• Journal of Adhesion and Interface
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• v.8 no.4
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• pp.14-22
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• 2007

In the present study, the effect of milled glass powder and liquid-type nitrile rubber (NBR) on the thermal stability of phenolic resin and the dynamic mechanical properties of glass braid/phenolic composites has been investigated by means of thermogravimetric analysis and dynamical mechanical analysis. It was found that both milled glass power and NBR filled in the waterborne phenolic resin significantly influenced the thermal stability of phenolic resins and the storage modulus and tan delta of the composites. The presence of glass powder increased the thermal stability of the phenolic resin, whereas the presence of NBR resulted in the weight loss in the specific temperature range. The thermal stability of the phenolic resins without and with the fillers was dependent not only on the cure temperature but also on the cure time. The variation of the storage modulus and tan ${\delta}$ of strip-type glass braid/phenolic composites was also influenced with the introduction of glass powder and NBR to the phenolic matrix as well as by the cure conditions given.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.7
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• pp.347-352
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• 2019

This study focused on improving the cast quality of small-sized induction motor rotors during the die casting process. A new rotor core cast model was proposed based on previous research results and parametric studies. Numerical analyses using 3-dimensional half models were performed to evaluate the filling patterns of aluminum molten metals into a mold and on-site experiment performed to verify the newly proposed cast model. The following were obtained from numerical filling analyses and experimental results. First, molten metals started to fill the lower end ring, then moved on to fill the core slot and upper end ring and finally stopped to fill at the rotor core slot. Second, significant circulation of molten metals was not observed on the lower end ring, resulting in fewer defects at the section of the lower end ring from the experimental results. Third, the new shape of a rotor core cast was effective in producing rotors with sound cast quality, and reducing the end ring cast defect area by approximately 70 %.

• Journal of the Korea Society of Computer and Information
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• v.26 no.2
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• pp.53-60
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• 2021

In this paper, we aimed to identify the insulation characteristics and reliability of Epoxy composites, which are widely used as insulation material for electrical & electronic components and electric appliance. To this end, it was necessary to predict variations of electric field due to the distribution of fillers that must be added by economic and mechanical factors. So, we verified the result using an electric field analysis Simulator. Furthermore, under the condtion of DC voltage application, an dielectirc breakdown test was performed according to ambient temperature changes and the distribution of fillers, and the changes were observed. Three types of specimens were manufactured by adding 0, 50 and 100[phr] filling to Epoxy resin. In all specimens, as temperature was increased, the strength of the dielectric strength was decreased. When comparing the simulation results with the actual dielectric breakdown test results, we was able to confirm the technical applicability required for Insulation design of electric appliance.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.5
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• pp.143-149
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• 2020

The purpose of this study is to manufacture a variable density - hybrid lattice structure control by filling the pore of the metal addictive manufactured lattice structure with lightweight reactive acrylic compounds(RAC). To apply the variable density - hybrid lattice structure to the construction industry, the enhancing adhesion - reactive acrylic compounds(EA-RAC) which increased the adhesion strength was manufactured by adding ordinary portland cement to the RAC. Finally, the EA-RAC was filled into the lattice structure to test the specific density, water absorption, and adhesion strength of the variable density - hybrid lattice structure. The results were obtained with density controllable, water absorption less than 1.0%, and 1-day bonding strength of 1.78 MPa to 1.98 MPa.

• Composites Research
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• v.19 no.2
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• pp.7-12
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• 2006

Graphite particle/carbon fiber hybrid conductive polymer composites were fabricated by the compression molding technique. Graphite particles were mixed with an epoxy resin to impart the electrical conductivity in the composite materials. In this study, graphite reinforced conductive polymer composites with high filler loadings were manufactured to accomplish high electrical conductivity above 100S/cm. Graphite particles were the main filler to increase the electrical conductivity of composites by direct contact between graphite particles. While high filler loadings are needed to attain good electrical conductivity, the composites becomes brittle. So carbon fiber was added to compensate weakened mechanical property. With increasing the carbon fiber loading ratio, the electrical conductivity gradually decreased because non-conducting regions were generated in the carbon fiber cluster among carbon fibers, while the flexural strength increased. In the case of carbon fiber 20wt.% of the total system, the electrical conductivity decreased 27%, whereas the flexural strength increased 12%.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.3
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• pp.955-960
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• 2012

In this study, pure Polyurethane and commonly used flame retardants $Al(OH)_3$ and $Mg(OH)_2$, the add-in sample and Cloisite Na+, Cloisite 15A added sample of flammability and mechanical properties are compared. Sodium silicate and a mixture of polyurethane that the lightweight filler Vermiculite, Perlite addition of flame retardant and mechanical properties of the sample was confirmed. As a result, the flame retardant additive in the Vermiculite and Perlite in a flame-retardant grade sample except sample were identified. Tensile strength is degrade accord to the filler amount. But, Sodium silicate in the case of the sample add-in, other than confirmed that the sample strength increases.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2008.04a
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• pp.144-147
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• 2008

A glass bulb is the most reliable and simplest device for a fire sprinkler head system. We had developed an accurate glass bulb. The glass bulb is composed with a glass ampoule, liquid filled within the ampoule and an air bubble in the liquid. The first step of the development was to establish a stable mass production system for uniform glass ampoule. The second step is to optimize the composition of the liquid and the size of the bubble. It was also a difficult problem to devise manufacturing process to form uniform bubble size. The final step for the development is to control the mechanics for glass breaking by surface treatment for the glass bulb.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.4
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• pp.96-106
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• 2017

In pressable polymer bonded explosives (PBXs), densification occurs due to rearrangement and deformation of explosive particles during pressing. If brittle explosives are compressed till particle fraction become higher than theoretical random close packing fraction (RCPF), bigger particles should be fractured to fill the void. In this study, multi-modal particle system was introduced for the decrease in possibility of particle fracture during compression expecting decrease in shock sensitivity of highly filled pressable PBX. The experimental results showed the trimodal particle system had low sensitivity with high density, compared to bimodal particle system.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.321-321
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• 2013

열전재료는 열과 전기의 변환이 상호 가역적으로 일어나는 현상을 갖는 재료로서, 사용온도별로 여러 가지 재료가 개발되고 있다. 중온 영역에서 우수한 열전특성을 보이는 skutterudite는 격자 내에 2개의 공극을 갖고 있고 이에 적절한 원자를 충진하여 포논산란을 유도하고, PGEC(phonon-glass and electron-crystal) 개념을 적용하여 재료의 열적인 성질과 전기적인 성질을 동시에 제어함으로써 열전성능의 향상을 도모할 수 있는 재료이다. 본 연구에서는 챔버 내부 기체를 연속적으로 뽑아내어 진공도를 유지하는 방식이 아닌, 석영관을 앰플화한 진공밀폐 용해법을 사용하였다. 진공밀폐 용해법은 성분원소의 산화와 휘발을 억제하는데 있어 매우 유용한 공정이다. 용해를 통해 얻어진 잉곳을 용해와 동일한 방법으로 석영관에 밀봉하여 873 K에서 100시간 동안 진공열처리를 실시하였다. 또한, 합성된 잉곳의 기계적 특성 향상을 위해 $75{\mu}m$ 이하로 파쇄하여 진공 열간 압축 소결하였다. La가 충진된 $La_zCo_4Sb_{12}$ Skutterudites 단일상을 합성하여 La의 충진량(z)에 따른 열전특성과 전자이동특성을 조사하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.6
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• pp.1078-1085
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• 2006

In earthing technologies, the intrusion of the surge wave can be protected when the earthing resistance is as low as several ohms. However, the cost fer realizing such a low resistance is quite high. Therefore it is important to determine appropriate target value of the earthing resistance to install cost-effective grounding system. In this work, we have proposed an optimization method of the earthing resistance according to the various environmental parameters by using a numerical simulator We have also developed new catalyst composed of water-soluble alkaline elements and activated carbon and investigated its electrical characteristics for enhancement of the earthing qualities.