Title: Rigidity and failure in granular materials: from the particle to the bulk scale

Author (Invited): Karen Daniels, NC State Univeristy

Abstract:

Granular materials, including those found in geophysical contexts and engineered to specific purposes throughout our built world, are inherently heterogeneous: continuum models of bulk properties often fail to capture the full range of behaviors. One promising alternative is to build an understanding of material properties from measurements at the particle scale. Our lab's experiments make use of idealized, optically birefringent materials to quantify the interparticle forces -- and thereby directly measure the stress tensor at the particle scale -- within compressed or sheared granular materials. I will describe these experimental techniques, the heterogeneous network of forces that they reveal, and what we learn from analyzing systems at the mesoscale. I will talk about several frameworks (network science, rigidity percolation, phonon modes, stress-force-fabric) capable of connecting the internal structure of disordered materials to their rigidity and/or failure under loading, and describe how we are beginning to apply these results to more realistic systems.