(279c) Dynamic Analysis of Shear Thickening, Concentrated, Colloidal Suspensions

Shear thickening in concentrated suspensions is known to occur via the formation of load bearing hydroclusters from theory, simulations, flow-SANS experiments, and indirect rheological measurements. However, the dynamic behavior of these concentrated suspensions is not well understood. In contrast to the extensive work that has been done on the steady shear behavior of concentrated suspensions. By using a technique known as large amplitude oscillatory shear (LAOS) we will provide a systematic study of the dynamic response of concentrated suspensions at various volume fractions, while also varying particle size and shape. A new analysis technique that examines the stress-strain waveform response in Fourier space will be used to better understand the dynamic behavior of concentrated suspensions. Using this technique a detailed analysis will be provided that will show the onset of shear thinning and shear thickening as well slip that will help in probing the limits of the rheometric device. The energy dissipation of each of the concentrated suspensions will also be shown along with how it depends on volume fraction, particle size and shape.