• 대한기계학회논문집A
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• 제31권3호
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• pp.295-303
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• 2007

Degradation behaviors of filament-winded composites have been evaluated under the accelerated environmental test of high temperature, water immersion and thermal impact conditions. Two kinds of laminated composites coated by an urethane resin have been used: carbon-fiber reinforced epoxy(T700/Epon-826, CFRP) and glass-fiber reinforced phenolic (E-glass/phenolic, GFRP). For tensile strength of $0^{\circ}$ composites, CFRP showed little degradation while GFRP did high reduction by 25% under the influence of high temperature and water However for water-immersed $90^{\circ}$ composites tensile strength of both CFRP and GFRP showed high reduction. Bending strength and modulus of $90^{\circ}$ composites were largely reduced in water-immersion as well as high temperature environment. Urethane coating on the composite surface improved the bending properties by 20%, however hardly showed such improvement for water-immersed $90^{\circ}$ composites. In case of shear strength and modulus, both CFRP and GFRP showed high reduction by water-Immersion test but did a slight increase by high temperature and thermal impact conditions.

• 한국재료학회지
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• 제27권4호
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• pp.199-205
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• 2017

In this study, (3,4-epoxycyclohexane)methyl 3,4-epoxycyclohexylcarboxylate acrylate was synthesized by reacting (3,4-epoxycyclohexane)methyl 3,4-epoxycyclohexylcarboxylate with acrylic acid to minimize hardening shrinkage and to improve heat resistance, which are known as disadvantages of photopolymers for 3D printing application. Urethane acrylate was synthesized by reacting 1,3,5-triazine-2,4,6-triamino alcohol, 2-hexylethyl acrylate, and isophorone diisocyanate in order to improve the mechanical properties without deteriorating the heat resistance. The physical properties before and after the synthesis of the acrylate and the mechanical properties when the urethane acrylate was applied were investigated. The reaction progress of the composite was examined by FTIR and $^{13}C$ NMR. The heat deflection temperature, flexural strength, and surface hardness of the molding were measured. The curing behavior by Photo-DSC ultraviolet irradiation was also examined.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2021년도 가을 학술논문 발표대회
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• pp.236-237
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• 2021

In the waterproofing of the rooftop of reinforced concrete buildings, it is difficult to solve perfectly according to the proficiency of waterproofing materials, methods, and mechanics. Therefore, this study applies a Tricot Fabric Mesh to the behavior of the bottom concrete. In addition, it responds to the behavior of the concrete cracking, and the waterproofing and protective layer has developed a method to provide convenience for rooftop floor use by adhesion between the base and the waterproof layer with the use of high viscosity urethane to effectively move the surface deformation and surface vapor and install a airvent device on the wall.

• Restorative Dentistry and Endodontics
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• 제12권1호
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• pp.7-24
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• 1986

The purpose of this study was to observe the compressive strength, compressive fatigue strength, surface hardness, water sorption and solubility of eight different posterior restorative composite resins. Eight composite resins were tested for their strength of the compressive and compressive fatigue with prepared two different types of specimens (I and T-type) using a Instron universal testing machine (model No. 1332). The hardness was measured with a Knoop hardness tester (MVH-2, Tokyo) for each cylindrical specimen, 7mm in diameter and 5mm thick. The water sorption and solubility were evaluated with the prepared composite resin disks, 20mm in diameter and 1mm thick. The results were as follows: 1. The compressive strength, compressive fatigue strength and hardness were noticed to be Increased by increasing the volume content of filler. 2. The compressive strength was appeared to be independent on the type of specimen, but the compressive fatigue strength was found to be greatly influenced by the type of specimens. 3. The composite resins having higher compressive strength had also higher compressive fatigue limits. 4. The compressive fatigue limits at $10^5$ stress cycles were about 50-80% of the compressive strength and were showen to be dependent on the materials and type of specimens. 5. The larger the filler particle size was, the lower was the water sorption. And the water sorption of BIS-GMA resin was higher than that of urethane resin. 6. The visible light-cured composite resin had a higher value of solubility than the chemically- cured composite resin. And the solubility tended to decrease by increasing the volume content of filler.

• 한국추진공학회지
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• 제8권1호
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• pp.70-80
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• 2004

본 연구에서는 한국과 같이 비교적 저 풍속인 지역에 적용 가능하도록 피치제어장치를 가진 1kW급 소형 풍력발전 시스템의 개발 결과를 제시하였다. 공력설계에서는 블레이드의 직경이 동급의 상용 블레이드 보다 과도하게 크지 않으면서도 저 풍속 지역에서 보다 효율적인 형상설계를 위해 여러 가지 설계 변수분석을 통한 파라미터 연구가 수행되었다. 또한 구조설계를 통해 풍력발전기에 작용하는 다양한 하중을 효과적으로 견딜 수 있는 경량의 복합재 구조가 설계되었다. 구조설계의 평가를 위해 유한요소 구조해석이 수행되었으며, 실물 구조시험을 수행하여 구조적 안전성을 확인하였다.

• 폴리머
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• 제36권4호
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• pp.413-419
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• 2012

폴리페닐렌에테르[PPE, poly(phenylene ether)] 수지의 경화성분으로서 다관능 우레탄 아크릴레이트 단량체를 합성하고, 이후 PPE와 혼합하여 유전체 기판을 제작하고 그 특성을 평가하였다. 단량체 합성 후 FTIR, NMR 분석을 통하여 우레탄 결합이 형성되었는지 확인하였다. 복합물 쉬트를 필름 코터로 성형한 후, 진공가 압적층하여 테스트 기판을 제작하고, 단량체의 종류 및 함량에 따른 유전율, 유전손실, peel 강도를 평가하였다. 2종의 하이드록시 아크릴레이트 중 페닐기를 가진 2-hydroxy-3-phenoxypropyl acrylate를 이용하여 합성된 단량체를 경화성분으로 사용한 경우 유전손실이 더 작았으며, 단량체의 함량이 줄어들면서 유전율과 손실이 감소하는 경향을 나타내었다. Peel 강도는 단량체의 종류에 따라서 특별한 경향성을 보이지 않았다. 실험결과 동박 접합 강도가 약 10 N이고, 1 GHz에서 유전율이 약 2.54, 유전손실이 0.0027로 작은 고주파 대역용 고분자 기판소재를 얻었다.

• 한국응용과학기술학회지
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• 제31권3호
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• pp.486-491
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• 2014

본 연구에서는, 유기용매를 사용하지 않는 친 환경적인 건식 공정과 초임계 공정을 이용한 Thin-multiwalled carbon nanotube (TWNTs)/아민계 에폭시 첨가제의 복합체 제조에 관하여 연구를 하였다. 제조된 TWNTs/아민계 에폭시 첨가제의 복합체는 우레탄기반의 비스페놀 A 타입의 에폭시 레진의 경화제로 사용하였다. TWNTs/아민계 에폭시 첨가제의 복합체를 경화제로 사용하여 제조된 에폭시 레진의 열적 성질을 Dynamic mechanical analysis (DMA)를 이용하여 분석 하였으며, 메트릭스상의 carbon nanotube의 높은 분산성은 SEM을 통하여 확인 하였다. 그 결과, 초임계 공정을 이용하여 제조된 에폭시 레진의 열적 성질과 매트릭스내의 carbon nanotube 분산성이 건식 공정을 사용 하였을 때 보다 더욱 증가된 결과를 확인 할 수 있었다.

• Current Photovoltaic Research
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• 제3권1호
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• pp.5-9
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• 2015

Absorption and luminescence characteristics of disperse red-19 (DR-19) and $TiO_2$ composite have been investigated with various poling electric field strengths. Two step synthetic processes were employed to employ the DR-19 to the $TiO_2$ sol-gel. Firstly, urethane bond formation between DR-19 (-OH) and 3-isocyanatopropyl triethoxysilane (ICPTES, -N=C=O) performed (ICPDR) prior incorporation to the $TiO_2$ sol-gel. Secondary, the hydrolysis of the ethoxy group from the ICPTES and condensation reaction between silanol groups from ICPTES and $TiO_2$ sol-gel were performed. The ICPDR and $TiO_2$ sol-gel ($DRTiO_2$) were mixed and stirred for several days. The composite was coated to the ITO coated glass substrate. Corona poling were performed before drying the composite with various electric field strengths. The absorption intensity decreased with the increase of the poling field strength, which resulted in the increase of poling efficiency. The photoluminescence also decreased as the poling field strength increased. There is long luminescence tail for the poled $DRTiO_2$ film compared with unpoled $DRTiO_2$ film. The luminescence long tail indicates that the self-trapped excitons and polarons were generated when the $DRTiO_2$ film was poled with electric field.

• 대한기계학회논문집A
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• 제28권12호
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• pp.1974-1981
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• 2004

This paper is concerned with the numerical investigation of the transfer characteristics of the landing impact force exerted on court sport shoes to the sport surface condition. The reaction force occurred by the impact between court sport shoes and sport surface is absorbed by shoes to some extent, but the remaining impact force is to transfer the human body from the sole of a foot. We consider four surface conditions, asphalt, urethane, clay and wood court surfaces. For the dynamic response analysis, we construct a coupled leg-shoes FEM model and create the multi-layered composite surface model. The numerical simulations are performed by an explicit nonlinear finite element method. Through the numerical experiments, we examine the transfer characteristics of the landing impact force to the surface condition.

• Composites Research
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• 제28권2호
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• pp.58-64
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• 2015

본 논문에서는 샌드위치 복합재 패널로 제작되는 사용후 핵연료 수송용기 충격완충체의 유효등가 유한 요소모델을 제시하는데 목적을 둔다. 샌드위치 복합재 패널은 금속재 면재와 각각 우레탄 폼, 발사목 그리고 레드우드 심재로 구성되었다. 충격완충체의 유효등가 유한요소 모델은 샌드위치 복합재 패널의 저속충격 시험과 해석결과와의 비교를 통해 제시되었으며, LS-DYNA 3D를 사용한 동적 외연 유한요소해석에 의해 수행되었다. 시험과 해석 결과, 충격완충체 샌드위치 패널의 유한요소 모델은 적층쉘 요소의 면재와 솔리드요소의 심재를 사용한 기존의 혼합모델링 기법에 비해 면재와 심재 모두 솔리드 요소를 적용하는 방법이 더 정확한 결과를 나타냄을 확인하였다. 이때 발사목과 레드우드 심재는 요소제거 기능을 갖는 솔리드 요소로 모델링 되는 것이 추천되어진다.