Micromechanical origin of plasticity and hysteresis in nest-like packings

TL;DR

This paper investigates how the microscopic interactions and contact dynamics of fibers in disordered packings lead to macroscopic phenomena like plasticity and hysteresis, with implications for materials like textiles and bird nests.

Contribution

It reveals the micromechanical origins of plasticity and hysteresis in fiber packings through experimental and computational analysis of contact behavior.

Findings

Non-linear stiffness observed during cyclic compression.

Transient plasticity linked to contact rearrangements.

Hysteresis is velocity-independent and repeatable.

Abstract

Disordered packings of unbonded, semiflexible fibers represent a class of materials spanning contexts and scales. From twig-based bird nests to unwoven textiles, bulk mechanics of disparate systems emerge from the bending of constituent slender elements about impermanent contacts. In experimental and computational packings of wooden sticks, we identify prominent features of their response to cyclic oedometric compression: non-linear stiffness, transient plasticity, and eventually repeatable velocity-independent hysteresis. We trace these features to their micromechanic origins, identified in characteristic appearance, disappearance, and displacement of internal contacts.