A cohesive granular material with tunable elasticity

TL;DR

This paper introduces a customizable cohesive granular material made from glass beads and a curable polymer, allowing precise control over elasticity and failure mechanisms, useful for modeling geological and biological porous systems.

Contribution

It presents a novel, tunable cohesive granular medium with adjustable elasticity and failure properties, created by mixing beads with a curable polymer, and investigates its mechanical behavior and failure mechanisms.

Findings

Elastic response varies over several orders of magnitude with bridge and particle size.

Linear-elastic regime ends at about 8% strain, indicating shear failure onset.

Material's tunability makes it suitable for modeling geological and biological porous media.

Abstract

By mixing glass beads with a curable polymer we create a well-defined cohesive granular medium, held together by solidified, and hence elastic, capillary bridges. This material has a geometry similar to a wet packing of beads, but with an additional control over the elasticity of the bonds holding the particles together. We show that its mechanical response can be varied over several orders of magnitude by adjusting the size and stiffness of the bridges, and the size of the particles. We also investigate its mechanism of failure under unconfined uniaxial compression in combination with in situ x-ray microtomography. We show that a broad linear-elastic regime ends at a limiting strain of about 8%, whatever the stiffness of the agglomerate, which corresponds to the beginning of shear failure. The possibility to finely tune the stiffness, size and shape of this simple material makes it an ideal model system for investigations on, for example, fracturing of porous rocks, seismology, or root growth in cohesive porous media.