Prediction of fiber rotation in an orifice channel during injection molding process

Additive alignment in polymer composites can enhance the physical properties of the constitutive material. Researchers have attempted to understand and predict the additive orientation during the fabrication process, such as injection molding. In this study, the rotation of carbon fibers embedded in uncured polydimethylsiloxane flowing in an orifice channel is analyzed via a flow visualization experiment and image processing of obtained images. The angular velocity of additives is correlated with the shear rates in the flow field calculated from the computational fluid dynamics simulation with the assumption of a single-phase and a non-Newtonian flow. The effective shear rate is found to have a larger effect on the rotation of fiber compared with the aspect ratio of the fiber and the initial alignment angle to the flow direction. A correlation between the effective shear rate and angular velocity of the fibers is developed and verified experimentally. This correlation can be used to predict the fiber rotation during polymer composite fabrication within an orifice channel and hence provide useful information regarding the anisotropic physical properties of the final product. (c) 2021 The Society of Rheology.