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CFRP/알루미늄 복합재에서 CFRP의 표면처리가 T-peel 강도에 미치는 영향
이경엽(Rhee Kyong Yop),양준호(Yang Jun Ho) 대한기계학회 2001 대한기계학회 춘추학술대회 Vol.2001 No.3
This study investigates the surface treatment of CFRP (Carbon Fiber Reinforced Composites) to improve the T-peel strength of CFRP/aluminum composites. The surface of CFRP ([0˚]₁₄) was treated by Ar? ion beam under oxygen environment. T-peel tests were performed based on the procedure of ASTM D1876-95. The results showed that the T-peel strength of surface-treated CFRP/aluminum composites was about 5.5 times greater than that of untreated CFRP/aluminum composites.
탄소섬유/에폭시 복합재로 보수된 알루미늄의 피로특성에 대한 연구
김만태(Man Tae Kim),이경엽(Kyong Yop Rhee) Korean Society for Precision Engineering 2004 한국정밀공학회지 Vol.21 No.11
For a present study, we investigated fatigue behavior of cracked aluminum repaired by unidirectional graphite/epoxy composite material. Three different specimens were used in the fatigue tests: cracked aluminum, cracked aluminum repaired by graphite/epoxy composite patch, and plasma-treated aluminum repaired by graphite/epoxy composite patch. The surface of the aluminum was treated using a DC plasma. The results showed that the fatigue crack growth behavior of cracked aluminum was significantly improved by repairing the cracked area with a composite patch. Specifically, the specimen repaired by composite patch showed about 300 % more fatigue life than the cracked aluminum. In particular, the plasma-treated aluminum repaired by composite patch showed almost 12 % more fatigue life than the cracked aluminum repaired by graphite/epoxy composite patch. The increased fatigue life of plasma-treated case was attributed to the surface roughness of aluminum by plasma treatment.
정수압 조건에서 변형률 변화가 섬유강화 복합재의 층간분리인성에 미치는 영향에 대한 연구
하성록(Sung Rok Ha),이경엽(Kyong Yop Rhee),김현주(Hyeon Ju Kim),정동호(Dong Ho Jung) Korean Society for Precision Engineering 2005 한국정밀공학회지 Vol.22 No.11
It is generally accepted that fracture toughness of fiber-reinforced polymer composites is affected by strain rate in an atmospheric pressure condition. For a present study, the strain rate effect on the fracture toughness of fiber-reinforced laminated composites in the hydrostatic pressure condition was investigated. For this purpose, fracture tests have been conducted using graphite/epoxy laminated composites applying three steps of the strain rate at 270 MPa hydrostatic pressure condition. The strain rates applied were 0.05 %/sec, 0.25 %/sec, and 0.55 %/sec. Fracture toughness was determined from the work factor approach as a function of applied strain rate. The result showed that fracture toughness decreased as the strain rate increased. Specifically, the fracture toughness decreased 12% as the strain rate increased from 0.05 %/sec to 0.55 %/sec.
극저온 볼 밀링을 통한 Ibuprofen 분말의 마이크로화
조현갑(Hyun Kab Cho),이경엽(Kyong Yop Rhee),백영남(Young Nam Paik),박훈재(Hoon Jae Park),이상목(Sang Mok Lee) Korean Society for Precision Engineering 2004 한국정밀공학회지 Vol.21 No.11
For the present study, the cryogenic ball milling process was applied to make Ibuprofen microsized. The cryogenic ball milling was performed at low temperature of about -180℃ for 6 hours. The particle size distribution was determined before and after the cryogenic process. X-ray diffraction (XRD) measurement was made to determine the effect of cryogenic process on the crystallinity of Ibuprofen. The results showed that the size of Ibuprofen was reduced about 10 times by the cryogenic process. The degree of crystallinity of Ibuprofen was slightly reduced by the cryogenic process.
정수압 압출을 이용한 Copper-clad Aluminum 복합재 제조에 대한 연구
한운용(Woon Yong Han),이경엽(Kyong Yop Rhee),박훈재(Hoon Jae Park),윤덕재(Duk Jae Yoon),김승수(Seung Soo Kim) Korean Society for Precision Engineering 2004 한국정밀공학회지 Vol.21 No.7
In this work, a copper-clad aluminum composite was fabricated using hot hydrostatic extrusion with various extrusion ratios (8.5, 19, 49) and semi-die angles (30, 45, 60 degree) at a temperature of 320℃. Material characteristics of copper-clad aluminum composites were determined from compression tests and hardness tests. The results showed that for ER of 8.5, the optimum semi-die angle was below or equal to 30 degree and a pressure drop was about 31 %. For ER of 19, the optimum semi-die angle was in the range of 40 to 50 degree and a pressure drop was about 38%. In the case of ER=49, the optimum semi-die angle was above or equal to 60 degree and a pressure drop was about 36%. Compressive yield strength was maximum for ER of 8.5 and semi-die angle of 30 degree and the value of maximum was 155 ㎫. Uniform hardness distribution was obtained as the extrusion ratio increases and the semi-die angle decreases. In the case of ER=8.5 and semi-die angle of 30 degree, the lowest extrusion pressure and the maximum comperssive yield strength was obtained. Therefor, it was concluded that the optimum extrusion condition for fabricated copper-clad aluminum composites under hydrostatic pressure environment was ER of 19 and semi-die angle of 30 degree.
금속재와 폴리에틸렌 재료간의 접착강도 향상에 대한 연구
이지훈(Ji hoon Lee),이경엽(Kyong Yop Rhee),김현주(Hyun Ju Kim),정동호(Dong Ho Jung) Korean Society for Precision Engineering 2007 한국정밀공학회지 Vol.24 No.12
Polyethylene is a typical hydrophobic material and it is difficult to bond the polyethylene material with metal material. Thus, it is important to modify the surface of polyethylene material to improve the bonding strength between the polyethylene and the metal materials. In this study, the surface modification of polyethylene material was investigated to improve the interfacial strength between the polyethylene and the steel materials. Polyethylene material was surface-modified in a plasma cleaner using an oxygen gas. Two cases of composites (surface-modified polyethylene/steel composite and regular (as-received) polyethylene/steel composite) were fabricated using a secondary bonding method. Shear and bending tests have been performed using the two cases of composites. The results showed that the contact angle did not change much as the modification time increased. However, the contact angle decreased from -76° to ~41° with the modification. The results also showed that the shear strength and the bending strength were improved about 3030 % and 7 %, respectively when the polyethylene was plasma-modified using an oxygen gas.