Micromechanical origin of plasticity and hysteresis in nest-like packings

Disordered packings of unbonded filaments form a unique class of meta-materials, where the mechanics derive from the bending of constituent elements between frictional contacts. We probe the mechanical responses of one such instance, a tangle of wooden sticks in a cylindrical container under cyclic compression, both experimentally and in-silico. We find two prominent features in stress-strain curves' evolution: initial cycles of irreversible plasticity followed by a repeatable steady state with finite, velocity-independent hysteresis. Upon validating simulations by comparing bulk responses and spatial distribution of contact points with those of experiments, we trace the prominent bulk responses to their micromechanical origin in the motion of inter-element contact points