Osteon Size Effect on the Dynamic Fracture Toughness of Bone

Bone is a highly studied material due to its complex microstructure and its ability to withstand fracture. It is a strong and lightweight material that has strengthening mechanisms that would be ideal if replicated in composite materials. At quasi-static loading it has been shown to have several strengthening mechanisms. One of the main proponents against fracture in the transverse direction (perpendicular to the loading axis) is crack deflection

[1]

. Cortical bone, which is comprised of tube-like structures called osteons, is able to deflect a propagating crack up to 90°

[4]

which can reduce the driving force for crack advance up to 50% when compared to the undeflected crack

[3]

. It does this by rerouting the crack along the weaker cement lines that are present along the outside of osteons. It has also been shown that the size and orientation of osteons have an influence on mechanical properties

[1]

. Smaller osteons increase the tensile fracture toughness

[2]

but due to bone’s anisotropic nature, it is unclear if this relation holds true under dynamic loading. Bone loaded at strain rates greater than 1s

-1

will yield different results when compared to static loading

[5]

. This study aims to determine which size and density of osteons will yield the greatest resistance to fracture at dynamic loading.