Microscopic dynamics and failure precursors of a gel under mechanical load

TL;DR

This study reveals that microscopic dynamics in a colloidal gel undergo significant changes before macroscopic failure, with measurable precursors identified through combined light scattering and rheology techniques.

Contribution

It introduces an original experimental setup that links microscopic particle dynamics to macroscopic failure in gels, highlighting precursors to failure.

Findings

Microscopic dynamics change dramatically before failure.

Reversible displacements shift to irreversible rearrangements.

Precursors can be detected thousands of seconds prior to failure.

Abstract

Material failure is ubiquitous, with implications from geology to everyday life and material science. It often involves sudden, unpredictable events, with little or no macroscopically detectable precursors. A deeper understanding of the microscopic mechanisms eventually leading to failure is clearly required, but experiments remain scarce. Here, we show that the microscopic dynamics of a colloidal gel, a model network-forming system, exhibit dramatic changes that precede its macroscopic failure by thousands of seconds. Using an original setup coupling light scattering and rheology, we simultaneously measure the macroscopic deformation and the microscopic dynamics of the gel, while applying a constant shear stress. We show that the network failure is preceded by qualitative and quantitative changes of the dynamics, from reversible particle displacements to a burst of irreversible plastic rearrangements.