Fiber Orientation and Concentration Distribution in Flow of a Concentrated Suspension through a Slit Channel Containing a Circular Obstacle

Distributions of fiber orientation and fiber concentration were measured in the flow of a concentrated fiber suspension (CFS) and a dilute one (DFS) through a slit channel containing a cylinder obstacle. In the present paper, those in the flow are quantitatively estimated by direct observation of fibers in the flow of a concentrated suspension, while those in injection molded parts of fiber-reinforced plastics have been studied qualitatively by many researchers. For the CFS, some fibers rotate in an expansion part between the channel wall and the obstacle and the degree of orientation becomes low. The preferred direction of fibers fluctuates in the downstream region of the expansion part. However, almost all fibers near the centerline downstream of the obstacle orient perfectly along the flow direction. This fiber orientation is induced by an elongational flow near the centerline. Furthermore, the fiber concentration for the DFS shows a flat distribution except near the channel wall, while that for the CFS monotonically increases from the wall toward the centerline.