Analysis of the shear thickening behavior of a fumed silica suspension using QL-LAOS approach

The feasibility of applying quasi-linear large amplitude oscillatory shear (QL-LAOS) approach to a shear thickening (ST) fumed silica suspension was tested. While the characteristic time has been used as the parameter for the original QL-LAOS analysis of shear thinning fluids, we obtained that a description based upon increasing stiffness is more appropriate for ST fumed silica suspensions. Very low (<= 1.5) third to first harmonics ratio were obtained indicating the need of alternative criteria to identify QL-LAOS behavior in ST suspensions. Consequently, a method based upon the best fit of an ellipse to the experimental Lissajous-Bowditch curves was proposed. Compliances were obtained from areas of viscous and elastic fitted ellipses. The dependence of the material functions obtained by using a Jeffrey's mechanical viscoelastic framework with angular frequency supports the idea of ST microstructure evolves by increasing with shear the number of small hydroclusters.