nacre: one construct, many systems

In biology, nacre (mother-of-pearl) is the iridescent inner layer of many mollusc shells, built as a brick-and-mortar stack of microscopic aragonite (calcium carbonate) platelets bonded by thin layers of protein and polysaccharide. Jackson, Vincent, and Turner's The mechanical design of nacre showed how this layered organic–mineral composite achieves toughness far beyond the brittle mineral alone, because the soft layers deflect cracks and let platelets slide. The referent is the structured biomineral tissue itself, the same material a jeweller calls mother-of-pearl and an engineer tries to copy.[1]

Unit

The toughness and strength of the layered aragonite–protein shell material

Recovery means

Not applicable

Measured by

Measured by fracture toughness, work of fracture, and bending strength, related to platelet size and the organic interlayer

In materials science, nacre is a design template: its brick-and-mortar geometry turns brittle ceramic tough by forcing cracks onto long, energy-sapping paths, so engineers build nacre-like composites that imitate the platelet-and-interlayer arrangement. Munch and colleagues' Tough, bio-inspired hybrid materials reproduced the architecture in alumina–polymer and alumina–metal composites and recovered much of nacre's toughness. The construct is the same structure–property relationship found in the shell, abstracted into an engineering principle.[2]

Unit

The toughness gained by reproducing nacre's layered architecture in a synthetic composite

Recovery means

Not applicable

Measured by

Quantified by fracture toughness and crack-growth resistance of the engineered composite versus its plain ceramic