| Abstract: | Biopolymer fibrous network materials, such as skin and collagen-based connective tissues, are initially soft and compliant, but stiffen dramatically under mechanical strain. This generic phenomenon – termed the strain-stiffening phase transition – has important biological functions such as damage self-protection and poses basic challenges from the perspective of driven critical phenomena. We develop a comprehensive theory of the athermal strain-stiffening transition, obtaining all scaling exponents – at criticality and away from it – in terms of the small bending-to-stretching ratio of individual polymer fibers and the applied strain. By performing large-scale computer simulations, we demonstrate quantitative agreement between numerical results and all the analytic predictions. Finally, the universality of the strain-stiffening transition with respect to shear and volumetric strains is established. |