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SHRIMP WALLOP INSPIRES COMPOSITE DESIGN

THE PEACOCK mantis shrimp Odontodactylus scyllarus is native to the Indo-Pacific from Guam to East Africa. A large shrimp growing to 7 in. long, it has feelers that are so club-like they can shatter glass aquarium walls. These natural hammers are helping engineers formulate better and stronger composite structures. This, from my weekly Science magazine, Vol. 336, 8 June 2012, published by the American Association for the Advancement of Science.

The reddish clubs are the dactyl appendages of the peacock mantis shrimp. And club-like they are, capable of shattering glass aquarium walls.

These shrimp clubs have evolved as a composite of three separate parts. The outer shell, the “impact region,” consists of calcium phosphate, a compound also found in tooth enamel. It’s hard, yet derives its fracture resistance from interlayering of another material, chitosan, a natural polymer.

This thin outer shell is backed by a “periodic region.” Here, additional chitosan polymers are stacked at angles rotating through 180 degrees, this directionality giving excellent fracture resistance. (Any crack is forced to change direction, thus retarding its spread.)

Last, the periodic region is supported at its edges by a “striated region” contributing resiliency.

Materials engineers have fabricated composites along these multi-layered lines. And to really good effect: By interlacing titanium dioxide, TiO2, with a softer polymer, they’ve devised a nanocomposite that’s more than four times as tough as monolithic TiO2. Enhanced armor, lighter, yet more protective, could be one application.

In fact, Roman soldiers predated this biomimicry with their testudo, or tortoise, formation. Overlapping shields provided the outer shell. What’s more, each shield had layers with wood grains alternating between vertical and horizontal.

Excellent engineers that they were, the Romans exploited composite design in their soldiers’ testudo formation.

Alas, the soldiers themselves were expected to provided the elastic substructure.

ds

© Dennis Simanaitis, SimanaitisSays.com, 2012

 

3 comments on “SHRIMP WALLOP INSPIRES COMPOSITE DESIGN

  1. Dots
    August 17, 2012

    If you put 15 Bertone Testudos together would it work the same?

  2. Tom Tyson
    August 18, 2012

    When teaching structural composite repair to new Airframe & Powerplant students we introduce them to the concept of “clocking” the laminate layers. Part of the data supporting the repair of a damaged part or fabrication of a new part is a complete lamination schedule, which must include not only the weight and types of the fabric layers in an area of the part, but the orientation of the weaves as well. Properly designed and executed, the flow of forces through a part can be handled with minimal excess weight. It’s not something most people think about, but it can be a thing of beauty.

  3. Tom Tyson
    August 18, 2012

    [Topic Creep] Dots, I’m not quite sure that stacked Corvairs is quite what the authors had in mind, though it does bring back memories of the parking lot at the Milwaukee State Fairground (home of the “Milwaukee Mile”) in the middle of winter. The city of Milwaukee, in an effort to keep the roads cleared of snow would haul off and stack cars that were parked on the wrong side of the road they were plowing, often four or five high. Severe as it might sound, when you are dealing with five to seven feet of snow in a short period of time everyone has to cooperate to keep things like emergency services running. There is a educational period at the beginning of the winter when the offending cars are tagged and not towed. But once the snow begins in ernest, the schedule for which side of the road is being cleared each night is rigidly enforced.

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This entry was posted on August 17, 2012 by in Sci-Tech and tagged , , , , .
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