Migration and orientation of disk-like particles in microcomposite processing

Abstract

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.

Keywords

disk-like particle / talc particle suspension / orientation of thin particle / planar extensional flow / simple shear flow

References

[1] PipesR. B., McculloughR. L., TaggartD. G.. Behavior of discontinuous fiber composites: fiber orientation[J]. Polym Composites, 1982, 3: 34-39

[2] MaitiS. N., SharmaK. K.. Studies on polypropylene composites filled with talc particles, Part I. Mechanical properties[J]. J Mater Sci, 1992, 27: 4605-4613

[3] KarradS., Lopez CurestaJ. M., CrespyA.. Influence of a fine talc on the properties of composites with high density polyethylene and polyethylene/polystyrene blends[J]. J Mater Sci, 1998, 33: 453-461

[4] McinerneyL. F., KaoN., BhattacharyaS. N.. Melt strength and extensibility of talc-filled polypropylene[J]. Polym Eng Sci, 2003, 43: 1821-1829

[5] WhiteJ. L., KnutssonB. A.. Theory of thermal conductivity, heat conduction and convective heat transfer in fiber filled polymer composites[J]. Polym Eng Rev, 1982, 2: 71-82

[6] MartinssonJ., WhiteJ. L.. Characteristics of thermoplastics containing electrically conducting asymmetric particles: anisotropic electrical conductivity of injection molded parts and extrusion behavior[J]. Polym Composites, 1986, 7: 302-314

[7] LimS. H., WhiteJ. L.. Development and characterization of orientation of anisotropic disk and fibrous particles in a thermoplastic matrix[J]. J Rheol, 1990, 34: 343-366

[8] JefferyG. B.. The motion of ellipsoidal particles immersed in a viscous fluid[J]. Proc R Soc, 1922, A102: 161-179