| Abstract Scope |
The origins of the toughness of human cortical bone are examined in terms of the contributing micro-mechanisms and their characteristic length-scales in relation to its hierarchical structure. It is shown that at length-scales below a micron, toughening mechanisms in bone are primarily intrinsic, and include mechanisms such as collagen fibrillar sliding; these are essentially “plasticity” mechanisms. At length-scales above a micron, toughening mechanisms are primarily extrinsic, and associated with crack deflection and bridging. Here we evaluate the effects of aging, irradiation, vitamin-D deficiency and certain bone diseases, using in situ fracture-mechanics testing in an environmental scanning electron microscope combined with structure characterization using Raman spectroscopy, SAXS/WAXS and synchrotron x-ray computed microtomography, to determine the microstructural features that underlie the toughness of bone and how this can degrade with biological factors. |