Paper Number
PO23 

Session
Poster Session

Title
Introducing the role of brittility to the soft materials

Presentation Date and Time
October 13, 2021 (Wednesday) 6:30

Track / Room
Poster Session / Ballroom 1-2-3-4

Authors (Click on name to view author profile)

1. Kamani, Krutarth M. (University of Illinois at Urbana-Champaign, Department of Chemical and Biomolecular Engineering)
2. Rogers, Simon A. (University of Illinois at Urbana-Champaign, Department of Chemical and Biomolecular Engineering)

Author and Affiliation Lines (in printed abstract book)
Krutarth M. Kamani and Simon A. Rogers
Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801

Speaker / Presenter 
Kamani, Krutarth M.

Keywords
experimental methods; theoretical methods; additive manufacturing; applied rheology; biological materials; colloids; emulsions; gels; glasses; granular materials; non-Newtonian fluids; rheology methods

Text of Abstract
Many soft materials show the transition from solid-like behavior to liquid-like behavior, but how this yielding transition occurs can vary significantly. Understanding the physics behind this transition is of great interest for the behavior of biological, environmental, and industrial materials, including those used as inks in additive manufacturing. For some materials, the yielding transition is smooth and gradual while others yield abruptly. We refer to this abrupt yielding as being “brittle”. The key signatures of brittle yielding include a stress overshoot in steady-shear-startup tests and a sharp increase in loss modulus during oscillatory tests. We are able to account for brittility in our recently proposed continuum model for yield stress materials (Kamani et al., Phys. Rev. Lett. 126, (2021)). The original formulation of the model describes the unrecoverable plastic viscosity as being dependent on the total strain rate; plastic flow is aided by the rate at which elastic deformation is acquired. We account for brittility by modifying the contribution of the recoverable component to the total strain rate, which impacts the rate at which yielding occurs. The model results are successfully compared to results of different rheological protocols from a number of model yield stress fluids having different microstructures, indicating the general applicability of the phenomenon of brittility for such soft materials. Our study shows that the brittility of soft materials plays a critical role in determining the rate of yielding transition, and provides a simple tool for understanding its effects under various loading conditions.