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Andrew J. Rapoff with the University of Florida |
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Date: April 29, 2003
Time: 10:30am
Location: NASA LaRC, Bldg 1192C, Rm 102
Speaker: Andrew J. Rapoff with the University of Florida
Subject:* "Biomimetic Designs from Bone"
Additional Information: Presentation (PDF)
Our investigations of a natural hole in bone – the nutrient foramen – have resulted in an understanding of its enhanced structural performance under static and cyclic loading. The description of this investigative journey begins by recounting our discovery of a surprising spatial variation in material composition near the foramen that drives the stress concentration away from the edge and into a region of increased strength and toughness. Next explained is the transference of this knowledge into optimal designs of inhomogeneous plates containing holes for a class of materials, including bone, whose stiffness and strength have similar functional relationships with composition. Illustrated then is the fabrication and mechanical testing of plates that validated our understanding and design methods. Finally described is the quantification of the increased toughness of the foramen in cyclic loading experiments that matched it against a drilled hole subjected to the same mechanical duress. In summary, we have found compositional variations near the foramen that are optimized for decreased weight and increased structural performance. The biological underpinnings are not entirely clear but may be related to the need for minimizing the metabolic costs associated with carrying about the skeleton.
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