Orientation of Disk-like Particles in a Microcomposite Processing

The objective of this study is to well understand the migration and orientation of thin micro-particles in a suspension flow by means of both experiments and numerical simulations. In this framework, the evolution of the orientation of thin micro-particles such as talc and mica, which were modeled by a disk-like particle, in a flow through a slit channel was analyzed to obtain the knowledge of the processing operations of thin micro-particle reinforced composites.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 in the experimental apparatus used. The evolution of the orientation of thin disk-like particles was, therefore, studied in both a planar extensional and simple shear flows by numerical calculation of the Jeffery equation: thin disk-like particles aligned in a parallel orientation to 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 a flip-over phenomenon. The period of the flip-over became longer with a decrease in the aspect ratio 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 although the particle size was different. These experimental results arise from complex geometries and no accurate data of the thickness of the talc particles.