Nonlinear mechanics of composite fiber networks

Fibrous networks such as collagen are ubiquitous in biological systems. Although the mechanical behavior of single fiber networks has been, both experimentally and theoretically, well studied, understanding the effect of the interplay between different biopolymer networks remains unclear especially under large deformations. In this work, we model a rigid fiber network inside a soft and flexible underlying matrix. This double network model enables us to study the effect of internal interactions of different networks on their overall mechanics. We find that the linear shear modulus of the composite system is greater than the sum of the individual linear shear moduli. Moreover, by calculating the non-affine fluctuations, we see clear suppression of fluctuations in the rigid fiber network. We also find a mechanical phase transition between matrix-dominated and fiber-dominated states.