• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.88-91
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• 2011

Glass fiber drawing from a silica preform is one of the most important processes in optical fiber manufacturing. High purify silica preform of cylindrical shape is fed into the graphite furnace, and then a very thin glass fiber of 125 micron diameter is drawn from the softened and heated preform. A computational analysis is performed to investigate the heat transfer characteristics of preform heating and the glass fiber drawing in the furnace. In addition to the dominant radiative heating of preform by the heating element in the furnace, present analysis also includes the convective heat transport by the gas flowing around the preform that experiences neck-dawn profile and the freshly drawn glass fiber at high fiber drawing speed. The computational results present the effects of gas flow on the temperature of preform and glass fiber as well as the neck-down profile of preform.

• Journal of computational fluids engineering
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• v.16 no.1
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• pp.22-29
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• 2011

In this study, the glass fiber drawing from a silica preform in the furnace for the optical fiber manufacturing process is numerically simulated by considering the radiative heating of cylindrically shaped preform. The one-dimensional governing equations of the mass, momentum, and energy conservation for the heated and softened preform are solved as a set of the boundary value problems along with the radiative transfer approximation between the muffle tube and the deformed preform shape, while the furnace heating is modeled by prescribing the temperature distribution of muffle tube. The temperature-dependent viscosity of silica plays an important role in formation of preform neck-down profile when the glass fiber is drawn at high speed. The calculated neck-down profile of preform and the draw tension are found to be reasonable and comparable to the actual results observed in the optical fiber industry. This paper also presents the effects of key operating parameters such as the muffle tube temperature distribution and the fiber drawing speed on the preform neck-down profile and the draw tension. Draw tension varies drastically even with the small change of furnace heating conditions such as maximum heating temperature and heating width, and the fine adjustment of furnace heating is required in order to maintain the appropriate draw tension of 100~200 g.

• Korea-Australia Rheology Journal
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• v.19 no.1
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• pp.17-25
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• 2007

In liquid composite molding (LCM), composites are produced by impregnation of a dry preform with liquid resin. The resin flow through the preform is usually described by Darcy's law and the permeability tensor must be obtained for filling analysis. While the resin flow in the thickness direction can be neglected for thin parts, the resin flow in the transverse direction is important for thicker parts. However, the transverse permeability of the preform has not been investigated frequently. In this study, the transverse permeability was measured experimentally for five different fiber preforms. In order to verify the experimental results, the measured transverse permeability was compared with numerical results. Five different fiber mats were used in this study: glass fiber woven fabric, aramid fiber woven fabric, glass fiber random mat, glass fiber braided preform, and glass/aramid hybrid braided preform. The anisotropic braided preforms were manufactured by using a three dimensional braiding machine. The pressure was measured at the inlet and outlet positions with pressure transducers.

• Composites Research
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• v.27 no.1
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• pp.31-36
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• 2014

This paper presents the slip behavior of composite fabrics by high speed resin flow in high pressure resin transfer molding. In order to observe the fiber deformation behavior, we constructed the measuring equipment for friction coefficient between fiber and mold, and the monitoring system for deformation of fiber preform in high-pressure RTM process. Coulomb friction coefficient and hydrodynamic friction coefficient between fiber preform and mold were measured and the external force induced by fluid flow causing the deformation of fiber preform was measured. Friction force calculated by friction coefficient and the external force upon fiber deformation were compared, which showed that preform deformation occurred when the external force was bigger than the friction force. The slip behavior of the fiber preform was mainly influenced by the volume fraction of fiber preform and the friction coefficient.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.10a
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• pp.65-67
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• 2002

Resin Transfer Molding(RTM) is increasingly used for producing fiber reinforced polymer composites, the resin has to flow a long distance to impregnate the dry fibers. The measure for the resistance of the fiber preform to the resin flow is the permeability of the fiber preform. Permeability is a key issue in the design of molds and processes and in flow modeling. In this study, permeability measurement for braided preform is presented and compared with the permeability calculated numerically. Experimental techniques being used to measure the permeability are also discussed. Measurement is conducted in radial flow test under constant pressure.

• Journal of computational fluids engineering
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• v.18 no.4
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• pp.69-73
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• 2013

Mass manufacturing of optical fiber includes the process of very thin glass fiber drawing by heating and softening the high purity silica preform and applying the draw tension on the softened tip of preform neck-down profile in a draw furnace. In this computational study, this process is numerically modeled with simplified geometry of the draw furnace which is comprised of essential parts such as concentric graphite heater, muffle tube, and insulation surrounding the heater. The iterative computational scheme is employed between one-dimensional model of neck-down profile prediction and two-dimensional axisymmetric thermo-fluid CFD computation of radiative heating and working gas convection. The computational results show the experimentally observed neck-down profile in heated section of preform, while yielding the reasonable values of draw tension and heater wattage. Also, this study analyzes and discusses the effects of heating conditions such as heater length and temperature on several important aspects of glass fiber drawing process.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.7 s.94
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• pp.1751-1760
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• 1993

The squeeze casting process is considered as an attractive way to form the primary product of near net shape metal matrix composites for wide use in automobile industry. To understand for infiltration limit in squeeze casting processes, the SAFFIL short fiber preform of volume fraction $10%{\sim}23%$ were fabricated by vaccum pumping and speed control press, and the optimal condition for fiber preform fabrication had been experimentally obtained. The composite materials were fabricated by forced infiltration of molten metals such as Al6061, Al7075, pure Al, AC8A, and Al2024. The infiltration distance and deformation of fiber preform are observed, and tensile strength were measured from at the room temperature.

• The Korean Journal of Ceramics
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• v.3 no.4
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• pp.229-234
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• 1997

Silicon carbide-carbon fiber composites have been prepared by partially Infiltrating porous carbon fiber composites with liquid silicon at a reaction temperature of $1670^{\circ}C$. Reaction between molten silicon and the fiber preform yielded silicon carbide-carbon fiber composites composed of aggregates of loosely bonded SiC crystallites of about 10$\mu\textrm{m}$ in size and preserved the appearance of a fiber. In addition, the SiC/C fiber composites had carbon fibers coated with a dense layer consisted of SiC particles of sizes smaller than 1$\mu\textrm{m}$. The physical and mechanical properties of SiC/C fiber composites were discussed in terms of infiltrated pore volume fraction of carbon preform occupied by liquid silicon at the beginning of reaction. Lower bending strength of the SiC/C fiber composites which had a heterogeneous structure in nature, was attributed to the disruption of geometric configuration of the original carbon fiber preform and the formation of the fibrous aggregates of the loosely bonded coarse SiC particles produced by solution-precipitation mechanism.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.05a
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• pp.34-37
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• 2001

This study developed Fiber/Particle Hybrid MMCs and analyzed their mechanical properties. Using $\textrm{Al}_2\textrm{O}_3f$ and $\textrm{Al}_2\textrm{O}_3p$ with the fiber to particle ratio of 1:1, 1:3, 1:5 hybrid preform and MMCs are fabricated. For the analysis of the mechanical properties, three point bending tests were preformed for the preform and tensile test for the MMCs. The experimental results show that the hybrid MMCs can be successfully fabricated using the equipment of fiber preform fabrication system and squeeze casting method. And as the amount of particle in hybrid MMCs increases, the tensile strength, elastic modulus and the volume fraction of reinforcement increases.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.14 no.4
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• pp.307-320
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• 1989

This paper presetns new design of the Modified Chemical Vapor Deposition(MCVD) system for optical fiber preform fabrication. It contains a glass working lathe, raw material supplier and exhaust gas treatment apparatus as fundamental instruments for MCVD process, graded index fiber design, characteristic of process and the experimenta arrangement to measure the refractive index profile of MCVD preforms, respectively. From the investigation results, it is shown that an ideal graded index fiber preform does not exhibit a center dip or bump.