title: Natural stiffening increases flaw tolerance of biological fibers.
abstract: Many fibers in biomaterials such as tendon, elastin, or silk feature a nonlinear stiffening behavior of the stress-strain relationship, where the rigidity of the material increases severely as the material is being stretched. Here we show that such nonlinear stiffening is beneficial for a fiber's ability to withstand cracks, leading to a flaw tolerant state in which stress concentrations around cracks are diminished. Our findings, established by molecular mechanics and the derivation of a theoretical scaling law, explain experimentally observed fiber sizes in a range of biomaterials and point to the importance of nonlinear stiffening to enhance their fracture properties. Our study suggests that nonlinear stiffening provides a mechanism by which nanoscale mechanical properties can be scaled up, providing a means towards bioinspired fibrous material and structural design.
authors.affiliation: Laboratory for Atomistic and Molecular Mechanics, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Room 1-235A&B, Cambridge, Massachusetts 02139, USA.
authors.forename: Tristan
authors.initials: T
authors.lastname: Giesa
authors.forename: Nicola M
authors.initials: NM
authors.lastname: Pugno
authors.forename: Markus J
authors.initials: MJ
authors.lastname: Buehler
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry*; D001703:Biophysics / Q000379:methods; D003094:Collagen / Q000737:chemistry; D055119:Elastic Modulus; D004548:Elasticity; D004549:Elastin / Q000737:chemistry; D005349:Fibroins / Q000737:chemistry; D008422:Materials Testing; D015233:Models, Statistical; D008962:Models, Theoretical; D011108:Polymers / Q000737:chemistry*; D012044:Regression Analysis; D047011:Silk / Q000737:chemistry*; D013314:Stress, Mechanical; D013710:Tendons / Q000737:chemistry; D013718:Tensile Strength
chemical_list: D001672:Biocompatible Materials; D011108:Polymers; D047011:Silk; D003094:Collagen; D004549:Elastin; D005349:Fibroins