| Summary: | 碩士 === 中原大學 === 機械工程研究所 === 94 === The fuel cell is one of the extremely potential clean energy. The bipolar plate is an important component in the fuel cell, and its cost has accounted for about 50 to 60% of the whole. Injection molding of the bipolar plate using polymer composite of electric fiber becomes price competitive method and can be mass-produced. At present, there are few research on the relationship between fiber distribution and the electric conductivity for polymer composite with electric fiber using injection molding process.
In this study, there are two designs of mold insert that one is a flat insert, the other is channel insert and the material is polycarbonate blended with 4% carbon fiber. For studying fiber distribution, the bipolar plate was molded using different filling velocity(50 mm/s, 65 mm/s and 80 mm/s) and channel layout direction, and the fiber distribution along the thickness-direction was measured by SEM to investigate the influence of filling velocity and channel layout on distribution. By obtaining the best fiber distribution at the results of previous experiment, influence of filling velocity and channel layout on resistance was investigated using polystyrene blended with 30% carbon fiber. The relationship between fiber distribution and resistance was studied.
As the results, the fiber distribution is uniform at low velocity(50 mm/s), but the low concentrations of conductive fiber appear near gate and at the end of flow for all kinds of filling velocity. As filling velocity raises to 60 mm/s or 80 mm/s, the concentrations graduately reduce from gate to end of flow. Therefore the filling velocity influences fiber distribution. On the channel layout, as channel is perpendicular to filling direction, the fibers are rolled and banded together, and the conductivity can be improved about 50% compared with channel parallel to filling direction. This study can offer guide lines of channel layout and gate position for bipolar.
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