Mechanics of randomly packed filaments - The "bird nest" as meta-material

Abstract

Systems of randomly packed, macroscopic elements, from jammed spherical grains to tangled long filaments, represent a broad class of disordered meta-materials with a wide range of applications and manifestations in nature. A "bird nest" presents itself at an interface between hard round grains described by granular physics to long soft filaments, the center of textile material science. All of these randomly packed systems exhibit forms of self-assembly, evident through their robust packing statistics, and share a common elastoplastic response to oedometric compression. In reviewing packing statistics, mechanical response characterization, and consideration of boundary effects, we present a perspective that attempts to establish a link between the bulk and local behavior of a pile of sand and a wad of cotton, demonstrating the nest's relationship with each. Finally, potential directions for impactful applications are outlined.