Quasi-2D dynamic jamming in cornstarch suspensions: visualization and force measurements

TL;DR

This study visualizes and measures forces during dynamic jamming in cornstarch suspensions, revealing how jamming fronts propagate and how force responses develop in impact scenarios.

Contribution

It provides new insights into the propagation of jamming fronts and force development in cornstarch suspensions under impact, combining visualization with force measurements.

Findings

Jamming fronts propagate in axial and transverse directions with a 2:1 ratio.

Force response initially explained by added mass, then deviates after boundary contact.

Delay in force response corresponds to development of uniform velocity gradient.

Abstract

We report experiments investigating jamming fronts in a floating layer of cornstarch suspension. The suspension has a packing fraction close to jamming, which dynamically turns into a solid when impacted at a high speed. We show that the front propagates in both axial and transverse direction from the point of impact, with a constant ratio between the two directions of propagation of approximately 2. Inside the jammed solid, we observe an additional compression, which results from the increasing stress as the solid grows. During the initial growth of the jammed solid, we measure a force response that can be completely accounted for by added mass. Only once the jamming front reaches a boundary, the added mass cannot account for the measured force anymore. We do not, however, immediately see a strong force response as we would expect when compressing a jammed packing. Instead, we observe a delay in the force response on the pusher, which corresponds to the time it takes for the system to develop a close to uniform velocity gradient that spans the complete system.