An examination of the micromechanics of failure of bone and antler by acoustic emission tests and Laser Scanning Confocal Microscopy

Abstract

Bone fails as a result of damage accumulation in the form of microcracks. Antler is in essence less mineralized bone, but is much tougher than ordinary bone. Failure through damage accumulation also happens in antler, so it is clear that antler's microcracks must be pervasive and that natural selection has produced mechanisms for this material which make it more damage-tolerant. We have examined the development of damage in bone and antler by cyclic loading in three-point bending. We have also conducted acoustic emission studies on these two materials during monotonic tensile loading, and used Laser Scanning Confocal Microscopy (LSCM) to observe microcracks in samples which had been mechanically damaged. We found that diffuse microcracking coincides with the appearance of a macroscopic region of 'yield' in the stress/strain curve of bone and antler; it is related to the local stress (or strain) field that microcracks interact with the structure (particularly in antler). Both acoustic emissions studies and LSCM observations indicated that antler may possess additional modes of stable micromechanical failure compared with ordinary bone.