From brittle to ductile fracture of bone

Nat Mater. 2006 Jan;5(1):52-5. doi: 10.1038/nmat1545. Epub 2005 Dec 11.


Toughness is crucial to the structural function of bone. Usually, the toughness of a material is not just determined by its composition, but by the ability of its microstructure to dissipate deformation energy without propagation of the crack. Polymers are often able to dissipate energy by viscoplastic flow or the formation of non-connected microcracks. In ceramics, well-known toughening mechanisms are based on crack ligament bridging and crack deflection. Interestingly, all these phenomena were identified in bone, which is a composite of a fibrous polymer (collagen) and ceramic nanoparticles (carbonated hydroxyapatite). Here, we use controlled crack-extension experiments to explain the influence of fibre orientation on steering the various toughening mechanisms. We find that the fracture energy changes by two orders of magnitude depending on the collagen orientation, and the angle between collagen and crack propagation direction is decisive in switching between different toughening mechanisms.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bone and Bones / chemistry*
  • Bone and Bones / physiology
  • Collagen / chemistry*
  • Collagen / ultrastructure
  • Durapatite / chemistry*
  • Fractures, Bone*
  • Hardness Tests
  • Nanostructures / chemistry*
  • Nanostructures / ultrastructure
  • Stress, Mechanical


  • Collagen
  • Durapatite