Stronger, Lighter Soldier Armor From Nanoscale Experiments
by Army Research Laboratory Public Affairs
U.S. Army Combat Capabilities Development Command
June 1, 2020
Soldier armor, such as bulletproof vests and helmets, depends
upon high-performance ballistic fibers for its strength and
U.S. Army Sgt. Michael Graham, 4th Infantry Division, wears an Improved Outer Tactical Vest. Army scientists conduct basic research on high-performance fibers with the goal of making future armor even stronger and lighter. (U.S. Army courtesy photo)
Army researchers are experimenting with how they can improve
armor by making it lighter and stronger. At the U.S. Army Combat
Capabilities Development Command’s Army Research Laboratory,
researchers examine high-performance fibers in an innovative soft
armor research program.
By understanding how fibers behave
under stress, researchers can predict their performance during a
ballistic event. With this information, researchers can leverage a
materials-by-design approach to create stronger, more effective body
The Army researchers partner with U.S. industrial
fiber manufacturers to study about the structure inside single
fibers and how it influences the strength and stiffness of the
fibers.Atomic force microscopy examines material surfaces at the
extremely small scale ... on the order of fractions of a nanometer.
Strawhecker uses the analogy of a tiny version of a blind man
tapping his cane along the inside of the fiber. This is how atomic
force microscopy maps the fibrils for length and width, he said.
The researchers discovered that these fibrils tend to form
bundles of fibrils.
These findings leave the researchers optimistic that as they look
at smaller and smaller structures within a fiber, they will
understand what holds them together.
“Long polymer molecules
form crystals which group into nano-fibrils, which group into fibril
bundles, which group into single fibers,” Strawhecker said. “At each
size we have found that there is a similar resistance to separation
between these parts for a fiber with given chemical makeup and
Understanding this structure means
knowing how molecules are arranged together to form structures that
ultimately will stop a bullet for the Soldier.
the best way to arrange them can be based upon these models and it
depends on finding the strongest, stiffest overall fiber structure
due to the arrangements within,” he said.
The American Chemical Society published this research as a cover
in its Applied Materials & Interfaces, May 13, 2020, Vol. 12, Issue
19. The lead author for the paper, Dr. Taylor Stockdale, performed
many of the experiments as a doctoral student at the University of
Nebraska-Lincoln using techniques learned as an intern with
Strawhecker at the lab’s Rodman Materials Research Laboratory during
the summer of 2015.
Stockdale learned how to use the lab’s focused-ion beam
instrument to shoot a beam of gallium ions at a fiber to mill out
notches in the fiber. With those notches in place, he carefully used
an ultra-fine platinum wire (typically used by a scanning
transmission microscope to image atomic features) to dig-out and
unzip the top half of the fibers, uncovering their interior ... like
opening a convertible automobile, Strawhecker said.
Strawhecker said the initial work earned now-Dr. Stockdale the 2015
Army Research Laboratory Graduate Student Summer Internship award
for Best Paper and resulted in the seminal publication of the
Besides U.S. fiber manufacturers,
collaborative partners include the University of Nebraska-Lincoln,
Northeastern University, CCDC Soldier Center, University of Delaware
and Drexel University.
The Army goal is to make armor lighter
and reduce bulk and burden on the warfighter.
fundamentally approaches the building block of armor packages, which
comprises a large percentage of the overall Soldier burden.
As new experimental fibers are being produced, he said, the
laboratory will continue to partner with manufacturers using these
special techniques to understand how new chemistry and processing
steps may change the structure and performance of the next
generation of fiber materials.
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