A new visualization technique for short fibers in a slit flow of fiber suspensions

摘要

A classical method for visualization of transparent fiber sin fiber suspensions using a planar light source is examined by geometrical optics and its defect is revealed. To overcome the defect, a new method using fibers with birefringence is proposed. In the present method the crossed polarizers rotating at a higher speed are introduced to observe the fibers with birefringence nearly oriented in the polarizing directions. As a result, the applicability of this method to the visualization of the fibers in a concentrated fiber suspension flow through a slit channel has been confirmed, and its usefulness for the measurement of the fiber ori- entation and fiber concentration distribution has been demonstrated. Furthermore, our experimental re- lationship of total shear strain vs. Orientation angle in a dilute fiber suspension flow is compared with a theoretical result, and it shows the similar tendency to the theoretical one.