• Journal of the Korea Convergence Society
• /
• v.2 no.3
• /
• pp.1-6
• /
• 2011

Aluminum foam is one of the representative light-weight materials. In this study we analyzed the mechanical properties of the aluminum foam structures. Aluminum materials with pores have novel mechanical characteristics such as flame retardancy, damping, and energy absorption which are superior to those of polymer foam. Furthermore its reusable properties draw considerable interests. General properties, energy and acoustic absorption will be investigated and future research issues such as binding techniques of foam materials with other structures will be discussed through foam application examples.

• Proceedings of the KIEE Conference
• /
• 2008.07a
• /
• pp.436-437
• /
• 2008

초기투자비용의 과다 발생으로 제한적으로 시공되고 있는 지중송전케이블의 역사는 1971년 154kV급 OF케이블이 처음으로 한국전력에 의해 상용운전후 현재에 이르고 있으며, 최근들어 지중케이블에서 발생된 송전선로 고장은 대부분 대형화되고 있어 초창기 시공된 케이블 종류의 대부분을 차지하고 있는 OF 케이블의 현상태를 정확하게 진단하고 각종 현상들을 분석하여 결론을 도출하지 않으면 안된다. 실제 계통에서 운전되고 있는 설비를 철거하여 상태를 판정할 수 있는 여건이 아니기 때문에 케이블의 현상태를 정확하게 분석하기 위해서는 절연유의 분석 등 간접적인 방법을 택하지 않을 수 없다. OF 케이블에 있어서 급유조는 케이블의 성능에 가장 직접적인 영향을 미치는 구성요소이며, 급유조에서 기준치보다 $2{\sim}5$배에 해당되는 이상가스의 발생원인을 파악하여 예방대책을 수립할 수 있게 되었다. 분리기의 용접부분 또는 접합부분에 틈이 생기지 않도록 하고 틈 부위에는 세라믹이나 폴리머등으로 코팅하여 $H_2$가스의 과다 발생을 방지할 수 있었다.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2003.04a
• /
• pp.18-21
• /
• 2003

The effect of interface bonding strength on the recovery force of SMA wire reinforced polymer matrix composites was investigated by pullout test. Firstly, the recovery forces and transformation temperatures of various prestrained SMA wires were measured and 5% prestrained SMA wires were prepared for the reinforcements of composites. EPDM incorporated with 20vol% silicon carbide particles(SiCp) of 6, 12, $60{mutextrm{m}}$ size were used as matrix. Pullout test results showed that the interface bonding strength increased when the SiCp size decreased due to the increase of elastic modulus of matrix. Cyclic test of composites was performed through control of DC current at the constant displacement mode. The abrupt decrease of recovery force during cycle test at high current was occurred by thermal degradation of matrix. This was in good agreement with temperature related in the thermal degradation of matrix. The hysteresis of recovery force with respect to the temperature was compared between wire and composite and the hysterisis of composites was smaller than the wire due to less thermal conduction.

• Journal of Welding and Joining
• /
• v.28 no.3
• /
• pp.42-48
• /
• 2010

Polycarbonate (PC) and Acrylonitrile Butadiene Styrene (ABS) were welded by a combination of a diode laser and a CNC machining center. Laser beam delivered through the transparent PC and was absorbed in an opaque ABS. Polymers were melted and joined by absorbed and conducted heat. Experiments were carried out by varying working distance from 44mm to 50mm for the focus spot diameter control, laser input power from 10W to 25W, and scanning speed from 100 to 400mm/min. The weld bead and cross-section were analyzed for weld quality, and tensile results were presented through the joint force measurement. With focus distance at 48mm, laser power with 20W, and welding speed at 300mm/min, experimental results showed the best welding quality which bead size was measured to be 3.75mm. The shear strength at the given condition was $22.8N/mm^2$. Considering tensile strength of ABS is $43N/mm^2$, shear strength was sufficient to hold two materials. A single process was possible in a CNC machining system, surface processing, hole machining and welding. As a result, the process cycle time was reduced to 25%. Compared to a typical process, specimens were fabricated in a single process, with high precision.

• Polymer(Korea)
• /
• v.31 no.4
• /
• pp.308-314
• /
• 2007

A composite film of polyurethane(PU)-graft-poly(acrylic acid) (PAAc)/polyaniline (PU-g-AAc/PANI) was successfully fabricated for the purpose of adding conductivity on the surface of a general purpose polymer and improving adhesive property between the general purpose polymer and conducting polymer layer. The results from ATR-FTIR and XPS analyses also supported the successful synthesis of the composite film by showing characteristic peaks for every step. A low surface resistivity of $2{\times}10^3\;ohm/sq$ proved the surface conductivity of synthesized PU-g-AAc/PANI film and the surface resistance decreased with increasing the amount of grafted AAc, which acted as a dopant for PANI film.

• Journal of Biomedical Engineering Research
• /
• v.25 no.1
• /
• pp.1-4
• /
• 2004

On the background of general idea and technique of bioscience, medicine and engineering, tissue engineering aim at maintenance, improvement and repair of human body function through manufacturing and transplantation of artificial tissue and organ exchangeable human body. Basic material used in the area is scaffold that aid tissue and organ formation. Making scaffold, solvent-casting and particulate leaching technique is widely used in manufacturing of porous polymer scaffold. There are many types of particle including salt and gelatin. Salt is a most commonly used particulate because it is easily available and very easy to handle and gelatin particle is another candidate for this method because it is known as a material, which enhances cell attachment and proliferation. But there is no comparative study of two kinds of materials. In this study we compared the biocompatibility of the two scaffolds made from salt(salt scaffold) and gelatin particle (gelatin scaffold). These results demonstrated that gelatin scaffold showed better attachment of cells at the initial stage and better proliferation of cells. The better performance of gelatin scaffold is contributed to the better connection of pores in the same porosity.

• Korean Journal of Optics and Photonics
• /
• v.25 no.4
• /
• pp.221-224
• /
• 2014

We present a method for manufacturing a TIM used for packaging a high-power LED. In this method a mixture of diamond powder and hydrogen peroxide is used as a filler epoxy. The thermal resistance of the TIM with hydrogen peroxide was improved by about 30% over the thermal resistance of the TIM without hydrogen peroxide. We demonstrate that as a result the heat generated from the chip is easily dissipated through the TIM.

• Polymer(Korea)
• /
• v.36 no.4
• /
• pp.434-439
• /
• 2012

To improve the performance of ionic polymer-metal composite (IPMC) actuators, Nafion films sandwiched with Nafion/conducting nanoparticulate electrospun webs were used as polymer electrolytes of IPMC. Multiwalled carbon nanotube (MWNT) and silver were the conducting nanoparticulates and the nanoparticles dispersed in a Nafion solution were electrospun. IPMCs with the Nafion/conducting nanoparticulate electrospun webs displayed improved displacements, response rates, and blocking forces. MWNT was superior to silver in terms of displacement and blocking force, and the webs without the conducting fillers also caused enhanced performances compared with the conventional IPMCs. These improvements were attributed to an elevated electrolyte flux through highly porous interlayers and capacitance induced by well dispersed conducting fillers, and low interfacial resistance between electrolyte and electrodes.

• Polymer(Korea)
• /
• v.27 no.4
• /
• pp.340-348
• /
• 2003

A previous stud-pull test was modified to measure the bond strength of polyurethane foam to carbon steel substrate. This test was appropriate in that the specimen foamed on Zn phosphated steel (0.95 kN) was broken at higher load than that of smooth galvanizing treated steel (0.38 kN). Among the samples foamed on the substrate atvarious preheating temperatures, the polyurethane foam to the steel held over 60$^{\circ}C$ exhibited very high bond strength. The samples were exposed at water vapor absorption, and, then, their bond strengths were measured. The adhesion was significantly reduced in the samples foamed on the steel at temperatures below 40$^{\circ}C$ and above 70$^{\circ}C$. For the polyurethane foams formulated with two blowing gases, the adhesion was higher by 0.03 kN in the samples with HCFC-l4lb than that with HFC-245fa. When the these samples were exposed at water vapor soaking, the reduction of the bond strength for the HFC-245fa blown sample was negligible due to smaller area fraction of void area filled with gas at interfacial area. Consequently, it was found that adhesion of polyurethane foam to metal substrate was determined by variation of microstructural features with substrate preheating, surface treatment type of blowing agent.

• Polymer(Korea)
• /
• v.34 no.3
• /
• pp.191-197
• /
• 2010

To improve the curing method of anisotropic conductive film (ACF) at low temperature, it was studied to replace the thermal latent curing agent of imidazole compounds by the curing agent of cationically initiating type. Thermo-mechanical properties such as glass transition temperature, storage modulus, and coefficient of thermal expansion were investigated for the analysis of curing behavior. The reliability of ACF were observed in thermal cycle and high temperature-high humidity test. ACF using cationic initiator showed faster curing, lower CTE, and higher $T_g$ than the case of using imidazole curing agent, which is important for the high temperature stability. Furthermore, ACF using cationic initiator maintained a stable contact resistance in reliability test, although it was cured at low temperature and fast rate. With these results, it was confirmed that the curing method of epoxy had great effect on thermo-mechanical properties and reliability of ACF.