Particle Shape Effects on the Stress Response of Granular Packings

TL;DR

This study investigates how different particle shapes, including convex and non-convex geometries, influence the stress response of granular packings, revealing shape-dependent tuning of mechanical properties.

Contribution

It provides experimental data on stress responses of diverse 3D-printed particle shapes, highlighting shape effects on stiffness and yield behavior in granular materials.

Findings

Particle shape significantly affects stress-strain behavior.

Shape can be used to tune packing stiffness and yield stress.

Confining pressure influences overall mechanical response.

Abstract

We present measurements of the stress response of packings formed from a wide range of particle shapes. Besides spheres these include convex shapes such as the Platonic solids, truncated tetrahedra, and triangular bipyramids, as well as more complex, non-convex geometries such as hexapods with various arm lengths, dolos, and tetrahedral frames. All particles were 3D-printed in hard resin. Well-defined initial packing states were established through preconditioning by cyclic loading under given confinement pressure. Starting from such initial states, stress-strain relationships for axial compression were obtained at four different confining pressures for each particle type. While confining pressure has the largest overall effect on the mechanical response, we find that particle shape controls the details of the stress-strain curves and can be used to tune packing stiffness and yielding. By correlating the experimentally measured values for the effective Young's modulus under compression, yield stress and energy loss during cyclic loading, we identify trends among the various shapes that allow for designing a packing's aggregate behavior.