Comparison of rheological behaviors with fumed silica-based shear thickening fluids

Shear thickening fluids (STFs) of differing compositions were fabricated and characterised in order to observe the effect of varying chemical and material properties on the resultant rheological behavior. Steady shear tests showed that for a given carrier fluid and particle size exists an optimum weight fraction which exhibits optimal shear thickening performance. Testing also showed that increasing particle size resulted in increased shear thickening performance and its onset whilst altering the carrier fluid chemistry has a significant effect on the thickening performance. An explanation is provided connecting the effect of varying particle size, carrier fluid chemistry and weight fraction to the resultant rheological behavior of the STFs. Two STFs were chosen for further testing due to their improved but contrasting rheological behaviors. Both STFs displayed a relationship between steady and dynamic shear conditions via the Modified Cox-Merz rule at high strain amplitudes (γ≥500%). Understanding the effects of particle and liquid polymer chemistry on the shear thickening effect will assist in ‘tailoring’ STFs for certain potential or existing applications.