Instability Reveals Clustering in Cohesive Granular Matter

Abstract

We lately reported on a periodic pattern which spontaneously forms at the surface of a thin layer of a cohesive granular material submitted to in-plane stretching [1] or to bending [2]. The mechanism responsible for the instability is the strain softening exhibited by humid granular materials above a typical strain. The present short article gives the opportunity to review the potential physical origin of the cohesion in granular materials and, then, to discuss one experimental example which points out the fundamental role played by the clustering in the mechanical response of the cohesive materials.