• Journal of the Korean Wood Science and Technology
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• v.42 no.4
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• pp.420-427
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• 2014

The physical and mechanical properties of sawdust-rice husk mixed ceramic were investigated with rice husk mixing ratios. The mixed ceramic board was produced with carbonization and resin impregnated sawdust-rice husk board at high temperature. At the same percentage of resin impregnation condition, density and bending strength of the mixed ceramic board increased with increasing the mixing rates of rice husk, whereas weight loss of the ceramic boards decreased. At the same temperature condition for the carbonization of resin impregnated sawdust-rice husk board, the density and bending strength were the highest with 40% of rice husk mixing ratio.

• The Korean Journal of Rheology
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• v.10 no.4
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• pp.185-194
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• 1998

Flow-induced voids during resin impregnation and poor fiber wetting give serious effects on the mechanical properties of composites in resin transfer molding process. In order to better understand the characteristics of resin flow and to investigate the mechanism of void formation, flow visualization experiment for the resin impregnation was carried out on plain weaving glass fiber mats using silicon oils with various viscosity values. The permeability and the capillary pressure for the fiber mats of different porosities were obtained by measuring the penetration length of the resin with time and with various injection pressure. At low porosity and low operating pressure, the capillary pressure played a significant role in impregnation process. Video-assisted microscopy was used in taking the magnified photograph of the flow front of the resin to investigate the effect of the capillary pressure on the void formation. The results showed that the voids were formed easily when the capillary pressure was relatively high. No voids were detected above the critical capillary number of 2.75$\times$$10^{-3}, and below the critical number the void content increased exponentially with decrease of the capillary number. The content of void formed was independent of the viscosity of the resin. For a given capillary number, the void content reduced with the lower porosity of the fiber mat.

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.246-250
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• 2001

In resin transfer molding (RTM), resin is forced to flow through the fiber perform of inhomogeneous permeability. This inhomogeneity is responsible for the mismatch of resin velocity within and between the fiber tows. The capillary pressure of the fiber tows exacerbates the spatial variation of the resin velocity. The resulting microscopic perturbations of resin velocity at the flow front allow numerous air voids to form. In this study, a mathematical model was developed to predict the formation and migration of micro-voids during resin transfer molding. A transport equation was employed to account for the migration of voids between fiber tows. Incorporating the proposed model into a resin flow simulator, the volumetric content of micro-voids in the preform could be obtained during the simulation of resin impregnation.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.5
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• pp.806-811
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• 2013

In this study, to prevent the nonhomogeneity of fiber orientation during the molding of GFRP composites, GFRP prepreg was fabricated using roving fiber and polypropylene resin. Analyses on the degree of impregnation, tensile strength, and microstructure were conducted on the fabricated prepregs. A lower pulling speed, higher resin temperature, and longer die length showed a greater degree of impregnation of the prepreg. The scanning electron microscope (SEM) micrograph showed, a homogeneous fiber orientation. As a result, fundamental techniques for improved productivity were suggested for the manufacturing field.

• Carbon letters
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• v.15 no.2
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• pp.142-145
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• 2014

Isotropic synthetic graphite scrap and phenolic resin were mixed, and the mixed powder was formed at 300 MPa to produce a green body. New bulk graphite was produced by carbonizing the green body at $700^{\circ}C$, and the bulk graphite thus produced was impregnated with resin and re-carbonized at $700^{\circ}C$. The bulk density of the bulk graphite was $1.29g/cm^3$, and the porosity of the open pores was 29.8%. After one impregnation, the density increased to $1.44g/cm^3$ while the porosity decreased to 25.2%. Differences in the pore distribution before and after impregnation were easily confirmed by observing the microstructure. In addition, by using an X-ray diffractometer, the degrees-of-alignment (Da) were obtained for one side perpendicular to the direction of compression molding of the bulk graphite (the "top-face"), and one side parallel to the direction of compression molding (the "side-face"). The anisotropy ratio calculated from the Da-values obtained was 1.13, which indicates comparatively good isotropy.

• Carbon letters
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• v.16 no.2
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• pp.132-134
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• 2015

When manufacturing bulk graphite, pores develop within the bulk during the carbonization process due to the volatile components of the fillers and the binders. As a result, the physical properties of bulk graphite are inferior to the theoretical values. Impregnants are impregnated into the pores generated in the carbonization process through pressurization and/or depressurization. The physical properties of bulk graphite that has undergone impregnation and re-carbonization processes are outstanding. In the present study, a green body was manufactured by molding with natural graphite flakes and phenolic resin at 45 MPa. Bulk graphite was manufactured by carbonizing the green body at 700 and it was subsequently impregnated with impregnants having viscosity of 25.0 cP, 10.3 cP, and 5.1 cP, and the samples were re-carbonized at $700^{\circ}C$. The above process was repeated three times. The open porosity of bulk graphite after the final process was 22.25%, 19.86%, and 18.58% in the cases of using the impregnant with viscosity of 25.0 cP, 10.3 cP, and 5.1 cP, respectively.

• Proceedings of the Korean Ceranic Society Conference
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• 2003.04a
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• pp.27.1-27
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• 2003

• Proceedings of the Korean Ceranic Society Conference
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• 2002.10a
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• pp.74.2-74
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• 2002

• Journal of the Korea Furniture Society
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• v.17 no.1
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• pp.83-89
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• 2006

Because the surface of pine wood is very soft, there have been many attempts, like as surface coating, resin impregnation, and densificationt, to harden the surface of wood for its interior use. This study was carried out for surface hardening of pine wood by laminating of melamine resin sheet. The effect of laminating method on the characteristics of melamine resin sheet-laminated wood(MLW) was investigated. Flat-sawn softwoods were suitable for MLW making. And the pre-drying of wood at $105^{\circ}C$ for 30min, before laminating, was effective for preparing of defect-free MLW. The abrasion resistance of pine wood was greatly improved by laminating of melamine resin sheet on its surface. Consequently, the laminating of melamine resin sheet was proved to be a favorable method for improvement of surface abrasiveness of pine wood.

• Journal of the Korean Wood Science and Technology
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• v.44 no.1
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• pp.106-112
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• 2016

This study investigated electrical properties and far-infrared ray emission according to the carbonizing temperature and phenol-formaldehyde (PF) resin impregnation ratio of ceramics manufactured using sawdust and rice husk. The far-infrared ray emission values and emission energy values decreased as the carbonizing temperature increased. The far-infrared ray emission values of the ceramics manufactured using a carbonizing process at $600^{\circ}C$ and a board with a PF resin impregnation ratio of 60 percent was 0.930; the emission energy presented the highest value of $4.32{\times}10w/m^2$. The electric resistance decreased as the carbonizing temperature increased. For the increase in the carbonizing temperature above $1200^{\circ}C$, ceramics was very close to a conductor due to the small resistance. The power consumption increased by the decrease of electric resistance and increase of the electric current in the case of a higher resin impregnation ratio.