• Steel and Composite Structures
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• 제19권6호
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• pp.1531-1548
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• 2015

The aim of this study is to investigate the relationship between Barcol hardness (H) and flexural modulus (E) degradation of composite sheets subjected to flexural fatigue. The resin transfer molding (RTM) method was used to produce 3-mm-thick composite sheets with fiber volume fraction of 44%. The composite sheets were subjected to flexural fatigue tests and Barcol scale hardness measurements. After these tests, the stiffness and hardness degradations were investigated in the composite sheets that failed after around one million cycles (stage III). Flexural modulus degradation values were in the range of 0.41-0.42 with the corresponding measured hardness degradation values in the range of 0.25-0.32 for the all fatigued composite sheets. Thus, a 25% reduction in the initial hardness and a 41% reduction in the initial flexural modulus can be taken as the failure criteria. The results showed that a reasonably well-defined relationship between Barcol hardness and flexural modulus degradation in the distance range.

• Advances in nano research
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• 제13권1호
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• pp.97-111
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• 2022

In the present article, silica nanoparticles (SNPs) were exploited to improve the tribological and mechanical properties of vinyl ester/glass fiber composites. To the best of our knowledge, there hasn't been any prior study on the wear properties of glass fiber reinforced vinyl ester SiO₂ nanocomposites. The wear resistance is a critical concern in many industries which needs to be managed effectively to reduce high costs. To examine the influence of SNPs on the mechanical properties, seven different weight percentages of vinyl ester/nano-silica composites were initially fabricated. Afterward, based on the tensile testing results of the silica nanocomposites, four wt% of SNPs were selected to fabricate a ternary composite composed of vinyl ester/glass fiber/nano-silica using vacuum-assisted resin transfer molding. At the next stage, the tensile, three-point flexural, Charpy impact, and pin-on-disk wear tests were performed on the ternary composites. The fractured surfaces were analyzed by scanning electron microscopy (SEM) images after conducting previous tests. The most important and interesting result of this study was the development of a nanocomposite that exhibited a 52.2% decrease in the mean coefficient of friction (COF) by augmenting the SNPs, which is beneficial for the fabrication/repair of composite/steel energy pipelines as well as hydraulic and pneumatic pipe systems conveying abrasive materials. Moreover, the weight loss due to wearing the ternary composite containing one wt% of SNPs was significantly reduced by 70%. Such enhanced property of the fabricated nanocomposite may also be an important design factor for marine structures, bridges, and transportation of wind turbine blades.

• 한국산학기술학회논문지
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• 제20권12호
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• pp.27-36
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• 2019

작은 굴절률 및 높은 굴절률을 갖는 저 분산 렌즈에 대한 요구가 증가함에 따라, 높은 내열성 및 내마모성을 갖는 이형성 보호 필름에 대한 필요성이 증가하고 있다. 그러나 광학 산업은 비구면 유리 렌즈 성형에 사용되는 이형보호 필름의 제조 공정 및 품질 표준에 대한 명확한 표준을 아직 확립하지 못했다. 이 기술은 광학 렌즈를 제조하는 각 회사의 노하우로 취급된다. 본 연구에서는 FCVA (Filtered Cathode Vacuum Arc) 기반 ta-C 박막 코팅의 이온에칭, 각 소스 및 필터부의 마그네트론 및 아크 전류, 바이어스 전압의 최적화에 관한 실험을 수행하였다. 그 결과, 코팅성능 측면에서, 이리듐- 레늄 합금 박막 스퍼터링 제품 대비 필름 두께가 약 50% 얇고, 경도는 약 20%, 박막의 접착강도는 약 40 % 개선된 것으로 측정되었다. 본 연구의 박막 코팅 공정 결과는 금형 이형 박막층의 최소 기계적 특성 및 품질 확립을 위한 유리 렌즈의 개발 및 활용에 크게 기여할 것으로 사료된다.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2000년도 춘계학술대회 논문집
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• pp.157-163
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• 2000

The application as the parts of an automobile, using the property of GMT-Sheet, is increasing. In order to exchange the parts of an automobile for GMT-Sheet, at first, the establishment and joining problem of exact joining strength must be determined. We have studied it using composites which is not same each other fiber oriented condition so as to determine joining strength and joining condition of GMT-Sheet. In this study, the result of experiment of forming condition concerned joining problem of GMT-Sheet is this ; joining efficiency of GMT-Sheet, increases as lap joint length L increases. Increase of compression ration cause decrease of joining efficiency after of GMT-Sheet, joining. In the viewpoint of recycling, randomly oriented composite of GMT-Sheet is desirable more than unidirectional oriented composite. We have better design the structure so as not occur to stress centralization on the joining part.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.553-553
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• 2000

The application as the parts of an automobile, using the property of GMT-Sheet, is increasing. In order to exchange the parts of an automobile for GMT-Sheet, at first, the establishment and joining problem of exact joining strength must be determined. We have studied it using composites which is not same each other fiber oriented condition so as to determine joining strength and joining condition of GMT-Sheet. h this study, the result of experiment of forming condition concerned joining problem of GMT-Sheet is this ; joining efficiency of of GMT-Sheet, increases as lap joint length L increases. Increase of compression ratio causes decrease of joining efficiency after of GMT-Sheet joining. In the viewpoint of recycling, randomly oriented composite of GMT-Sheet is desirable more than unidirectional oriented composite. We has better design the structure so as not to occur to stress centralizatien on the joining part.

• 한국생산제조학회지
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• 제23권6호
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• pp.547-554
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• 2014

CVD SiC is a perfect material used for molds/dies in hot press molding of glass lens. In its fabrication process, nano-precision polishing is essential finally. For this purpose, a novel polishing method using MCF (Magnetic Compound Fluid) slurry is proposed. In this method, MCF slurry is supplied into a given gap between the workpiece and a MCF slurry carrier, and constrained within the polishing zone by magnetic forces from permanent magnet. In this paper, after an experimental rig used to actually realize the proposed method has been constructed, the fundamental polishing characteristics of CVD SiC such as the effects of process parameters including MCF slurry composition on work-surface roughness were experimentally investigated. As a result, nano-precision surface finish of CVD SiC was successfully attained with MCF slurry and the optimum process parameters for obtaining the smoothest work-surface were determined.

• Advances in nano research
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• 제15권1호
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• pp.49-57
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• 2023

As composite materials are used in many applications, the modern world looks forward to significant progress. An overview of the application of composite fiber materials in sports equipment is provided in this article, focusing primarily on the advantages of these materials when applied to sports equipment, as well as an Analysis of the influence of sports equipment of fiber-reinforced composite material on social sports development. The present study investigated surface morphology and physical and mechanical properties of S-glass fiber epoxy composites containing Al₂O₃ nanofillers (for example, 1 wt%, 2 wt%, 3 wt%, 4 wt%). A mechanical stirrer and ultrasonication combined the Al₂O₃ nanofiller with the matrix in varying amounts. A compression molding method was used to produce sheet composites. A first physical observation is well done, which confirms that nanoparticles are deposited on the fiber, and adhesive bonds are formed. Al₂O₃ nanofiller crystalline structure was investigated by X-ray diffraction, and its surface morphology was examined by scanning electron microscope (SEM). In the experimental test, nanofiller content was added at a rate of 1, 2, and 3% by weight, which caused a gradual decrease in void fraction by 2.851, 2.533, and 1.724%, respectively, an increase from 2.7%. The atomic bonding mechanism shows molecular bonding between nanoparticles and fibers. At temperatures between 60 ℃ and 380 ℃, Thermogravimetric Analysis (TGA) analysis shows that NPs deposition improves the thermal properties of the fibers and causes negligible weight reduction (percentage). Thermal stability of the composites was therefore presented up to 380 ℃. The Fourier Transform Infrared Spectrometer (FTIR) spectrum confirms that nanoparticles have been deposited successfully on the fiber.

• Composites Research
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• 제34권1호
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• pp.47-50
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• 2021

본 논문은 차량에 사용되는 B필러의 강화재를 기존의 스틸 소재에서 CFRP(Carbon Fiber Reinforced Plastics)와 GFRP(Glass Fiber Reinforced Plastics)로 대체하여 경량화하는 것이 목표다. 이를 위해서는 무게는 감소시키면서 기존 B필러를 대체할 수 있는 구조안정성을 확보해야 한다. 기존 B필러는 스틸 아우터(outer)를 포함하여 다양한 형상의 스틸 강화재로 구성되며, 이와 같은 스틸 강화재 중 2가지의 스틸 강화재를 복합재로 대체하고자 한다. 이와 같은 스틸 강화재는 강화재 각각을 따로 제작하여 용접을 통해 결합되지만, 복합재 강화재는 패치(patch) 형태의 CFRP와 리브(rib) 구조의 GFRP를 활용하여 압축과 사출 공정을 통해 한번에 제작된다. CFRP는 B필러의 고강도부에 부착되어 측면 하중에 저항하도록 하였으며, GFRP 리브는 위상 최적화(Topology optimization) 기법을 통해 비틀림과 측면 하중을 저항하도록 설계하였다. 구조해석을 통해 기존 스틸 강화재와 비교 분석을 수행하였고, 경량화율을 산출하였다.

• 대한기계학회논문집A
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• 제38권8호
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• pp.849-855
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• 2014

유리섬유강화 플라스틱 복합재료의 압축성형 시, 모재와 유리섬유의 분리 없이 유동성이 우수하고, 불균질한 섬유배향이 없는 GFRP 복합재료 개발에 관한 체계적인 연구결과는 미흡한 실정이다. GFRP 복합재료를 사용하여, 자동차 부품 성형 시 발생하는 불균질도와 섬유배향 발생을 억제하는 많은 연구를 해왔으나 아직 해결되고 있지 않다. 본 연구에서는 위의 문제점들을 해결하기 위해 섬유유동성이 뛰어나고, 섬유배향이 발생하지 않고, 불균질성이 없으며, 구조안정성, 함침도, 기계적 특성 및 재활용성 등이 우수한 유리섬유강화 플라스틱 프리프레그를 제조하여, 수직교차형 평직직조방법을 적용하여, GFRP(Glass Fiber Reinforced Plastic) Sheet 를 제조한다.

• 한국재료학회지
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• 제4권7호
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• pp.733-740
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• 1994

페놀수지 결합재에 보강섬유의 종류에 따라서 내염섬유 보강 복합재(OFRP), 탄소섬유 보강 복합재(CFRP), 유리섬유 보강 복합재(GFRP), 아라미드 섬유 보강 복합재(AFRP)를 제조하였다. 각 보강섬유의 분율을 달리함에 따라 마찰계수 및 마모율을 측정하여 각 보강섬유의 특성이 미치는 영향을 관찰하였다. 아라미드의 섬유량이 45tw%일 때 평균 마찰계수가 0.353-0.383으로 가장 높게 나타난 반면에 핏치계 탄소섬유를 45wt% 보강한 경우 0.164-0.190으로 가장 낮게 나타났다. AFRP와 CFRP의 마모율은 낮게 나타내었으며, GFRP와 OFRP는 섬유분율이 증가함에 따라 급격히 증가하는 양상을 보였다. OFRP는 마모 diagram이 불안정하였으며 CFRP와 AFRP는 대체적으로 안정한 형태를 나타내었다. GFRp는 상당히 불안정한 마모diagram을 나타낸 것으로 보아 마찰 안정성이 가장 떨어짐을 알 수 있었다.