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Flow visualization of additive alignment in polymer matrix depending on location of gate orifice
Do-In Jeong and Dong-Wook Oh

Thermoplastic polymer composites are considered as substitutes for metallic materials because of their advantages in terms of superior corrosion resistance, mass-productivity, lightness, etc. However, their applications are limited owing to their low melting temperature and electrically and thermally insulating characteristics. Numerous experiments are carried out to overcome these limitations and enhance physical properties by analyzing and controlling additive alignment. To achieve enhancement, it is important to understand the rheology of the additive in a polymer matrix and the resulting alignments inside the mold during the molding process. In this study, a flow visualization experiment was carried out to simulate an injection molding process of polymer composites with carbon fiber as an additive. The alignment of carbon fiber is analyzed as it travels through the gate orifice of the mold channel. An experimental device consisting of a ball-milled-carbon-fiber and Polydimethylsiloxane mixture, syringe pump and tubing, high speed camera with microscope, and lighting system is set up to visualize the additive alignment and orientation inside the mold channel. Two configurations of the gate orifice are used as mold channels. The location, length, and angle of additives were calculated by analyzing images acquired through flow visualization experiments. The orientation of fibers is observed to be determined by the relative amplitudes of velocity gradient components. In addition, it was observed that the position of the gate affects the average angle of the additives in the mold channel.

Keywords: Polymer composite, Flow visualization, Fiber alignment, Orifice channel, Shear rate ratio

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