  Granular materials show inhomogeneous flows characterized by strain
localization. When strain is localized in a sheared granular material, rigid
regions of a nearly undeformed state are separated by shear bands, where the
material yields and flows. The characteristics of the shear bands are
determined by the geometry of the system, the micromechanical material
properties, and the kinematics at the particle level. For a split-bottom shear
cell, recent experimental work has shown that mixtures of hard, frictional and
soft, nearly frictionless particles exhibit wider shear zones than samples with
only one of the two components. To explain this finding, we investigate the
shear zone properties and the stress response of granular mixtures using
discrete element simulations. We show that both interparticle friction and
elastic modulus determine the shear-band properties of granular mixtures of
various mixing ratios, but their stress response depends strongly on the
interparticle friction. Our study provides a fundamental understanding of the
micromechanics of shear band formation in granular mixtures.
