Direct observation of percolation in the yielding transition of colloidal glasses

When strained beyond the linear regime, soft colloidal glasses yield to steady-state plastic flow in a way that is similar to the deformation of conventional amorphous solids. Plasticity in amorphous materials is associated with irreversible rearrangements of localized and highly strained zones, but the microscopic origin of yielding and plastic flow in soft glassy materials is still unclear. To study how these rearrangements grow and organize in the transient state across yielding, CC&B researchers lead by Stefano Zapperi, in collaboration with experimentalists from the University of Amsterdam, combined confocal microscopy experiments on three-dimensional hard-sphere colloidal glasses with atomistic simulations of metallic glasses and mesoscopic modelling. We identified growing clusters of non-affine deformation percolating at yielding, which indicate that percolation of highly non-affine particles is the hallmark of the yielding transition in disordered glassy systems. This result seems to show a universal critical transition at the yielding of glasses and raises interesting questions on the most appropriate coarse-grained description of the yielding of amorphous solids.

The work was published in Phys. Rev. Lett.

published on 6/16/2017