Cyclically sheared colloidal gels: structural change and delayed failure time

TL;DR

This study investigates how cyclic shear affects colloidal gels' structure and stability, revealing structural reorganization, strain-hardening, and anisotropic features that enhance gel stability under stress.

Contribution

It combines experiments and simulations to show how cyclic shear induces structural changes and enhances stability in colloidal gels, highlighting the role of anisotropy.

Findings

Cyclic shear causes structural reorganization in gels.

Strain-hardening increases gel stability.

Shear orientation influences structural imprinting.

Abstract

We present experiments and simulations on cyclically sheared colloidal gels, and probe their behaviour on several different length scales. The shearing induces structural changes in the experimental gel, changing particles' neighborhoods and reorganizing the mesoscopic pores. These results are mirrored in computer simulations of a model gel-former, which show how the material evolves down the energy landscape under shearing, for small strains. By systematic variation of simulation parameters, we characterise the structural and mechanical changes that take place under shear, including both yielding and strain-hardening. We simulate creeping flow under constant shear stress, for gels that were previously subject to cyclic shear, showing that strain-hardening also increases gel stability. This response depends on the orientation of the applied shear stress, revealing that the cyclic shear imprints anisotropic structural features into the gel.