Viscous-like forces control the impact response of shear-thickening dense suspensions

TL;DR

This study demonstrates that viscous-like forces, rather than added-mass effects, dominate the impact response of shear-thickening dense suspensions, supported by experiments and numerical modeling.

Contribution

It introduces viscous-like forces into impact models for shear-thickening suspensions, challenging the traditional added-mass paradigm.

Findings

Viscous-like forces dominate impact dynamics.

Experimental data align with viscous-like models.

Added-mass model is inconsistent with observed behavior.

Abstract

We experimentally and theoretically study impacts into dense cornstarch and water suspensions. We vary impact speed as well as intruder size, shape, and mass, and we characterize the resulting dynamics using high-speed video and an onboard accelerometer. We numerically solve previously proposed models, most notably the added-mass model as well as a class of {viscous-like} models. In the {viscous-like models}, the intruder dynamics are dominated by {large, viscous-like forces} at the boundary of the jammed front {where large shear rates and accompanying large viscosities are present.} We find that our experimental data are consistent with this class of models and inconsistent with the added mass model. Our results strongly suggest that the added-mass model, which is the dominant model for understanding the dynamics of impact into shear-thickening dense suspensions, should be updated to include these viscous-like forces.