Macromolecular structure of the organic framework of nacre in Haliotis rufescens: implications for mechanical response.

Direct experimental probes of the mechanical response of the biopolymer framework of nacre extracted from the shell of the gastropod Haliotis rufescens have been performed. Both monotonic tensile, and time dependent relaxation, tests revealed that the tissue comprising the interlamellar layers within nacre obeyed a simple constitutive model conforming to the visco-elastic standard linear solid, with time constants in the range tau=140+/-4s. We conclude that the behavior is essentially that imparted by the chitin core of these layers. Interestingly we find that the chitin network of the core appears to be connected over multiple CaCO(3) tiles. A simple composite model is formulated and used to interpret the observed behavior.