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)
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