Brittle and ductile yielding in soft materials

Area of Science:

• Rheology and soft matter physics.
• Material science and continuum mechanics.

Background:

• Soft materials transition from solid-like to liquid-like states under mechanical stress.
• Understanding yielding behavior is crucial for applications in additive manufacturing, environmental science, and geology.
• Yielding can be gradual (ductile) or abrupt (brittle), with distinct rheological signatures.

Purpose of the Study:

• To introduce a "brittility factor" into a continuum model for yield stress materials.
• To explain the spectrum of yielding behaviors (ductile to brittle) using a unified model.
• To provide a framework for understanding the rate of yielding transitions in soft matter.

Main Methods:

• Development of a continuum model incorporating a new parameter: the brittility factor.
• Analysis of rheological signatures, including stress overshoot and loss modulus changes.
• Comparison of model predictions with experimental data from various yield stress fluids.

Main Results:

• The brittility factor successfully accounts for the spectrum of yielding behaviors in soft materials.
• Increased brittility reduces the contribution of recoverable deformation to plastic deformation, accelerating yielding.
• Model predictions align well with experimental rheological data across different materials.

Conclusions:

• The brittility factor offers a simple yet powerful tool for characterizing yielding in soft materials.
• This parameter is critical in determining the speed of the yielding transition under various loading conditions.
• The model demonstrates broad applicability across diverse yield stress fluids with varying microstructures.