The fracture mechanics of bone—another look at composite modeling

Abstract

The energy absorbed in the impact fracture of bovine metatarsal and metacarpal bone was shown to depend on the aspect from which the inpact specimen was obtained. In a majority of cases caudad specimens were more than an order of magnitude tougher than cephalad specimens and the fracture surfaces of the tough specimens were fibrous or woody in appearance due to osteon pull out. This pull out phenomenon was identified as a major factor in determining the toughness of bone and is analogous to the toughening effect produced by fiber pull out in synthetic composites. Whenever a substantial component of the applied stress was resolved across the osteons, the fracture cracks were seen to propagate in an interosteonal mode similar to the delamination of synthetic composites with weak interfaces. Plastic deformation of the matrix is the third mechanism commonly employed to effect toughening in synthetic composites. Although no similar phenomenon was demonstrated in this study, it is probable that this also makes some contribution to the work‐to‐fracture of bone.