Measuring order in the isotropic packing of elastic rods

TL;DR

This paper investigates the degree of order in 2D elastic rod packings under isotropic confinement by measuring layering and compressibility, aiming to develop a statistical understanding of such disordered systems.

Contribution

It introduces a controlled experimental setup to quantify order and mechanical properties in elastic rod packings, providing new metrics for their analysis.

Findings

Number of superposed layers as an order measure

Effective compressibility of the configuration

Potential for a statistical framework for elastic packings

Abstract

The packing of elastic bodies has emerged as a paradigm for the study of macroscopic disordered systems. However, progress is hampered by the lack of controlled experiments. Here we consider a model experiment for the isotropic two-dimensional confinement of a rod by a central force. We seek to measure how ordered is a folded configuration and we identify two key quantities. A geometrical characterization is given by the number of superposed layers in the configuration. Using temporal modulations of the confining force, we probe the mechanical properties of the configuration and we define and measure its effective compressibility. These two quantities may be used to build a statistical framework for packed elastic systems.