(414c) Shear-Induced Structural Ordering in Jammed Suspensions of Soft Particle Glasses

We computationally show that jammed suspensions of soft particles can form a variety of ordered microstructures and varying macroscopic properties as a function of the degree of polydispersity and volume fraction of particles. A three-dimensional particle-dynamics simulation of the micromechanics of the flow (Seth et al. Nat. Mater. 10, 838 (2011) is employed to elucidate the effect of shear flow on the microstructure of suspensions that are composed of polydispersed particles. Simulations show that polydispersed jammed glasses in shear flow can undergo a structural transitions regardless of the volume fraction of particles. During the transition, the microstructure changes from a glass to a layer-like phase that results in a reduction of the shear stress and elastic energy. The onset shear rate of this transition depends on the volume fraction and degree of polydispersity. Furthermore, there is an induction strain prior to this transition which forms layer-like structures parallel to the flow-vorticity plane. The length of the induction strain decreases with shear rate, which suggests that the structural transition is a shear-activated process. In the case of monodispersed and suspensions with a low degree of polydispersity, shear flow rearranges particles in a hexagonal close-pack (HCP) phase at higher shear rates, while the structure becomes face-centered cubic (FCC) phase at lower shear rates. Simulation tools are used to describe the origin of these phase transitions, and a state diagram of these suspensions that can be utilized to predict the state of a given jammed suspension in shear flow is provided.