Connectivity and plasticity determine collagen network fracture

Collagen fibers are the main components of the extracellular matrix, a fibrous scaffold that sets the shape and stiffness of tissues in the human body and protects them from mechanical failure. The relation between the hierarchical and heterogeneous structure of collagen networks and their fracture behavior is still missing. Prior studies focused on tendons, where collagen forms highly aligned bundles, but many tissues such as skin contain disordered collagen networks. Here, we show that fracture of disordered collagen networks is controlled by their connectivity rather than by the single-fiber properties. We further show that structural plasticity can delay network failure. Our findings are useful in understanding how tissues fail and in the design of stronger network-based materials.