Tensile experiments and SEM fractography on bovine subchondral bone

Subchondral bone undecalcified samples, extracted from bovine femoral heads , are subjected to a direct tensile load. The Young's modulus of each sampl e is determined from repeated tests within the elastic limit. In a last tes t, the tensile load is increased up to the specimen failure, determining th e ultimate tensile strength. The investigation is performed on both dry and wet specimens. The measured Young's modulus for dry samples is 10.3 +/- 2. 5 GPa, while that of wet samples is 3.5 +/- 1.2 GPa. The ultimate tensile s trengths are 36 +/- 10 and 30 +/- 7.5 MPa for dry and wet specimens, respec tively. SEM micrographs of failure surfaces show characteristic lamellar bo ne structures, with lamellae composed of calcified collagen fibers. Rudimen tary osteon-like structures are also observed, Failure surfaces of wet samp les show a marked fiber pull-out, while delamination predominates in dry sa mples. The obtained results are interpreted on the basis of the deformation mechanisms typical of fiber-reinforced laminated composite materials. (C) 2000 Elsevier Science Ltd. All rights reserved.