Abstract
Magnetorheological (MR) fluids are one of smart fluids which can be changed their rheological properties in reversible manner by applying magnetic field. While a shear thickening (ST) fluid is speed-activated non-Newtonian fluid; it possesses a low viscosity until the transition of the critical shear rate where it increases dramatically. Their combination can offer both MR and ST effects. This study focuses on a shear thickening MR fluid (ST-MRF) of which the shear thickening properties would be controlled by applied magnetic field. We fabricated a shear thickening fluid (STF) consisting of nano-sized fumed silica particles suspended in a solvent, ethylene glycol, at 25wt% concentration. And then, the micro-sized carbonyl iron particles with different weight fractions were added to the STF to fabricate the ST-MR fluids. The rheological properties in constant rpm tests and oscillatory tests under different magnetic fields have been measured using a HAAKE RS150 parallel disk rheometer with magnetic circuit. The ST-MR fluids exhibit an abrupt increase of shear stress beyond a critical shear rate and a magnetic field controllability of the shear thickening property.
