Elastic anisotropy of uniaxial mineralized collagen fibers measured using two-directional indentation. Effects of hydration state and indentation depth.
Mineralized turkey leg tendon (MTLT) is an attractive model of mineralized collagen fibers, which are also present in bone. Its longitudinal structure is advantageous for the relative simplicity in modeling, yet its anisotropic elastic properties remain unknown. The aim of this study was to quantify the extent of elastic anisotropy of mineralized collagen fibers by using nano- and microindentation to probe a number on MTLT samples in two orthogonal directions. The large dataset allowed the quantification of the extent of anisotropy, depending on the final indentation depth and on the hydration state of the sample. Anisotropy was observed to increase with the sample re-hydration process. Artifacts of indentation in a transverse direction to the main axis of the mineralized tendons in re-hydrated condition were observed. The indentation size effect, that is, the increase of the measured elastic properties with decreasing sampling volume, reported previously on variety of materials, was also observed in MTLT. Indentation work was quantified for both directions of indentation in dried and re-hydrated conditions. As hypothesized, MTLT showed a higher extent of anisotropy compared to cortical and trabecular bone, presumably due to the alignment of mineralized collagen fibers in this tissue.
Institute of Lightweight Design and Structural Biomechanics, Vienna University of Technology, Gusshausstrasse 27-29, A-1040 Vienna, Austria.
Ewa M
EM
Spiesz
Paul
P
Roschger
Philippe K
PK
Zysset
D000818:Animals; D016880:Anisotropy; D001672:Biocompatible Materials / Q000737:chemistry; D001696:Biomechanical Phenomena; D001842:Bone and Bones / Q000378:metabolism; D003094:Collagen / Q000737:chemistry*; D004548:Elasticity; D008422:Materials Testing; D015233:Models, Statistical; D008962:Models, Theoretical; D010969:Plastics; D013710:Tendons / Q000473:pathology / Q000502:physiology; D014422:Turkeys; D014867:Water / Q000737:chemistry*
D001672:Biocompatible Materials; D010969:Plastics; D014867:Water; D003094:Collagen