Elasticity of fibrous networks under axial prestress

TL;DR

This study combines theoretical modeling and experiments to understand how uniaxial strain affects the nonlinear elastic behavior of fibrous networks like fibrin and collagen, emphasizing the roles of boundary conditions and strain in network mechanics.

Contribution

It provides a combined experimental and computational analysis revealing how axial prestress influences fibrous network elasticity, clarifying the origin of softening and stiffening behaviors.

Findings

Uniaxial strain induces nonlinear stiffening or softening in fibrous networks.

Boundary conditions significantly affect the onset of stiffening.

Computational models replicate experimental nonlinear responses.

Abstract

We present theoretical and experimental studies of the elastic response of fibrous networks subjected to uniaxial strain. Uniaxial compression or extension is applied to extracellular networks of fibrin and collagen using a shear rheometer with free water in/outflow. Both axial stress and the network shear modulus are measured. Prior work [van Oosten et al., Scientific Reports, 2015, 6, 19270] has shown softening/stiffening of these networks under compression/extension, together with a nonlinear response to shear, but the origin of such behaviour remains poorly understood. Here, we study how uniaxial strain influences the nonlinear mechanics of fibrous networks. Using a computational network model with bendable and stretchable fibres, we show that the softening/stiffening behaviour can be understood for fixed lateral boundaries in 2D and 3D networks with comparable average connectivities to the experimental extracellular networks. Moreover, we show that the onset of stiffening depends strongly on the imposed uniaxial strain. Our study highlights the importance of both axial strain and boundary conditions in determining the mechanical response of hydrogels.