Dense suspensions of particles in a liquid exhibit a number of counter-intuitive, non-Newtonian flow behaviors. Most remarkably, the application of stress can dramatically harden the material, transforming it from a liquid state at rest into a solid-like state when driven hard. Shear-thickening-based models developed over the last 25 years cannot explain the observed large normal stresses (large enough to support a grown person's weight when running across a pool filled with a suspension such as cornstarch in water). This talk surveys some of the key issues, discusses the stress scales associated with shear thickening in dense suspensions, and outlines a new scenario for impact response. In particular, using high-speed video and x-ray imaging during sudden impact, we are able to link the nonlinear suspension dynamics in a new way to the jamming phase transition.
Argonne Physics Division Colloquium Schedule