Migration and orientation of disk-like particles in microcomposite processing

The objective of this study is to well understand the migration and orientation of thin micro-particles, such as talc and mica, in a suspension flow by means of both experiments and numerical simulations as well as to obtain the knowledge of the processing operations of thin micro-particle reinforced composites. A slit channel was mounted on the sidewall of a large reservoir in the experimental setup. For this reason, the thin disk-like particles were subjected by a planar extensional flow in a reservoir, then by a simple shear flow through a slit channel. The evolution of the orientation of thin disk-like particles was studied in both a planar extensional and simple shear flows by numerical calculation of the Jeffery equation: thin disk-like particles aligned in the parallel orientation to the upper- and lower-walls of the slit channel in a planar extensional flow through the reservoir, then entered into the inlet of the slit channel. On the other hand, in a simple shear flow through the slit channel, the disk-like particles kept this parallel orientation except the occurrence of flip-over. The period of the flip-over became longer with a decrease in aspect ratio (thickness/diameter) of the disk-like particles. Furthermore, the measurements of the orientation of the talc particles in a suspension flow through the slit channel clearly showed that almost the same period of the flip-over was found in spite of different particle size. The experimental result arises from complex geometries and no accurate data of the thickness of talc particles.