System-spanning dynamically jammed region in response to impact of cornstarch and water suspensions

Abstract

We experimentally characterize the impact response of concentrated suspensions of cornstarch and water. We hypothesize that the dynamically jammed region that propagates ahead of the impactor is responsible for the strong stress response to impact when it spans between solid boundaries. Using surface imaging and particle tracking at the boundary opposite the impactor, we observed that a visible structure and particle flow at the boundary occur with a delay after impact. We show the delay time is about the same time as the the strong stress response, confirming that the strong stress response results from deformation of the dynamically jammed structure once it spans between the impactor and a solid boundary. A characterization of this strong stress response is reported in a companion paper (arXiv:1407.0719). We also elaborate on the structure of the dynamically jammed region once it spans from the impactor to a solid boundary. We observed particle flow in the outer part of the dynamically jammed region at the bottom boundary, with a net transverse displacement of up to about 5\% of the impactor displacement, indicating shear at the boundary. Direct imaging of the surface of the outer part of the dynamically jammed region reveals a change in surface structure that appears the same as the result of dilation in other cornstarch suspensions. Imaging also reveals cracks, like a brittle solid. These observations suggest the dynamically jammed structure can temporarily support stress according to an effective modulus, like a soil or dense granular material, along a network of frictional contacts between the impactor and solid boundary.

This was originally part of a separate paper (arXiv:1407.0719v3), before being split off as its own paper

References in corpus (8)

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Cited by in corpus (13)

• Testing constitutive relations by running and walking on cornstarch and water suspensions
• Dilatancy in dense suspensions of model hard-sphere-like colloids under shear and extensional flow
• Simulation of dense non-Brownian suspensions with the lattice Boltzmann method: Shear jammed and fragile states
• Intermittent dilation and its coupling to stress in discontinuous shear thickening suspensions
• Impact-induced hardening in dense frictional suspensions
• Emergence of transient reverse fingers during radial displacement of a shear-thickening fluid
• Viscous-like forces control the impact response of shear-thickening dense suspensions
• Unsteady flow, clusters and bands in a model shear-thickening fluid
• Bouncing of a projectile impacting a dense potato-starch suspension layer
• Characterizing the surface texture of a dense suspension undergoing dynamic jamming
• Viscoelastic response of impact process on dense suspensions
• Dynamic jamming of dense suspensions under tilted impact
• Collision of Dynamic Jamming Fronts in a Dense Suspension