 |
| Spiralled layers are very good at dispersing forces. |
This mantis shrimp is famous for punching so hard (up to 1500 Nm) and closing its claw so fast (about 100km/h) that it momentarily separates air from water to create an air bubble that almost immediately implodes with a flash of light said to be as hot as the Sun’s surface.
High-speed boat screws create the same tiny, super-hot collapsing -- or cavitation -- air bubbles in water, which is why the metal edges of the boat screws quickly become as pitted as if they had been touched by hot welding rods.
In a study first published in Acta Biomaterialia, the California team asked why the mantis shrimp’s claw did not suffer damage when it punches with up to 1500 Newton metres of force?
The answer lies in how the claw is structured, and promises to lead to new materials that may one day be used to build cars and airplanes.
They found the structure of a shrimp’s claw dispersed the impact throughout the claw, allowing the material to withstand compression tests.
In previous studies, the team established that the claw’s covering, called cuticle, is made up of several layers, the innermost of which is the endocuticle. This is comprised of a spiralling arrangement of mineralised fibre layers, each of which is laid at a slightly rotated angle, forming a complete spiral and acting as a shock absorber.
The team formed a similar spiral using carbon fibre-epoxy composites. This spiral was made with the fibres set at three different angles ranging from 10 to 25° to the previous layer and compared to two control spirals — a simple one-way spiral and a spiral in which each layer was placed at a quarter turn to the previous one.
Weights were then dropped on the spirals to determine the strength and the damage caused. These were studied using ultrasound. The results showed the mantis shrimp material, while showing some damaged fibres, suffered 80% less damage.
