Fracture Mechanics of Cortical Bone

Abstract

Cortical bone is notch sensitive and the presence of surface cracks significantly reduces the energy absorbed during fracture for both longitudinal and transverse fracture directions [1]. A variety of fracture mechanics techniques have been utilized to assess the fracture toughness of bone specimens with a “characterized” crack, which have included measurements of the critical strain energy release rate (G_C) (or the specific surface energy γ, = G_C/2), and the critical stress intensity factor, K_C [2–5]. The specimen geometries used in the earlier experiments all produced rapid crack propagation, with an unknown and variable crack velocity. More recently, in contrast, with the use of the compact tension method [6], it has been possible to propagate a crack in bone at a relatively slow and measurable rate and G_C and K_C values for transversely oriented bovine femur and tibia bone specimens were determined by this method for various crack velocities [7–8]. The results of these investigations are shown for comparison in Table 1.