title: In situ micropillar compression reveals superior strength and ductility but an absence of damage in lamellar bone.
abstract: Ageing societies suffer from an increasing incidence of bone fractures. Bone strength depends on the amount of mineral measured by clinical densitometry, but also on the micromechanical properties of the hierarchical organization of bone. Here, we investigate the mechanical response under monotonic and cyclic compression of both single osteonal lamellae and macroscopic samples containing numerous osteons. Micropillar compression tests in a scanning electron microscope, microindentation and macroscopic compression tests were performed on dry ovine bone to identify the elastic modulus, yield stress, plastic deformation, damage accumulation and failure mechanisms. We found that isolated lamellae exhibit a plastic behaviour, with higher yield stress and ductility but no damage. In agreement with a proposed rheological model, these experiments illustrate a transition from a ductile mechanical behaviour of bone at the microscale to a quasi-brittle response driven by the growth of cracks along interfaces or in the vicinity of pores at the macroscale.
authors.affiliation: Institute for Surgical Technology and Biomechanics, University of Bern, Stauffacherstr. 78 CH-3014 Bern, Switzerland.
authors.forename: Jakob
authors.initials: J
authors.lastname: Schwiedrzik
authors.affiliation: 1] EMPA, Swiss Federal Laboratories for Material Science and Technology, Laboratory of Mechanics of Materials and Nanostructures, Feuerwerkerstr. 39, CH-3602 Thun, Switzerland [2].
authors.forename: Rejin
authors.initials: R
authors.lastname: Raghavan
authors.affiliation: Institute for Surgical Technology and Biomechanics, University of Bern, Stauffacherstr. 78 CH-3014 Bern, Switzerland.
authors.forename: Alexander
authors.initials: A
authors.lastname: Bürki
authors.affiliation: EMPA, Swiss Federal Laboratories for Material Science and Technology, Laboratory of Mechanics of Materials and Nanostructures, Feuerwerkerstr. 39, CH-3602 Thun, Switzerland.
authors.forename: Victor
authors.initials: V
authors.lastname: LeNader
authors.affiliation: Institute for Surgical Technology and Biomechanics, University of Bern, Stauffacherstr. 78 CH-3014 Bern, Switzerland.
authors.forename: Uwe
authors.initials: U
authors.lastname: Wolfram
authors.affiliation: 1] EMPA, Swiss Federal Laboratories for Material Science and Technology, Laboratory of Mechanics of Materials and Nanostructures, Feuerwerkerstr. 39, CH-3602 Thun, Switzerland [2].
authors.forename: Johann
authors.initials: J
authors.lastname: Michler
authors.affiliation: 1] Institute for Surgical Technology and Biomechanics, University of Bern, Stauffacherstr. 78 CH-3014 Bern, Switzerland [2].
authors.forename: Philippe
authors.initials: P
authors.lastname: Zysset
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D001842:Bone and Bones / Q000502:physiology* / Q000648:ultrastructure; D019245:Compressive Strength; D008855:Microscopy, Electron, Scanning; D012756:Sheep / Q000033:anatomy & histology / Q000502:physiology; D013314:Stress, Mechanical