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Graphite/Epoxy 적층복합재의 층간파괴 향상을 위한 프리프레그의 전처리 연구
이경엽(Rhee K. Y.),김민호(Kim M. H.),백영남(Paik Y. N.),이위로(Lee W. R.) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
In this study, the graphite/epoxy prepregs were surface-treated using O² plasma, and optimal treatment time was determined measuring the contact angle. Interlaminar toughness of surface-treated graphite/epoxy composites was compared with that of regular (untreated) graphite/epoxy composites. The results showed that the contact angle was a minimum when treated for 30 minutes. The interlaminar toughness of surface-treated case was improved about 20% compared with that of regular case.
해저환경에서 탄소섬유/에폭시 복합재의 압축특성에 대한 변형률 효과
이경엽(K.Y. Rhee),이지훈(J.H. Lee),김현주(H. J. Kim) 한국해양환경·에너지학회 2004 한국해양환경공학회 학술대회논문집 Vol.2004 No.-
We investigated in this work the effect of strain rate on the compressive elastic modulus, compressive strength, and compressive strain of unidirectional carbon/epoxy composite in the deep-sea environment. Compressive tests were performed in the hydrostatic pressure environment of 270 MPa by applying three strain rates of 0.05 %/sec, 0.25 %/sec, and 0.55 %/sec. The results showed that the compressive strength is little affected by the strain rate while the compressive strain decreases with increasing strain rate. The results also showed that the elastic modulus increases as the strain rate increases.
극저온 볼 밀링을 통한 Ibuprofen 분말의 나노화Ⅱ
조현갑(H.K. Cho),이경엽(K.Y. Rhee),백영남(Y.N. Paik),박훈재(H.J. Park),이상목(S.M. Lee) 한국정밀공학회 2004 한국정밀공학회 학술발표대회 논문집 Vol.2004 No.10월
Reducing the particle size of drug materials down to submicron is an important matter in pharmaceutical industry. Cryogenic milling technology is one of the mechanical milling processes, which is mostly utilized in refining grain size of metal and ceramics at extremely low temperature environment. This technique has not been readily studied in application to medical and biotechnology. This paper, therefore, describes the application of cryogenic milling process to reduce particle size of Ibuprofen. The shape and size of the Ibuprofen particle before and after the cryogenic ball milling process were analyzed. XRD analysis was performed to examine a change in crystallinity of Ibuprofen by the cryogenic ball milling process. The results showed that the size of Ibuprofen particles was reduced to 1/10 or less of its initial size. The results also showed that the degree of crystallinity of Ibuprofen was slightly reduced after cryogenic ball milling with nitrogen.
Al-7.5%Mg 벌크소재의 정수압 압출특성에 관한 연구
윤창용(C. Y. Yoon),이경엽(K. Y. Rhee),이상목(S. M. Lee),박훈재(H. J. Park),김응주(E. J. Kim) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
This paper deals with the hydrostatic extrusion to make the nano-grained bulk material. Hot hydrostatic extrusion was performed using the hipped bulk Al-7.5%Mg. in order to investigate the effect of the hot hydrostatic extrusion on the nano-grained material. Tensile and compressional properties of the hipped and the extruded materials were compared to each other.