Research and innovation have been part of the human experience since humanity began walking the earth. We are always looking for better materials to build the things we want. Our scientists and engineers are constantly looking for ways to make even the best materials stronger and more durable. In the search to do better, sometimes nature holds the key to secrets we are trying to unlock.
Nature contributes a lot to our understanding of composite materials. For example, consider the humble mantis shrimp and its deadly dactyl club used to kill prey and provide self-defense. Researchers from Purdue University and the University of California, Riverside began looking at the dactyl club in 2017 to try to better understand its strength and resilience. What they discovered has wide-reaching implications for the composites industry.
Small but Fierce
The mantis shrimp is a marine crustacean known for its fierceness and power. A typical mantis shrimp is only about 4 inches long, but it is definitely not to be messed with. The mantis shrimp is so tough that it has earned an array of interesting nicknames over the years, including:
- Sea Locust – Ancient Assyrians referred to the mantis shrimp as a sea locust because of its propensity to wreak widespread destruction of other species.
- Prawn Killer – The prawn killer name is commonly known in Australia. Mantis shrimp are known to be merciless toward many other species, including the beloved prawn.
- Thumb Splitter – On the more recent nicknames given to this fierce undersea creature is thumb splitter, a name relating to its ability to inflict painful and severe wounds when not handled with great care.
There is no doubt that the mantis shrimp and its dactyl club deserve to be taken seriously. But what does this have to do with composites? The secret of the creature’s defense lies in the architecture of the dactyl club itself.
Strength in a Helicoid
The exoskeleton of the mantis shrimp consists of calcium carbonate and calcium phosphate, according to a Physics World article published earlier in 2018. Normally considered brittle, the natural exoskeleton material holds up extremely well in the mantis shrimp’s dactyl club due to the club’s natural helicoidal structure.
As the club is ‘built’ around a helicoidal core of chitin, all of the shock it absorbs is easily dispersed across its entire area. Researchers discovered that micro-cracks form within the interior of the club during use but, because of the helicoidal architecture, they disperse energy and prevent total failure.
Utah-based Rock West Composites says that a number of industry studies have utilized the same helicoidal design to test its strength. The resulting materials have proved “much tougher than the traditional quasi-isotropic composite geometry in which the directionality of fibers is shifted… between layers,” reports Physics World.
Resistance to Failure Is Key
One of the most important lessons learned from the Purdue University and UC Riverside research is that resistance to failure is key. It is okay for composites to endure some measure of stress as long as they do not fail completely.
In the case of the mantis shrimp, it is perfectly fine to have micro-cracks within the structure of the dactyl club because those cracks help disperse energy. Just as long as they don’t become major cracks that actually split the club, they serve a very important purpose of preventing failure.
Nature can teach us a lot about how to make better, stronger composite materials. Thanks to what we have learned about the mantis shrimp, we now have a better understanding of how to use helicoidal architecture to our advantage.