Nonlinear response of dense colloidal suspensions under oscillatory shear: Mode-coupling theory and FT-rheology experiments

TL;DR

This paper combines theory, experiments, and simulations to analyze the nonlinear rheological behavior of dense colloidal suspensions under oscillatory shear, revealing the role of yield stress and predicting critical exponents.

Contribution

It introduces a schematic mode-coupling theory that accurately describes nonlinear responses and yield stress phenomena in dense colloids under oscillatory shear, validated by experiments and simulations.

Findings

Nonlinear stress response characterized by higher harmonics.

Prediction of an ideal glass transition with a dynamic yield stress.

Excellent agreement of decay exponents with experiments and simulations.

Abstract

Using a combination of theory, experiment and simulation we investigate the nonlinear response of dense colloidal suspensions to large amplitude oscillatory shear flow. The time-dependent stress response is calculated using a recently developed schematic mode-coupling-type theory describing colloidal suspensions under externally applied flow. For finite strain amplitudes the theory generates a nonlinear response, characterized by significant higher harmonic contributions. An important feature of the theory is the prediction of an ideal glass transition at sufficiently strong coupling, which is accompanied by the discontinuous appearance of a dynamic yield stress. For the oscillatory shear flow under consideration we find that the yield stress plays an important role in determining the non linearity of the time-dependent stress response. Our theoretical findings are strongly supported by both large amplitude oscillatory (LAOS) experiments (with FT-rheology analysis) on suspensions of thermosensitive core-shell particles dispersed in water and Brownian dynamics simulations performed on a two-dimensional binary hard-disc mixture. In particular, theory predicts nontrivial values of the exponents governing the final decay of the storage and loss moduli as a function of strain amplitude which are in excellent agreement with both simulation and experiment. A consistent set of parameters in the presented schematic model achieves to jointly describe linear moduli, nonlinear flow curves and large amplitude oscillatory spectroscopy.