• 대한기계학회논문집A
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• 제29권6호
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• pp.876-888
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• 2005

Tensile properties and fracture toughness of monolithic aluminum, fiber reinforced plastics and glass fiber/aluminum hybrid laminates under tensile loads have been investigated using plain coupon and single-edge-notched specimens. Elastic modulus and ultimate tensile strength of GFMLs showed different characteristic behaviors according to the Al kind, fiber orientation and composition ratio. Fracture, toughness of A-GFML-UD which was determined by the evaluation of $K_{IC}$ and $G_{IC}$ based on critical load was similar to that of GFRP-UD and was much higher than monolithic Al. Therefore, A-GFML-UD presented superior fracture toughness as well as prominent damage tolerance in comparison to its constituent Al. By separating Al sheet from GFMLs after the test, optical microscope observation of fracture zone of GFRP layer in the vicinity of crack tip revealed that crack advance of GFMLs depended on the orientation of fiber layer as well as Al/fiber composition ratio.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2004년도 춘계학술발표대회 논문집
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• pp.119-122
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• 2004

A CPGFRP(Carbon Powder Glass Fiber Reinforced Plastics) sensor was fabricated for fine crack detection of structures. The electrical resistance of the sensor was measured on condition of various composition of carbon powders and thickness of bundle of glass fibers. The resistance was decreased as the increase of the content of carbon powders and the TEX of the glass fibers. In the case of loading on CPGFRP sensor, because inner crack was propagated, the part of percolation structures was disconnected. The sensor is superior to carbon fiber for the detecting ability of fine crack.

• 한국전산구조공학회논문집
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• 제32권6호
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• pp.349-357
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• 2019

유한요소법(finite element method)은 다양한 분야에서 재료의 역학적 거동을 더욱더 현실적으로 해석하고 예측하는 방법으로 다양한 분야의 제품 개발에 적용되고 있다. 하지만 섬유배향과 변형률 속도가 역학적 특성에 영향을 미치는 유리섬유 강화 플라스틱 복합재료에 관한 수치해석을 이용한 접근 방법은 현재까지 다소 어려움이 있다. 본 연구의 목적은 고분자, 고무, 금속 등과 같은 다양한 복합재료를 위한 선형, 비선형 다중스케일 재료 모델링 프로그램인 Digimat의 수치해석 재료 모델을 활용하여 유리섬유 강화 플라스틱 복합재료의 역학적 특성을 정의하고 검증하는 것에 있다. 또한 이를 통해 좀더 현실적으로 고분자 복합재료의 거동을 예측하고자 한다. 이를 위해 다양한 고분자 중 30wt%의 단섬유 질량 비율을 갖는 폴리부틸렌 텔레프탈레이트(polybutylene terephthalate, PBT)의 섬유배향과 변형률 속도에 따른 인장 특성을 참고문헌을 통해 조사하였다. 또한 Moldflow 프로그램을 사용한 사출해석을 통해 유리섬유 배향 정보를 계산하였으며 이를 매핑(mapping) 과정을 통해 유한요소 인장 시편 모델에 전달하였다. 대표적인 유한요소 상용 프로그램 중 하나인 LS-DYNA는 유리섬유 배향과 변형률 속도에 따른 복합재료의 인장 특성을 연구하기 위해 Digimat과의 연성해석(coupled analysis)에 활용되었다. 그리고 유리섬유 강화 플라스틱 복합재료를 해석하기 위한 LS-DYNA의 다양한 비등방성(anisotropic) 재료 모델들의 장단점을 서로 비교하고 평가하였다.

• 한국건축시공학회지
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• 제23권5호
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• pp.509-517
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• 2023

철근 부식을 해결하기 위해 FRP에 관한 연구가 증가하고 있다. CFRP는 경량화로 시공성이 용이하며, 내식성 및 내화학성이 뛰어나 이형철근 대체제로 지목되고 있다. 하지만 CFRP는 섬유와 레진을 압착하여 만들어져 열에 취약한 단점이 존재한다. 이러한 CFRP에 관한 연구는 미비한 실정이며, 본 연구에서는 고온 가열 이후 CFRP와 GFRP의 부착강도에 관한 연구를 실시하였다. 그 결과 규사코팅 CFRP와 리브형 CFRP, GFRP 모두 비슷한 부착강도 발현을 보였다.

• Structural Engineering and Mechanics
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• 제63권5호
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• pp.575-583
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• 2017

The study covers the behavior of reinforced concrete deep beams loaded under 4-point bending, failed by shear and repaired using bonding glass fiber reinforced plastics fabrics (GFRP) patches. Two rehabilitation methods have been used to highlight the influence of the composite on the ultimate strength of the beams and their failure modes. In the first series of trials the work has been focused on the reinforcement/rehabilitation of the beam by following the continuous configuration of the FRP fabric. The patch with a U-shape did not provide satisfactory results because this reinforcement strategy does not allow to increase the ultimate strength or to avoid the abrupt shear failure mode. A second methodology of rehabilitation/reinforcement has been developed in the form of SCR (Strips of Critical Region), in which the composite materials reinforcements are positioned to band the inclined cracks (shear) caused by the shear force. The results obtained by using this method lead a superior out come in terms of ultimate strength and change of the failure mode from abrupt shearing to ductile bending.

• 대한기계학회논문집A
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• 제37권2호
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• pp.199-204
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• 2013

최근 차량 경량화를 통한 에너지 절감을 위해서 무거운 철강재료를 경금속이나 복합재료로 대체하는 연구가 많이 진행되고 있다. 이중, 폴리머 기반의 복합재료는 사출성형을 통해서 복잡한 형상의 제작이 가능하고, 유리섬유나 탄소섬유를 함께 사용하여 철강재료 수준으로 기계적 물성을 높일 수 있는 장점이 있다. 하지만 엔진의 고온과 우기에서의 높은 습도 환경은 폴리머의 기계적 물성을 낮추기 때문에 재료선택 과정에서 반드시 고려해야 한다. 본 연구에서는 사출성형을 통해 만들어진 유리섬유강화플라스틱을 엔진룸 내부 온도와 유사한 $85^{\circ}C$ 환경과 우기시의 최대 수분흡수 환경하에서의 기계적 물성변화를 인장시험을 통해 알아보았다. 그 결과, 고온환경에서 최대인장강도가 약 23% 감소를 보였고, 수분에 의해서는 약 30% 감소하였으며, 고온과 수분 모두에 대해서는 약 70% 감소를 확인하였으며 이는 재료 선정시 반드시 고려해야 할 영향으로 판단되었다.

• 한국전기전자재료학회논문지
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• 제11권3호
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• pp.174-180
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• 1998

In this work, the properties of FRP, which is applied recently in the composite insulating materials, by thermal treatment were investigated. The specimens were epoxy glass laminates fabricated by thermal press method and had the volume content of 46[%] cutted $45^{\circ}C$ in the fiber direction and 1.0[mm] thickness. The experimental results showed that the amount of weight loss, wettability, surface potential, and surface resistivity increased up to 200[$^{\circ}C$] as a function of temperature. Usually, most degradations caused the hydrophilic to decrease the contact angle. But, in this work on thermal-degradated FRP, we can confirm the introduction of hydrophobic properties by cross-linking and the ablation of polar small-molecules rather than chain scission and oxidation. Finally, weight loss and contact angle increased. These phenomena show the existence of hydrophobic surface. With the change to the hydrophobic surface and the electrical potential and resistivity on FRP surface increased. But, the dielectric properties and tensile stength are decreased.

• 비파괴검사학회지
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• 제10권2호
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• pp.50-55
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• 1990

Flaws in GFRP(Glass Fiber Reinforced Plastics) were thermally detected using cholesteric liquid crystals. Presence of flaws changes the thermal conductivity of GFRP, and disturbs heat flow. When a uniform heat source is applied, the surface temperature of flawed region is different from that of sound region. The surface temperature distributions were measured by thermo-optic properties of liquid crystal. Since the colors of liquid crystal indicate temperature distribution of GFRP surface, the thermal disturbance by flaws could be detected. The locations of flaws in GFRP could be determined from the distribution of liquid crystal colors.

• 한국안전학회지
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• 제12권2호
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• pp.65-69
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• 1997

Especially, Fiber glass Reinforced Plastics(FRP) is the best composite insulating material which has been so far. Therefore, it's worthy of notice to investigate on the corona electrified composite insulating material by surface condition. And then some other materials will be focussed on. In this study, charge decay were measured with charging-time and grid voltage on FRP composite material surface in order to analyze the mechanism. As a result we have studied that the way of the composite glass fiber(GF) and Polymer and the condition of the contaminated surface was different. In case of the GF is mixed with vertical, charge decay speed is fast because the charge is easily leaked. On the other hand, the surface charge decay speed is depend on conductive or insulated of the contaminant.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1989년도 하계종합학술대회 논문집
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• pp.353-355
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• 1989

Composite insulating materials have the defect of interface. To minimize the defect of interface of GFRP (glass cloth reinforced plastics), coupling agent is treated. In this paper, the method of coupling agent treatment has been studied. The result shows that the optimum electric and mechanical properties is obtained for the sample treated on the glass fiber with 0.3% amino silane water solution.