Structural features of jammed-granulate metamaterials

TL;DR

This paper investigates how the microscopic particle properties and packing geometry of jammed-granulate metamaterials influence their macroscopic mechanical behavior, revealing unique deformation and strength characteristics.

Contribution

It introduces the study of the relationship between particle properties, packing protocol, and mechanical response in jammed-granulate metamaterials, highlighting their deformation mechanisms.

Findings

Stiffness depends on volume fraction from creation protocol.

Ultimate strength relates to force network yielding.

Deformation occurs mainly through affine motion with homogeneous plastic events.

Abstract

Granular media near jamming exhibit fascinating properties, which can be harnessed to create jammed-granulate metamaterials: materials whose characteristics arise not only from the shape and material properties of the particles at the microscale, but also from the geometric features of the packing. For the case of a bending beam made from jammed-granulate metamaterial, we study the impact of the particles' properties on the metamaterial's macroscopic mechanical characteristics. We find that the metamaterial's stiffness emerges from its volume fraction, in turn originating from its creation protocol; its ultimate strength corresponds to yielding of the force network. In contrast to many traditional materials, we find that macroscopic deformation occurs mostly through affine motion within the packing, aided by stress relieve through local plastic events, surprisingly homogeneously spread and persistent throughout bending.