Bone : technical material, rigid and tough.

Bone is a tissue with remarkable mechanical performance, combining high stiffness and high toughness. While its structure extends over seven or more levels of hierarchy, its basic building block, the mineralized collagen fibril, is rather universal. It consists of staggered arrays of collagen molecules reinforced by nanometer sized mineral platelets. The mineral is carbonated hydroxyapatite (dahlite) and its amount is usually thought to determine the stiffness of the material. However, the properties of the organic matrix and the geometrical arrangement of the organic and the mineral components at all levels of hierarchy determine the way in which the material deforms and fractures. The hierarchical structure is known to adapt to the biological function of the bone, and plays a critical role in controlling its susceptibility to fracture. An extended version of this review will be published in ...