Inspiration for the design of new lightweight armours could be drawn from the hierarchical structure and deformation properties of a bivalve mollusc shell, reports a study published online this week in Nature Materials.

Ling Li and Christine Ortiz probed the penetration resistance and deformation mechanisms of the bivalve Placuna placenta following the application of nanoscale indentations to its shell. They find that the shell is able to localize the damage by deforming to give nanoscale twins - thin, crystalline twins of calcite with an atomic arrangement that is mirrored across the twin boundary. The formation of these twins confines the deformation to a small volume and also causes other inelastic energy dissipating events including nanocracking within and between the calcite crystals, crack deflection and stretching of the organic material between the crystals.

The deformation mechanisms revealed in this work could, in theory, be applied in the development of materials for military and personal protection applications.