May 29, 2017 | By Benedict

Researchers at MIT have taken a close look at conch shells to discover how they are so resistant to impact, recreating the complex organic structures using a 3D printer. The researchers say that artificial conch-like structures could be used to create stronger helmets and body armor.

Mahdi Takaffoli (left) and Grace Gu (right) compare a real conch with their 3D printed version

When Ralph first blows into the conch in William Golding’s 1954 novel Lord of the Flies, the spiral-shaped shell seems to command an authority of its own: its deep sound instills a temporary discipline into the gang of castaway schoolchildren; its singularity makes Ralph the de facto leader of the group.

In real life, conch shells are remarkable for a simpler reason: their unusual structure makes them unbelievably strong—10 times tougher than mother of pearl, in fact.

So intriguing is the strength of the conch, it was recently the subject of an MIT study.

In this study, graduate student Grace Gu, postdoc Mahdi Takaffoli, and McAfee Professor of Engineering Markus Buehler attempted to better understand the secrets of the unusual shell. Their work, which explored how conches are so strong (and how that strength can be replicated), has been published in the journal Advanced Materials.

Upon getting a conch under the microscope, the researchers noted that the shell has a three-tiered structure that makes it very hard for cracks to spread and enlarge. The material of the shell has what Gu describes as a “zigzag matrix, so the crack has to go through a kind of a maze” in order to spread.

Ralph's posession of the conch makes him leader in William Golding's Lord of the Flies

Understanding the conch in this way is pretty exciting in itself, but the MIT researchers went a step further, using 3D printing technology to recreate the architecture of the shell.

Doing so allowed the researchers to perform advanced impact tests, in addition to static and virtual tests, on the conch architecture.

And although these 3D printed shell-like structures weren’t the real thing—in fact, their flat shape doesn't resemble a shell at all—the researchers believe the experiments were more useful than equivalent testing on real conches would have been. This is because conch shells have unpredictable variations within them, making them unsuitable for controlled experiments.

To test the importance of the three “levels” of a conch, the MIT researchers tried comparing their 3D printed conch structure with simpler, un-layered structures. By using a “drop tower,” an apparatus that drops a heavy weight on an object with a controlled and consistent force, the MIT experts could test the comparitive strength of the different materials.

Unsurprisingly, the multi-layered 3D printed conch structures won out.

“The results show that adding the second level of cross-lamellar hierarchy [as found in a conch] can boost impact performance by 70% and 85% compared to a single-level hierarchy and the stiff constituent, respectively,” the researchers wrote in their paper.

They were also able to incorporate “exactly the same geometry” into the 3D printed test materials as was used in their computer simulations, a move which purportedly produced “very good agreement” between the physical and virtual testing.

Testing found that the conch-like material architecture (below, right) was much stronger than other configurations

The results, despite being great news for the MIT researchers, do make you wonder whether Golding did his research properly. After all, his famous novel describes how the conch “exploded into a thousand white fragments” upon striking a rock.

Back to the matter at hand, and perhaps the best thing about this artificial conch-like material is that it is both strong (it resists damage) and tough (it dissipates energy, like rubber). The researchers say this makes the multi-layered structures suitable for incorporation into protective devices like helmets and body armor.

The 3D printing process used to create the conch-like materials means it would be possible to produce personalized, custom-fit items of this sort—a practice that is becoming more and more common. Earlier today we saw how sportswear company Riddell is using 3D scanning to improve its football helmets. Perhaps they could incorporate conch-like structures into their next models!

Gu says helmets equipped with the conch structures could be “tailored and personalized; the computer would optimize it for you, based on a scan of your skull, and the helmet would be printed just for you.”

So far, however, the researchers have only tested flat sections of the multi-layered conch structure, so they would have to conduct further experiments on curved shapes before implementing the design into helmets and other devices.

So there you have it: a 3D printed conch might not be able to instill discipline into a group of shipwrecked schoolchildren; it could, however, be the foundation of a new generation of helmets and body armor.

 

 

Posted in 3D Printing Application

 

 

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