Mechanical behavior of ultrastructural biocomposites

For numerous centuries nature has successfully developed biocomposite materials with detailed multiscale architectures to provide a material stiffness, strength and toughness. One such example is nacre, which is found in the shells of many mollusks, and consists of an inorganic phase of aragonite tablets 5-8jim in planar dimension and 0.5-1gm in thickness direction and an organic phase of biomacromolecules. High resolution microscopy imaging was employed to investigate the microscale features of seashell nacre to reveal the nucleation points within tablets, the sector boundaries and an overlap between tablets of neighboring layers of [approx.] 20 %. Aragonite, the mineral constituting the inorganic phase of nacre, is a calcium carbonate mineral that is ubiquitous in many natural systems, including both living organisms and geological structures. Resistance to yield is an important factor in the ability of aragonite to provide both strength and toughness to numerous biological materials. Conversely, plastic deformation of aragonite is a governing factor in the formation and flow of large scale geological structures. The technique of nanoindentation combined with in-situ tapping mode atomic force microscopy imaging was used to show the anisotropic nanoscale plastic behavior of single crystal aragonite for indentations into three mutually orthogonal planes.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Mechanical Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2006

Author dc:creator

• Kearney, Cathal (Cathal John)

Advisor dc:contributor.advisor

• Mary C. Boyce.

• Mechanical 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/1721.1/38269

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/38269