Jun 28, 2018 | By Thomas

When looking for ways to strengthen a material, nature often provides the best answers. Researchers at Purdue University have used the mantis shrimp as inspiration - two years ago, they published research covering their use of 3D printing to develop new ultra-strong materials inspired by the rainbow-colored mantis shrimp. In their recent work, the researchers, in collaboration with University of California, Riverside, studied the mechanism behind just how mantis shrimp wields its powerful club without permanently damaging itself, and the design strategy, aiming to develop a new class of super-tough materials.

What makes the mantis shrimp stand out is that it can actually smash and defeat its armored preys (mostly mollusks and other crabs), which are also known for their damage-tolerance and excellent mechanical properties. The amazing sea creature has some incredible power behind its fists and can punch as fast as the 22-caliber bullet.

The mantis shrimp conquers its prey with a "dactyl club" appendage, which is made up of a composite material that grows tougher as cracks twist. (Purdue University image/Pablo Zavattieri)

New findings show that the composite material of the club actually becomes tougher as a crack tries to twist, in effect halting its progress. This crack twisting is guided by the material's fibers of chitin, the same substance found in many marine crustacean shells and insect exoskeletons, arranged in a helicoidal architecture that resembles a spiral staircase.

"This mechanism has never been studied in detail before," Zavattieri said. "What we are finding is that as a crack twists the driving force to grow the crack progressively decreases, promoting the formation of other similar mechanisms, which prevent the material from falling apart catastrophically. I think we can finally explain why the material is so tough.

“The novelty of this work is that, on the theory side, we developed a new model, and on the experimental side we used established materials to create composites that validate this theory.”

Purdue doctoral student Nobphadon Suksangpanya; UC Riverside doctoral student Nicholas A. Yaraghi; David Kisailus, a UC Riverside professor of chemical and environmental engineering and materials science and engineering; and Zavattieri published two papers in the Journal of the Mechanical Behavior of Biomedical Materials and the International Journal of Solids and Structures on their fascinating work.

The helicoidal architecture of a mantis shrimp's dactyl club is naturally designed to survive repeated high-velocity blows. (University of California, Riverside, Scanning Electron Microscope image/David Kisailus)

“This exciting new analytical, computational and experimental work, which follows up on our initial biocomposite characterization of the helicoid within the mantis shrimp’s club and biomimetic composite work, really provides a deeper insight to the mechanisms of toughening within this unique structure,” Kisailus said.

Previous research found that the dactyl club’s helicoidal architecture was naturally designed to survive the repeated high-velocity blows. In the new research, the team has learned specifically why this pattern imparts such toughness: as cracks form, they follow the twisting pattern rather than spreading straight across the structure, causing it to fail. New images taken with an electron microscope at UC Riverside show that instead of a single crack continuing to propagate, numerous smaller cracks form – dissipating the energy absorbed by the material upon impact.

The researchers created and tested 3D printed composites modeled after this behavior, capturing the crack behavior with cameras and digital image correlation techniques to study the deformation of the material.

Researchers have modeled 3D-printed composites after the twisting cracks responsible for the strength of the mantis shrimp's dactyl club. (Purdue University image/Pablo Zavattieri)

Zavattieri said, “We are establishing new mechanisms that were not available to us before for composites. Traditionally, when we produce composites we put fibers together in ways that are not optimal, and nature is teaching us how we should do it.”

The findings can help in developing lighter, stronger and tougher materials for many applications including aerospace, automotive and sports.

 

 

Posted in 3D Printing Application

 

Source: Purdue University

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