Abstract: Fumed silica suspensions in polyethylene glycol (PEG200) exhibited shear-thickening behavior under dynamic oscillatory strain amplitude. Two regimes of shear-thickening behavior were obtained: the first occured at critical strain amplitude γc and different constant frequencies, and the second occured at critical frequency and constant strain amplitude γ0=500%. For the first, the relationships of both of the moduli (G’ and G’’) versus strain amplitude were investigated. The strain amplitude as a function of different constant frequencies was observed. In the linear viscoelastic region, the storage (G’) and the loss (G’’)moduli depended stronglyon frequencywith the power-law: G’∝ω0.57, G’’∝ω0.7. In the second regime, the moduli (G’ and G’’) and complex viscosity η* showed strong dependence on frequency. The behaviors could be qualitatively explained using the cluster theory, which attributed the phenomena to the formation of metastable, flow induced clusters.

Key words: Fumed silica suspensions, Shear-thickening, Storage modulus, Loss modulus, Frequency