Nacre (mother-of-pearl) achieves extraordinary toughness for a mostly brittle mineral by stacking hard platelets with a thin, energy-absorbing organic layer between them that deflects cracks instead of letting them run straight through.
toughness_composite >> toughness_mineral (crack deflection at brick-mortar interfaces)
- Layer segments — the number of hard-platelet 'brick' layers stacked in the composite, mimicking nacre's structure.
- Mortar toughness — how effectively the soft biopolymer 'mortar' between platelets deflects and arrests cracks.
- Applied load — the mechanical force the composite panel must withstand without fracturing.
- Load cycling speed — how fast the load is applied/moved, testing fatigue resistance as well as static strength.
Engineers have used nacre's brick-and-mortar principle to design impact-resistant ceramics, aircraft panels and even phone-screen coatings, achieving toughness far beyond what the brittle mineral component could manage alone.