• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.10a
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• pp.237-240
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• 2002

Amino terminated polyetherimide(ATPEI) has been synthesized by bisphthalic anhydride arid m-phenylenediamine, after that characterized by differential scanning calorimetry(DSC), thermogravimetric analyzer(TGA). Fourier transform (FT-IR) spectroscopy and gel permeation chromatography(GPC). ATPEI was blend to improve the toughness of bisphenol-A type epoxy resin which was cured by nadic methyl anhydride(NMA). The fracture toughness and the molphology of the toughened epoxy resin was evaluated. The toughness of ATPEI modified epoxy resin was higher than that of the PEI modified epoxy resin. In addtion, carbon fiber/ATPEI modified epoxy resin composites were fabricated and the mechanical properties of the resulted composites were investigated.

• Polymer(Korea)
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• v.38 no.2
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• pp.171-179
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• 2014

Low temperature cure prepregs are being developed for use in the preparation of large-structured fiber-reinforced polymer (FRP) composites with good performance. Cure behavior and chemorheology of low temperature cure epoxy resin system, based on epoxy resin, curing agent, and accelerators, were investigated to provide a matrix resin suitable for the prepreg preparation. Characteristics of cure reaction were studied in both dynamic and isothermal conditions by means of differential scanning calorimetry and rheometry. The low temperature cure epoxy resin system suggested in this study as a matrix resin was curable at $80^{\circ}C$ for 3 h, and showed the gel times of 120 and 20 min at 80 and $90^{\circ}C$, respectively. Thermal and mechanical properties of the cured sample were almost the same as high temperature cure counterparts.

• Composites Research
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• v.12 no.2
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• pp.70-81
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• 1999

Resin transfer molding(RTM) as a composite manufacturing process is currently of great interest in the aerospace industry requiring high performance composite parts. In this study, an analysis of mold filling in the RTM process was carried out by numerical simulation using finite element/control volume technique. Experimental work for the visualization of resin flow through fibrous preform was also conducted in order to quantitatively measure the permeabilities of the fiber mats and to evaluate the validity of the developed numerical code. The different types of fiber mats and silicon oils were selected as reinforcements and resin materials, respectively. The effects of fibrous preform structure, mold geometry, and preplaced insert on the flow front patterns during mold filling were examined by integrating the model predictions and experimental results. The flow fronts predicted by numerical simulation were in good agreement with those observed experimentally. However, according to the regions of the mold, some deviations between predicted and observed flow fronts could be found because of non-uniform fiber volume fraction. Weldline locations for the resin flow through round insert preplaced in the mold could be qualitatively deduced based on predicted flow fronts.

• Proceedings of the Korean Fiber Society Conference
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• 2003.04a
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• pp.352-353
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• 2003

Clay 분산 유/무기 나노복합재 제조기술은 실리케이트 층상구조의 점토광물을 나노 스케일의 시트상의 기본 단위로 박리(exfoliation)하여 고분자수지에 분산시킴으로써 범용 고분자의 낮은 기계적 물성의 한계를 엔지니어링 플라스틱 수준으로까지 올리고자 하는 것으로서, 기존의 무기 충진재 및 강화재의 입자크기(〉1 $\mu\textrm{m}$)를 나노 스케일까지 분산시켜 기존 무기물 충진 복합재의 단점을 한층 보완하는 것을 목표로 하고 있어 성능 및 원가 면에서 매우 유리한 방법으로 21세기의 복합재료 생산시장의 판도에 상당한 변화를 가져오게 할 수 있는 핵심기술이라 할 수 있다. (중략)

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.222-223
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• 2006

고전압 전기기기의 열화는 여러 가지 요인에 의해 발생한다. 따라서 여러 환경 요인에 영향을 비교적 적게 맡는 절연재료 개발에 의한 절연성능 항상은 그동안 많은 연구자들의 관심의 대상이 되어왔다. 최근 고분자 수지 내에 나노 크기의 충진제를 혼합하여 절연성능 및 기계적, 열적 특성을 향상시키는 연구가 점차 활성화되고 있다. 그러나 나노 크기 입자의 활용은 분자단위 크기의 입자가 가지는 Van der Waals력의 문제로 인하여 전기기기의 절연재료로 활용하기에는 어려운 점이 나타나고 있다. 본 논문에서는 에폭시/$SiO_2$ 나노복합재료를 제조하여 분산시간에 따른 입자의 문산 상태를 살펴보았다.

• Korean Chemical Engineering Research
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• v.50 no.4
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• pp.621-626
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• 2012

In this study, the composite coating materials with improved thermal insulation property were prepared by incorporating the hollow micro-spheres with high heat transfer resistance. The UV curable resin system consisting of hexa aliphatic urethane acrylate (UP118), trimethylolpropane triacrylate (TMPTA), 1,6-hexanediol diacrylate (HDDA), and photoinitiator (Irgacure184) was employed as an organic binder. The glass substrates were coated by the prepared composites via bar coating method and cured under UV radiation. The optical transparency, thermal insulation property, adhesion, and surface hardness of the glass coated with composites containing different type of micro-spheres were investigated. The incorporation of micro-spheres with only 20 vol% of content resulted in remarkable improvement in the thermal insulation property of the coated glass. In addition, the transparent coated glass with light transmittance of about 80% could be obtained when silica micro-sphere (SP) was used as a thermal barrier.

• Composites Research
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• v.26 no.6
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• pp.337-342
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• 2013

The good dispersion of nano-materials in epoxy matrix was important parameter for the reinforcement effect, and the evaluation of dispersion degree was to prove it. This work was studied to predict the dispersion condition of nano-SiC powders in SiC/epoxy composites using capacitance measurement. Capacitance was defined to be the electric capacity in proportional to electron charge of the measuring section. In case of nano-SiC powders, the electron charge of SiC/epoxy composites was higher than that of neat epoxy resin. Capacitance was evaluated for each section of SiC/epoxy composites. The prediction of dispersion condition was verified by using capacitance measurement. Dispersion condition of nano-SiC powders in epoxy matrix was evaluated with two different dispersion methods, i.e., sonication and stirring methods. The dispersion degree was also verified with the tensile strength correlating to capacitance.

• Polymer(Korea)
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• v.25 no.1
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• pp.122-132
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• 2001

Thermoplastic film infusion process was investigated by using a rubber tool, which intrinsically contains a thermally-expandable characteristic and effectively compensates for the pressure loss caused by thermoplastic polymer infusion. Increasing temperature up to the melting temperature of matrix, the polymer melt subsequently infused into the dry fabric, but the pressure was successfully sustained by the rubber tool. Even with the decreased resin volume, the rubber tool produced sufficiently high elastic force for continuous resin infusion. Combining D'Arcy's law with the compressibility of rubber tool and elastic fiber bed, a film infusion model was developed to predict the resin infusion rate and pressure change as a function of time. In addition, the film infusion process without the rubber tool was viewed and analyzed by a compression process of the elastic fiber bed and viscous resin melt. The compressibility of fiber bed was experimentally measured and the multiple-step resin infusion was well described by the developed model equations.

• Polymer(Korea)
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• v.27 no.1
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• pp.52-60
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• 2003

In this work, two types of Ni-plating, namely electrolytical and electroless Ni-platings on carbon fiber surfaces, were carried out to enhance the impact resistance of composites. And the comparison between electrolytical and electroless methods on their impact properties of composite system was studied. The surface properties of carbon fibers were characterized using XRD, SEM, and contact angle measurements. The impact behaviors were investigated using an Izod type impact tester. As experimental results, it was observed that electrolessly plated Ni layers had Ni-P alloys on carbon fiber surfaces as revealed by XRD, and electrolytically Ni-plated carbon fibers showed higher surface free energies than those of the electrolessly Ni-plated carbon fibers. In particular, the impact strengths of electrolessly Ni-plated carbon fibers-reinforced plastics were strongly increased. These results were probably due to the difference of wettabilities according to the different types of Ni-plating methods.

• Composites Research
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• v.24 no.5
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• pp.34-38
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• 2011

Carbon nanotubes (CNTs) have been widely investigated as reinforcements of CNT/polymer nanocomposites to enhance mechanical and electrical properties of polymer matrices since their discovery in the early 90's. Furthermore, the number of studies about incorporating CNTs into carbon fiber reinforced plastics (CFRP) to reinforce their polymer matrices is increasing recently. In this study, single-walled carbon nanotubes (SWNT) were dispersed in epoxy with 0.2 wt.% and 0.5 wt.%. Then, the SWNT/epoxy mixtures were processed to carbon fiber composites by a vacuum assisted resin transfer molding (VARTM) and a wet lay up method. The processed composite samples were tested for the interlaminar shear strength (ILSS). The relationship between the interlaminar shear strengths and processing, and the reinforcement mechanism of carbon nanotubes were investigated. CNT/epoxy nanocomposite specimens showed the increased tensile properties. However, the ILSS of carbon fiber composites was not enhanced by reinforcing the matrix with CNTs because of processing issues caused by increased viscosity of the matrix due to addition of CNTs particularly for a VARTM method.