title: Extracellular bone matrix exhibits hardening elastoplasticity and more than double cortical strength: Evidence from homogeneous compression of non-tapered single micron-sized pillars welded to a rigid substrate.
abstract: We here report an improved experimental technique for the determination of Young׳s modulus and uniaxial strength of extracellular bone matrix at the single micrometer scale, giving direct access to the (homogeneous) deformation (or strain) states of the tested samples and to the corresponding mechanically recoverable energy, called potential or elastic energy. Therefore, a new protocol for Focused Ion Beam milling of prismatic non-tapered micropillars, and attaching them to a rigid substrate, was developed. Uniaxial strength turns out as at least twice that measured macroscopically, and respective ultimate stresses are preceded by hardening elastoplastic states, already at very low load levels. The unloading portion of quasi-static load-displacement curves revealed Young׳s modulus of 29GPa in bovine extracellular bone matrix. This value is impressively confirmed by the corresponding prediction of a multiscale mechanics model for bone, which has been comprehensively validated at various other observation scales, across tissues from the entire vertebrate animal kingdom.
authors.affiliation: Institute for Mechanics of Materials and Structures, Vienna University of Technology (TU Wien), Karlsplatz 13/202, 1040 Vienna, Austria.
authors.forename: Krzysztof W
authors.initials: KW
authors.lastname: Luczynski
authors.affiliation: University Service Center for Transmission Electron Microscopy, Vienna University of Technology (TU Wien), Wiedner Hauptstrasse 8-10, 1040 Vienna, Austria.
authors.forename: Andreas
authors.initials: A
authors.lastname: Steiger-Thirsfeld
authors.affiliation: University Service Center for Transmission Electron Microscopy, Vienna University of Technology (TU Wien), Wiedner Hauptstrasse 8-10, 1040 Vienna, Austria.
authors.forename: Johannes
authors.initials: J
authors.lastname: Bernardi
authors.affiliation: Institute for Mechanics of Materials and Structures, Vienna University of Technology (TU Wien), Karlsplatz 13/202, 1040 Vienna, Austria.
authors.forename: Josef
authors.initials: J
authors.lastname: Eberhardsteiner
authors.affiliation: Institute for Mechanics of Materials and Structures, Vienna University of Technology (TU Wien), Karlsplatz 13/202, 1040 Vienna, Austria. Electronic address: christian.hellmich@tuwien.ac.at.
authors.forename: Christian
authors.initials: C
authors.lastname: Hellmich
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D002417:Cattle; D019245:Compressive Strength; D055119:Elastic Modulus; D005109:Extracellular Matrix / Q000378:metabolism*; D005269:Femur / Q000166:cytology*; D008422:Materials Testing / Q000295:instrumentation*; D013314:Stress, Mechanical
keywords: Bone; Elastoplasticity; Focused ion beam milling; Homogeneous strain state; Micropillars; Unloading