Multiscale Mechanics of Bone
Iwona Jasiuk, Department of Mechanical Science & Engineering, University of Illinois at Urbana – Champaign
Friday, Jan. 16, 2015
Bateman Physical Sciences Wing H (PSH) 153 [map]
Bone is a biological material with excellent material properties: high stiffness, strength and fracture toughness, and low weight. These superior properties of bone are due to its complex composite and hierarchical structure. In this presentation we summarize our results on the multiscale characterization and modeling of bone which provide structure-composition-properties relations. In the analysis, we distinguish the following length scales: nanoscale (few nanometers, apatite crystal and collagen fibril level), sub-microscale (few microns, single lamella level), microscale (10-500 microns single trabecula or osteon level), the mesoscale (1–10 cm, involving a random network of struts in trabecular bone, or a random arrangement of osteons in cortical bone), and macroscale (whole bone). We characterize the bone structure and composition using scanning and transmission electron microscopy, micro-computed tomography, spectroscopy and ash and water contents and measure properties of bone using nanoindentation, reference point indentation and tensile test. These experimental results are used as inputs for our theoretical models and for their validation. Our multiscale model involves a “bottom-up” approach in which the properties at lower level serve as inputs for modeling at the next structural level. Mechanical properties are determined at each scale either analytically, using micromechanics theories, or numerically, using finite element approaches. Computational challenges include modeling of the complex irregular structure at each structural level and accounting for a spatial heterogeneity of bone. Theoretical challenges include separation of scales and dependence of properties on specimen size and boundary conditions. Elastic constants and strength are calculated at each structural level and are compared with those measured experimentally. Results of this study have applications in orthopedics, including a more accurate assessment bone quality and earlier diagnosis of osteoporosis, and can guide design of bioinspired materials for a range of engineering applications.
Iwona Jasiuk received her Ph.D. in theoretical and applied mechanics at Northwestern University. Prior to joining the faculty of mechanical engineering at the University of Illinois at Urbana-Champaign (UIUC), she held academic positions at Michigan State University, Georgia Institute of Technology, and Concordia University. She also holds an affiliate faculty position in Bioengineering Department and part-time faculty positions at Institute for Genomic Biology and Beckman Institute at UIUC. Her research interests are in micromechanics of materials including composite materials, nanomaterials, and biological materials with a focus on bone. Her projects on bone include include multiscale mechanics of bone as a function of age and disease, bone adaptation, and bone tissue regeneration. She is a co-editor of the Journal of Mechanics of Materials and Structures and serves on editorial boards of the International Journal for Multiscale Computational Materials, International Journal of Damage Mechanics, Journal of Surfaces and Interfaces in Materials, and Frontiers in Biomechanics, among others. She is a Fellow of the American Society of Mechanical Engineers since 2003, a Fellow of the Society of Engineering Science since 2012, and in 2006 she served as president of the Society of Engineering Science.