Flow Induced Rigidity Percolation in Shear Thickening Suspensions

Discontinuous shear thickening (DST) is associated with a sharp rise in a suspension's viscosity with increasing applied shear rate or stress. Key signatures of DST, highlighted in recent studies, are the very large fluctuations of the measured stress as the suspension thickens with increasing rate. A clear link between microstructural development and the dramatic increase in stress fluctuations has not been established yet. To identify the microstructural underpinnings of this behavior, we perform simulations of sheared dense suspensions. Through an analysis of the particle contact network, we identify a subset of constrained particles that contributes directly to the rapid rise in viscosity and large stress fluctuations. Indeed, both phenomena can be explained by the growth and percolation of constrained particle networks-in direct analogy to rigidity percolation. A finite size scaling analysis confirms this to be a percolation phenomenon and allows us to estimate the critical exponents. Our findings reveal the specific microstructural self-organization transition that underlies DST.