Nonlinear elasticity of semiflexible filament networks

TL;DR

This paper presents a continuum theory for the nonlinear elasticity of semiflexible filament networks, accurately modeling their stress-strain behavior and the Poynting effect across different filament stiffnesses.

Contribution

It introduces a 3-chain constitutive model for semiflexible networks, deriving analytical energy expressions and fitting experimental data with only two parameters.

Findings

The theory matches experimental shear data across various filament networks.

It captures the transition from positive to negative Poynting effect with filament stiffness.

Analytical expressions enable prediction of network response under different strains.

Abstract

We develop a continuum theory for equilibrium elasticity of a network of crosslinked semiflexible filaments, spanning the full range between flexible entropy-driven chains to stiff athermal rods. We choose the 3-chain constitutive model over several plausible candidates, and derive analytical expressions for the elastic energy at arbitrary strain, with the corresponding stress-strain relationship. The theory fits well to a wide range of experimental data on simple shear in different filament networks, quantitatively matching the differential shear modulus variation with stress, with only two adjustable parameters (which represent the filament stiffness and pre-tension in the network, respectively). The general theory accurately describes the crossover between the positive and negative Poynting effect (normal stress on imposed shear) on increasing the stiffness of filaments forming the network.