Nanomechanics and ultrastructural studies of cortical bone : fundamental insights regarding structure-function, mineral-organic force mechanics interactions, and heterogeneity

Although the mechanics of bone has been studied extensively at the micro- and macro-scale, the nano-scopic level is perhaps the most illuminating as this is the length scale at which the individual constituents interact. Bone is made primarily up of type I collagen, hydroxyapatite mineral, a variety of non-collagenous proteins, and water. A multitechnique experimental and modeling approach methodology was used break down several of the deformation mechanisms that exist in bone at the nanoscale including the effect of mineral content, cohesive-frictional plasticity, increased ductility through mechanical heterogeneity, and intermolecular forces. To show that mineral content had a significant effect on both nanomechanical properties and ultrastructural deformation mechanisms of bone, partial and complete demineralization was carried out to produce samples ranging from -0-58 wt.% mineral content. Nanoindentation experiments perpendicular to the osteonal axis found a 4-6x increase in stiffness for the -58 wt.% sample compared to the completely demineralized -~0 wt.% samples. These results are discussed in the context of in situ and post-mortem AFM imaging studies which shed light on nanoscale mechanisms of deformation including collagen fibril deformation and pressure induced structural transitions of the mineral component.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Materials Science and Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2007

Author dc:creator

• Tai, Kuangshin

Advisor dc:contributor.advisor

• Christine Ortiz.

• Materials Science and Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/40351

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/40351