Early-stage impact dynamics in dense suspensions of millimeter-sized particles

TL;DR

This paper explores the early impact dynamics of dense suspensions with millimeter-sized particles, demonstrating that their impact hardening behavior aligns with Stokes flow predictions and extending understanding beyond micrometer-scale systems.

Contribution

It provides experimental validation of impact-induced hardening in large-particle suspensions and confirms the applicability of the floating model under these conditions.

Findings

Maximum drag force scales as $u_0^{3/2}$ at high impact speeds.

Early-stage behavior matches floating model predictions.

Impact dynamics are similar to micrometer-sized suspensions despite larger particles.

Abstract

This study investigates the phenomenon of the early-stage dynamics of impact-induced hardening in dense suspensions, where materials undergo solidification upon impact. While Stokes flow theory traditionally applies to suspensions with micrometer-sized particles due to their low Reynolds numbers, suspensions containing larger particles defy such idealizations. Our work focuses on the early-stage impact-induced hardening of suspensions containing millimeter-sized particles through dynamic impact experiments. We are particularly interested in the maximum drag force $F_\mathrm{max}$ acting on the projectile as a function of the impact speed $u_0$. We successfully conducted experiments using these suspensions and confirmed the relation $F_\mathrm{max}\sim u_0^{3/2}$ for relatively large $u_0$ as observed in the previous studies suspensions of micrometer-sized particles. Our findings reveal that the early-stage behaviors of millimeter-sized particle suspensions align well with predictions from the floating model, typically applicable under Stokes flow conditions. This research sheds light on the complex dynamics of impact-induced hardening in dense suspensions, particularly with larger particles, advancing our understanding beyond conventional micrometer-sized systems.