Pre- and post-transition behavior of shear-thickening fluids in oscillating shear
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The dynamic shear-thickening behavior of concentrated colloidal suspensions of fumed silica in polypropylene glycol has been investigated. Dynamic frequency sweeps showed that, for any given solids concentration, the complex viscosity at different imposed strain amplitudes followed a unique power-law-type behavior up to the onset of strain thickening. Moreover, similar behavior was also observed in the post-transition state, i.e., the viscosities again superimposed at frequencies beyond the transition frequency. In an attempt to develop a parametric description of this behavior, both the Delaware–Rutgers rule and the concept of a critical shear stress for the onset of shear thickening in steady-state experiments were considered. However, neither approach could account for the observed trends over the entire range of strains and frequency investigated. Plots of the critical shear strains for the onset and the end-point of the transition as a function of frequency were, therefore, used to describe the state of the suspensions for an arbitrary combination of strain and frequency. Finally, Fourier transform (FT) rheology was used to evaluate the extent of non-linearity in the response of the suspensions to dynamic shear, and it was shown that the observed behavior was not significantly influenced by wall slip at the tool–specimen interface.
KeywordsShear thickening LAOS Silica suspension FT rheology
The authors gratefully acknowledge the Sports and Rehabilitation Engineering (SRE) program of the EPFL for the financial support, Prof. Norman J. Wagner and his group at the University of Delaware for numerous discussions of shear-thickening rheology, and Degussa for supplying the materials. They also acknowledge Lars E. Schmidt from LTC for fruitful discussions of FT rheology.
- Clarke B (1967) Rheology of coarse settling suspensions. Trans Inst Chem Eng 45:251–256Google Scholar
- Fischer C, Fauve M, Combaz E, Bourban P-E, Michaud V, Plummer JG, Rhyner H, Månson J-AE (2006b) Dynamic properties of materials for alpine skis. In: Moritz EF, Haake S (eds) The engineering of sports 6, vol. 1. Springer, Berlin Heidelberg New York, pp 263–268Google Scholar
- Hoffmann RL (1972) Discontinuous and dilatant viscosity behavior in concentrated suspensions i. observation of a flow instability. J Colloid Interface Sci 16:155–173Google Scholar
- Hyun K, Nam JG, Wilhelm M, Ahn KH, Lee SJ (2003) Nonlinear response of complex fluids under LAOS (large amplitude oscillatory shear) flow. Korea–Aust Rheol J 15:97–105Google Scholar
- Lee YS, Wagner NJ (2003) Dynamic properties of shear thickening colloidal suspensions. Rheol Acta 42:199–208Google Scholar
- Mewis J, Biebaut G (2001) Shear thickening in steady and superposition flows effect of particle interaction forces. J Rheol 40:9–16Google Scholar