Non-Newtonian substance uses 75% less fabric than previous body army, weighs less, and is half as thick

 By Brian Santo, contributing writer

stock_Goo

Nobody has ever looked at ketchup, Silly Putty, or castor
oil and thought “hey, I wonder if that stuff is bulletproof?” Which is one
reason why it has taken so long to stumble on an impact-resistant material that
could prove extremely effective for body armor, military vehicle cladding, mortar-defying
tents, emergency blankets, and any number of other possible uses. 

Researchers
at the US Air Force Academy (AFA) have devised a material that can stop a
bullet from a .44 Magnum, uses 75% less fabric than previous body army, weighs
less, and is half as thick, according to the AFA.

During a 2015 chemistry class at the Air Force Academy,
cadets were handed three impact-resistant materials – Kevlar, carbon fiber and
epoxy – and were asked to combine the materials to make a more effective
bulletproof material. 

As Cadet 1st Class Hayley Weir and her advisor, Ryan Burke,
a military and strategic studies professor at the academy, began working with
the materials, they became unsatisfied with the performance of the epoxy in the
trio of materials.

Epoxy happens to be a non-Newtonian fluid. The vast majority
of fluids in the world conform to Newton’s Law of Viscosity, which predicts the
behavior of fluids in response to the application of force. Non-Newtonian
fluids simply don’t conform to the law of viscosity. A factor in the equation
for viscosity is shear stress, and the shear stress characteristics of
different non-Newtonian fluids can vary wildly. Many of them, such as epoxy,
stiffen in response to force.

Weir and Burke began searching for another material in the
same class, with shear stress characteristics similar but superior to those of
epoxy.

Considering the total number of fluids, there aren’t that
many non-Newtonian fluids, but the substances that do fall in that category are
not rare. They include Silly Putty, ketchup, castor oil, custard, whipped cream,
some clays, latex paints, blood, and printer ink, among others.

Weir has told several sources that she remembered playing
with Oobleck, a simple
combination of corn starch and water, when she was a child. Oobleck happens to
be another non-Newtonian fluid.

It turned out that looking for another non-Newtonian fluid to
use in place of the epoxy was, in fact, a brainstorm. It seems an obvious idea,
but Weir and Burke couldn’t find reference to anyone else ever having tried it,
Burke told The
Air Force Times.

Weir and Burke found what they were looking for. They have
not identified the substance, which they’re referring to as “goo,” but it’s
black, and Weir mixes it up with a kitchen blender.

The material they’re using actually failed at first. The
researchers eventually discovered that how the layers of Kevlar and goo are
ordered make a difference, however. After changing the layering, they’re having
a hard time making it fail, they say.

Interestingly, the layered material gets harder with
increasing force. In practical terms, that means the bigger the bullet, the more
bulletproof the material is. The material was tested against rounds from a 9
mm, a .40 Smith & Wesson, and a .44 Magnum. In the 9 mm testing, the rounds
went through most of the layers but were caught by the fiber backing, Burke
told the Air Force Times. The larger .40-caliber round was contained in the
third layer of Kevlar. The .44 Magnum was caught in the first layer.

Weir and Burke recently spoke with reporter Kyle Clark of
Channel 9 in Denver, Colorado. The interview includes slow motion video of one
of their ballistic tests. See it below: