800 H for testing under stresses equal to 0% (stress-free state), 30%, 50% and 70% of the ultimate strength was applied on the GFRP specimens. From the values of bending stress, obtained from three-point bending test, fracture energy, failure time, and life curve were analysed. Moreover, a normalized strength degradation model for this condition was also developed. It was observed that within 100 H, the decline rate of the bending strength was proportional to the pressure.

• 한국초전도ㆍ저온공학회논문지
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• 제25권3호
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• pp.43-48
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• 2023

Polymer composites, especially glass fiber reinforced polymer (GFRP) are finding ever-increasing applications in areas such as superconductivity, space technology, cryogenic rocket engines, and cryogenic storage vessels. Various components made of polymer composites are much lighter than their metallic counterparts but have equivalent strength for ultra-low temperature applications. In this paper, we have investigated the tensile properties of an indigenously prepared unidirectional cylindrical hollow composite tube for its use as a neck of the cryogenic vessel. XRD and SEM of the tube are completed before cryogenic conditioning to ascertain the fiber and resin distribution in the matrix. The result shows that for composites, after 15, 30, 45, and 60 minutes of cryogenic conditioning at 77K in a liquid nitrogen bath, the strength and modulus increase significantly with the increase of strain rate and reach the optimum value for 45 minutes of conditioning. The results are encouraging as they will be helpful in assessing the suitability of GFRP in the structural design of epoxy-based components for cryogenic applications.

• Composites Research
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• 제26권6호
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• pp.380-385
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• 2013

본 논문에서는 유리섬유복합재(glass fiber reinforced plastic composites)의 드릴가공조건변화에 따른 박리지수와 표면조도 특성이 분석되었다. 드릴 가공된 홀의 입출구에서 이미지 픽셀을 이용하여 박리지수를 산출할 수 있는 관계식이 유도되었으며, 복합재 시편을 제작하여 진동 및 열 영향을 최소화할 수 있는 가공조건에서 드릴가공을 수행하여 보다 신뢰성 있게 표면조도값을 얻기 위하여 6점평균표면조도측정 방식이 적용되었다. 실험 결과로부터 GFRP 드릴가공에서 박리지수는 이송속도 증가에 감소하고, 절삭속도 증가에도 미세하게 감소함을 볼 수 있었다. 또한 드릴가공된 홀 내부에서 표면조도는 이송속도가 증가할수록 증가하고, 절삭속도 변화에는 영향을 받지 않음이 파악되었다.

• 한국해양공학회지
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• 제16권4호
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• pp.48-53
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• 2002

Fiber-reinforced composites are extensively used in electronic, ship and aerospace applications due to their high strength and high toughess. In these applications, they are often subjected to localized heat damage due to various sources. In order to ensure their reliability, it is important to predict their residual properties using nondestructive evaluation thchniques. Fabric fiber composite specimens were manufactured with six layers of the glass-fiber prepreg and the carbon-fiber prepreg, respectively. The specimens were subjected to a localized heat damage using a heated copper tip with a diameter of 10mm at 35$0^{\circ}C$(CFRP) and 30$0^{\circ}C$(GFRP), respectively. The specimens were then subjected to tension tests while acoustic emission (AE) activities of specimens were collected. The AE activity of all specimens showed three types of distinct frequency regions. Those are matrix cracking, failure of the fiber/matrix interface and fiber breakage.

• 한국진공학회지
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• 제9권3호
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• pp.279-284
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• 2000

본 연구는 옥외용 epoxy/glass fiber의 열화과정을 분석하기 위하여 FRP 적층판을 고온과 수에 노출시켰다. 열화과정은 접촉각, 표면전위감쇠, 표면저항률의 비교에 의해 평가하였다. 젖음성의 변화는 열처리 시료에서 $200^{\circ}C$까지 접촉각이 증가하였지만 수분처리 시료는 감소하였다. 표면전위감쇠 특성은 수분처리 시료에서는 감소하지만, 열처리 시료는 미 처리와 비교해서 증가하였다. 또한, 표면저항률은 접촉각의 변화와 같은 경향을 보이고 있다.

• Composites Research
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• 제23권1호
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• pp.44-50
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• 2010

본 연구에서는 염수 침수 실험과 염수 분무 실험이라는 두 가지의 실험을 위그선의 구조재료로 사용될 3가지 다른 복합재료 시스템에 대해서 해수와의 접촉에 의한 물성저하를재현하기 위해 수행하였다. 140일간 염수환경하에서 노화시킨 후 탄소섬유 복합재료와유리섬유 복합재료의 인장, 압축, 전단 강성과 강도 및 층간 전단 강도를 측정하였다. 기본 물성파의 비교를 통해서 염수환경이 복합재료의 기계적 물성에 미치는 영향이 평가되었다. 실험을 통해 염수 분무환경과 침수 환경의 차이는 거의 영향을 미치지 않음을 확인하였다. 탄소섬유 복합재료의 경우 인장 물성에 적은 손실이 발생한 반면 유리섬유 복합재료에서는 인장물성의 저하률이 탄소섬유 복합재료에 비해서 큼을 확인하였다. 그리고 모재 지배적 물성들의 큰 물성저하가 관찰되었다. 이를 통해, 염수는 복합재료의 섬유와 모재 사이의 계면을 퇴화시키고, 또한 모재 자체 물성과 유리섬유의 물성을 저하시킬 수 있음을 확인하였다.