This beetle can survive getting run over by a car. Engineers are
figuring out how

Date:
October 21, 2020
Source:
Purdue University
Summary:
Getting run over by a car is not a near-death experience for the
diabolical ironclad beetle. How the beetle survives could inspire
the development of new materials with the same herculean toughness,
engineers show.



FULL STORY ========================================================================== Getting run over by a car is not a near-death experience for the
diabolical ironclad beetle.


==========================================================================
How the beetle survives could inspire the development of new materials
with the same herculean toughness, engineers show in a paper published Wednesday (Oct.

21) in Nature.

These materials would be stiff but ductile like a paper clip, making
machinery such as aircraft gas turbines safer and longer-lasting, the researchers said.

The study, led by engineers at the University of California, Irvine
(UCI) and Purdue University, found that the diabolical ironclad beetle's super-toughness lies in its two armorlike "elytron" that meet at a line,
called a suture, running the length of the abdomen.

In flying beetles, the elytra protect wings and facilitate flight. But
the diabolical ironclad beetle doesn't have wings. Instead, the elytra
and connective suture help to distribute an applied force more evenly throughout its body.

"The suture kind of acts like a jigsaw puzzle. It connects various
exoskeletal blades -- puzzle pieces -- in the abdomen under the elytra,"
said Pablo Zavattieri, Purdue's Jerry M. and Lynda T. Engelhardt Professor
of Civil Engineering.



==========================================================================
This jigsaw puzzle comes to the rescue in several different ways depending
on the amount of force applied, Zavattieri said. A video explaining
these findings is available on YouTube at https://youtu.be/NS3AqJB5SfU.

To uncover these strategies, a team led by UCI professor David Kisailus
first tested the limits of the beetle's exoskeleton and characterized
the various structural components involved by looking at CT scans.

Using compressive steel plates, UCI researchers found that the diabolical ironclad beetle can take on an applied force of about 150 newtons -- a
load of at least 39,000 times its body weight -- before the exoskeleton
begins to fracture.

That's more impressive than sounds: A car tire would apply a force of
about 100 newtons if running over the beetle on a dirt surface, the
researchers estimate.

Other terrestrial beetles the team tested couldn't handle even half the
force that a diabolical ironclad can withstand.

Zavattieri's lab followed up these experiments with extensive computer simulations and 3D-printed models that isolated certain structures to
better understand their role in saving the beetle's life.



==========================================================================
All of these studies combined revealed that when under a compressive
load such as a car tire, the diabolical ironclad beetle's jigsaw-like
suture offers two lines of defense.

First, the interconnecting blades lock to prevent themselves from pulling
out of the suture like puzzle pieces. Second, the suture and blades
delaminate, which leads to a more graceful deformation that mitigates catastrophic failure of the exoskeleton. Each strategy dissipates energy
to circumvent a fatal impact at the neck, where the beetle's exoskeleton
is most likely to fracture.

Even if a maximum force is applied to the beetle's exoskeleton,
delamination allows the interconnecting blades to pull out from the suture
more gently. If the blades were to interlock too much or too little,
the sudden release of energy would cause the beetle's neck to snap.

It's not yet known if the diabolical ironclad beetle has a way to
heal itself after surviving a car "accident." But knowing about these strategies could already solve fatigue problems in various kinds of
machinery.

"An active engineering challenge is joining together different materials without limiting their ability to support loads. The diabolical ironclad
beetle has strategies to circumvent these limitations," said David
Restrepo, an assistant professor at the University of Texas at San
Antonio who worked on this project as a postdoctoral researcher in
Zavattieri's group.

In the gas turbines of aircraft, for example, metals and composite
materials are joined together with a mechanical fastener. This fastener
adds weight and introduces stress that could lead to fractures and
corrosion.

"These fasteners ultimately decrease the performance of the system
and need to be replaced every so often. But the interfacial sutures of
the diabolical ironclad beetle provide a robust and more predictable
failure that could help solve these problems," said Maryam Hosseini, who
worked on this project as a Ph.D. student and postdoctoral researcher in Zavattieri's group. Hosseini is now an engineering manager at Procter &
Gamble Corp.

UCI researchers built a carbon fiber composite fastener mimicking a
diabolical ironclad beetle's suture. Purdue researchers found through
loading tests that this fastener is just as strong as a standard aerospace fastener, but significantly tougher.

"This work shows that we may be able to shift from using strong, brittle materials to ones that can be both strong and tough by dissipating energy
as they break. That's what nature has enabled the diabolical ironclad
beetle to do," Zavattieri said.

This research is financially supported by the Air Force Office
of Scientific Research and the Army Research Office through the Multi-University Research Initiative (award number FA9550-15-1-0009). The
study used resources at the Advanced Light Source, a U.S. Department of
Energy Office of Science User Facility.


========================================================================== Story Source: Materials provided by Purdue_University. Original written
by Kayla Wiles. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Jesus Rivera, Maryam Sadat Hosseini, David Restrepo, Satoshi Murata,
Drago Vasile, Dilworth Y. Parkinson, Harold S. Barnard, Atsushi
Arakaki, Pablo Zavattieri, David Kisailus. Toughening mechanisms
of the elytra of the diabolical ironclad beetle. Nature, 2020;
586 (7830): 543 DOI: 10.1038/s41586-020-2813-8 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/10/201021112341.htm

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