Can we reconcile Steady State Rheology with Impact Dynamics for Shear Thickening Suspensions?

Discontinuous Shear Thickening (DST) suspensions behave as typical liquids at low shear rates but exhibit solid-like features, e.g. resistance to flow and cracking, beyond a critical shear rate in steady-state rheology. A standard assumption is that stress measured in rheometer measurements can be used to predict flows in other geometries. The maximum stresses supported by a sample beyond the critical shear rate is O (10^3) Pa in a rheometer. In contrast, DST suspensions can support larger stresses of O (10^6) Pa under impact. Recent impact studies reveal a dynamically jammed region below the impactor. We find that the front velocity of this region is nearly the same as the impact velocity up until a critical impact velocity. Beyond this critical velocity, we find that the front velocity increases with the impact velocity before hitting a plateau. We further investigate the relationship between the critical velocity from impact experiments and the critical shear rate from rheology measurements in an effort to understand the mismatch in the stress scales.