Structure/mechanical behavior relationships in crossed-lamellar sea shells

Common sea shells are composed by layers of CaCO3, sandwiched between biopolymers. This structure provides strength, hardness and toughness (e.g. nacre is 3000 times as tough as its constituent phases), and has inspired the development of high performance nanocomposites. Micro-mechanics experiments have shown that the organic phase between the ceramic plates, despite its low volume content, plays an important role in the fracture resistance of the marine shell structures.

This study aims at investigating the influence of the adhesive organic phase upon the macroscopic mechanical properties in a sea shell (Solen marginatus). In this work the mechanical properties of those systems are measured in different conditions: wet state; dry state and with the organic phase removed. A clear crossed-lamellar morphology was observed in the fresh shell. The drying (loss of water) did not influence the microstructure but caused a substantial decrease in stiffness. The extraction of the organic phase by calcination changed severely the microstructure and decrease significantly the strength and the work of fracture of the specimens.