New analysis and correlation between steady and oscillatory tests in fumed silica-based shear thickening fluids

Abstract

In recent years, the non-Newtonian behavior of shear thickening fluids (STFs) has motivated a sharp increase in the number of studies related to their use for engineering applications. For this reason, rheological characterization of STFs is crucial in order to develop and design new devices based on these novelsmart fluids. Typically, different experiments have been carried out for the rheological characterization of STFs to prove their shear/strain thickening behavior. In order to find an empirical relationship between steady and oscillatory experiments, the modified Cox-Merz rule has been recently used to correlate the results with enormous controversy between authors due to the disparity in the correlations achieved. In this paper, we present an improvement in the correlation between the results obtained in steady and oscillatory tests in STFs using fumed silica-concentrated suspensions. The proposed method with the use of strain sweep oscillatory tests has improved the correlation in all STF regimes (pre-transition, transition, and post-transition) in comparison with the results obtained using the modified Cox-Merz rule, which uses oscillatory frequency sweep tests. This improvement has been experimentally validated using concentrated colloidal suspensions with different concentrations of fumed silica (from 12.5 to 25 wt%). Rheological experiments with shear thickening fluids performed in this article.