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고온다습한 환경이 CFRP 복합재료의 정적강도 거동 특성에 미치는 영향
홍석우(Suk Woo Hong),강민성(Min Sung Kang),안상수(Sang Soo Ahn),구재민(Jae Mean Koo),석창성(Chang Sung Seok) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.10
Recently, the use of Carbon Fiber Reinforced Plastic(CFRP) composite have been increased instead of metal material in the field which highly demands both lightweight and high specific strength materials such as aircraft and automobile. In the aircraft operating condition, the fuselage of aircraft is often exposed to severe condition between high temperatures and high humidity. Therefore, the estimation of strength properties of CFRP under real condition is highly necessary for the aircraft safety. In this study, CFRP specimens were made according to ASTM D3039, and tensile tests was performed at 75℃ and high humidity condition. After the tensile tests, fractured surfaces were analyzed to estimate the characteristics the CFRP composite in high temperature and humidity conditions using SEM.
고온 다습한 환경에 장기간 노출된 CFRP 복합재료의 특성 분석
홍석우(Suk-Woo Hong),안상수(Sang-Soo Ahn),구재민(Jae-Mean Koo),석창성(Chang-Sung Seok) 대한기계학회 2012 大韓機械學會論文集A Vol.36 No.8
탄소섬유강화(CFRP) 복합재료는 높은 비강성과 비강도 특성을 갖고 있기 때문에 항공기, 자동차 등의 경량화가 요구되는 분야에서 금속재를 대체하여 사용 빈도가 급격히 증가하고 있다. 그 중 항공기의 경우, 동체가 고온 다습한 환경 조건에 노출되는 경우가 많기 때문에 CFRP를 이용한 항공기의 건전성 확보를 위하여 실제 환경에서의 강도 특성을 연구할 필요가 있다. 본 논문에서는 CFRP시험편을 75℃의 물에 장기간 침지하였으며. 이 시험편을 이용해 침지 기간별로 인장강도를 평가하였다. 또한, SEM을 이용하여 흡습 기간에 따른 파단면의 파괴양상을 분석하였으며 300일간 침지된 시험편에 대해 응력비 R=0.1 조건으로 피로시험을 수행하여, 침지하지 않은 시험편에 비해 피로수명이 크게 저하되는 것을 확인하였다. Carbon fiber reinforced plastic (CFRP) composites have high specific stiffness and high specific strength. Therefore, they are increasingly being use, instead of conventional metallic materials in the aviation and automobile industries, where there is a strong demand for lightweight materials. In aircraft, the fuselage is exposed to severe conditions of high temperatures and high humidity. Therefore, it is necessary to estimate the strength of CFRP composites under real conditions from the viewpoint of aircraft safety. In this study, CFRP specimens were immersed in distilled water at 75℃ for a long time. Then, tensile tests were performed on these specimens, and the fracture characteristics of the fractured surfaces were analyzed using SEM. A fatigue test was performed on specimens immersed for 300 days with R=0.1, and it was confirmed that the fatigue life deteriorated in immersed specimens compared to specimens that were not immersed.
난포호르몬과 황체호르몬이 인간 자궁동맥의 내피비의존성 혈관 긴장도에 미치는 영향
홍석우(Suk Woo Hong),박형무(Byung Moo Park),허민(Min Hur),이무열(Moo Yeol Lee) 대한산부인과학회 2000 Obstetrics & Gynecology Science Vol.43 No.11
Objectives : The present study was performed to investigate whether estrogen and progesterone induce the change of vascular tone in endotheliumdenuded human uterine artery and vascular reactivity may be mediated by intracelluar calcium modulation through receptorand voltagedependent calcium channels. Methods : The uterine arteries were obtained at the time of hysterectomy from 28 women followed by denudation of endothelium. After confirmation of functional integrity of endothelium-denuded uterine artery, vascular reactivity was measured by using isometric force transducer and recorded by physiograph. Contraction was induced by 10-6 M norepinephrine and 35mM high concentrated potassium chloride solution which activated receptor-dependent calcium channel and voltage-dependent calcium channel, respectively.Thereafter estradiol of 4 different concentrations from 3×10-11M to 3×10-8M was administered. Progesterone was also administered to endothelium-denuded uterine artery which was contracted by 10-6M norepinephrine and high potassium chloride solution. To evaluate the effect of additional progesterone on vascular smooth muscle relaxation effect of estrogen,4 different progesterones in concentrations from 3×10-8M to 3×10-5M were given to vascular smooth muscle which was initially pretreated with norepinephrine followed by relaxation of estradiol. Results : Estradiols from 3×10-11M to 3×10-8M showed in significant dose-dependent vascular relaxation. Progesterones result in significant decrease in vascular contraction in concentration dependent manner. Additional progesterone on estrogenic effects also results in significant decrease in vascular contraction. Conclusion : Estradiol may have endothelium independent vasorelaxation effect in human uterine artery. These vasorelaxant effects may be mediated through antagonistic action for receptor-and voltage-dependent calcium channels in vascular smooth muscle. Progesterone also bring about vasorelaxation by same action in endothelium-denuded vascular smooth muscle. On estrogen induced vascular relaxation, progesterone results in additional vasorelaxation.