Anisotropic Particles Strengthen Granular Pillars under Compression

TL;DR

This study investigates how particle shape influences the mechanical response of granular pillars under compression, revealing that anisotropic particles like dimers enhance strength and local structure anisotropy impacts deformation behavior.

Contribution

It introduces a detailed analysis of how different particle shapes affect granular pillar strength and local structural anisotropies during compression.

Findings

Dimers significantly strengthen the granular pillar.

Initial orientational order influences the strengthening effect.

Local structure anisotropies are robust despite void formation.

Abstract

We probe the effects of particle shape on the global and local behavior of a two-dimensional granular pillar, acting as a proxy for a disordered solid, under uniaxial compression. This geometry allows for direct measurement of global material response, as well as tracking of all individual particle trajectories. In general, drawing connections between local structure and local dynamics can be challenging in amorphous materials due to lower precision of atomic positions, so this study aims to elucidate such connections. We vary local interactions by using three different particle shapes: discrete circular grains (monomers), pairs of grains bonded together (dimers), and groups of three bonded in a triangle (trimers). We find that dimers substantially strengthen the pillar and the degree of this effect is determined by orientational order in the initial condition. In addition, while the three particle shapes form void regions at distinct rates, we find that anisotropies in the local amorphous structure remain robust through the definition of a metric that quantifies packing anisotropy. Finally, we highlight connections between local deformation rates and local structure.