Eur. Phys. J. E 4, 121-127

Why is nacre strong? Elastic theory and fracture mechanics for biocomposites with stratified structures

K. Okumura^1,2 and P.-G. de Gennes¹.

¹  Physique de la Matière Condensée, Collège de France, 11, place Marcelin-Berthelot, 75231 Paris cedex 05, France
²  Theoretical Studies, Institute for Molecular Science, Okazaki, Aichi 444-8585, Japan

okumura@phys.ocha.ac.jp

(Received 18 March 2000)

Abstract
Nacre, stratified ceramic layers surrounded by organic matrix, is a tough material found inside certain seashells. We construct a coarse-grained elastic energy for such an anisotropic system and present an analytic solution for a notch crack normal to the stratified sheets. This analysis proves the reduction in stress concentration which was announced in our earlier work (P. G. de Gennes and K. Okumura, C. R. Acad. Sci. Paris 1, Ser. IV, 257 (2000)) and the related increase in toughness.

PACS
87.68.+z - Biomaterials and biological interfaces.
46.50.+a - Fracture mechanics, fatigue and cracks.
83.70.Dk - Composite solids.


© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2001