Mighty molluscs with transparent shells could help protect soldiers in battle. Analysis of oyster shells shows how they can take repeated beatings without shattering, perhaps inspiring tougher combat armour.
Current transparent shields and visors are made from laminated glass, which fractures if it takes a bullet. That makes it hard to see through and vulnerable to breaking with a second hit, says at the Massachusetts Institute of Technology. 鈥淩ight now, once they鈥檙e shot, that鈥檚 it,鈥� she says. 鈥淪o any sort of transparent armour that has multi-hit capability but can also stop penetrations would be of interest.鈥�
Video: Mollusc shells take a beating without shattering
In nature, many creatures use transparent shells for camouflage, which can survive repeated attacks from predators. 鈥淚f you just hit the shell and it fell apart, the whole animal would be dead,鈥� says Ortiz.
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So Ortiz and her team studied the nanoscale structure of shells of the windowpane oyster, which are made of 99 per cent calcite mineral. Pure calcite crystals shatter easily, but the oyster shell is organised in thin layers that shift orientation when stressed, confining damage to shallow craters and stopping fractures spreading (see picture).
While natural shells would not stop a bullet, finding a way to create such nano-layers in military-grade ceramics could one day help build better transparent shields, says Ortiz.
鈥淭his work is fascinating, but the real punch line is if you could actually make a material,鈥� says at Lawrence Berkeley National Laboratory in California, whose team made a material based on mother-of-pearl in 2008.
Constructing such materials with ceramics is challenging, because right now the temperatures needed to harden the ceramics will destroy the polymers used to slide in between them and create layers. 鈥淚t鈥檚 feasible, but it will be very difficult.鈥�
Journal reference: Nature Materials, DOI: 10.1038/nmat3920
