Fracture toughness of bone using a compact sandwich specimen: effects of sampling sites and crack orientations

The energy required to propagate a crack through bone can be estimated in terms of its fracture toughness, which is an intrinsic property and an important measure of the material's susceptibility to fracture. However, in the past detailed fracture toughness characterization of bone has been limited due to specimen size limitations. To address this issue the present study used a compact sandwich specimen and examined the variation in fracture toughness of bovine femoral bone as a function of testing sites and crack orientations. Two crack orientations, radial and circumferential, and three testing sites situated along the thickness of bone were investigated. The results indicated that there were statistically significant differences in fracture toughness between the testing sites for both radial and circumferencial cracks. Crack orientation also appeared to influence the fracture toughness at two of the test sites. The microstructure of bone and its fracture surface morphology were examined using microscopy and exhibited differences corresponding to the differences in fracture toughness, thus suggesting a correlation between microstructure and fracture toughness.