Fiber networks below the isostatic point: Fracture without stress concentration

Abstract

Crack nucleation, in which a crack is propagated via the concentration of stress at its tip, is a ubiquitous phenomenon. Here, we show via simulations and theory that in systems such as fiber networks that are below the point of mechanical stability, continuous nonlinear alignments lead to a steady state in which new load-bearing fiber chains emerge to replace those lost to fracture, preventing stress concentration and leading to the accumulation of distributed damage over a divergent length scale. In contrast to linear models that display diverging length scales at a critical point, this phenomenon occurs over a large parameter range, and is expected to be observed in biopolymer networks and porous artificial materials. This mixture of fiber alignment and fracture leads to massively greater energy dissipation and to fracture avalanche statistics distinct from those present in linear models.