Mollusks have soft innards, but their complex exteriors protect them in harsh conditions. Engineers are beginning to understand how.
By modeling the average mollusk’s mobile habitat, they are learning how shells stand up to extraordinary pressures at the bottom of the sea. The goal is to learn what drove these tough exoskeletons to evolve as they did and to see how their mechanical principles may be adapted for use in human-scale structures like vehicles and even buildings.
The team led by Chandra Sekhar Tiwary, a graduate student at the Indian Institute of Science and a visiting student at Rice University, created computer simulations and printed 3D variants of two types of shells to run stress tests alongside real shells that Tiwary collected from beaches in India.
NACRE SHELLS
Shells are made of nacre, also known as mother-of-pearl, a strong and resilient matrix of organic and inorganic materials recently studied by other Rice engineers as a model of strength, stiffness, and toughness.
Tiwary and his colleagues took their research in a different direction to discover how seashells remain stable and redirect stress to minimize damage when failure is imminent. Their calculations showed their distinctive shapes make the shells nearly twice as good at bearing loads than nacre alone.
They examined two types of mollusk: bivalves with two separate exoskeleton components joined at a hinge (as in clamshells) and terebridae that conceal themselves in screw-shaped shells.
In the case of clamshells, the semicircular shape and curved ribs force stress to the hinge, while the screws direct the load toward the center and then the wide top.
They found such evolutionary optimization allows fractures to appear only where they’re least likely to hurt the animal inside.
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