Lawrence Livermore National Laboratory (LLNL)
have found that soldiers
using military helmets one size larger and with thicker pads could
reduce the severity of traumatic brain injury (TBI) from blunt and
Their results came after a one-year study funded by the U.S. Army and
the Joint IED Defeat Organization (JIEDDO) to compare the effectiveness
of various military and football helmet pads in mitigating the severity
The findings have been presented to the Program Executive Office (PEO)
Soldier, which is directed by Brig. Gen. Peter Fuller and is the U.S.
Army acquisition agency responsible for everything a soldier wears or
In 2009, Gen. Peter Chiarelli, of the Vice Chief of Staff of the Army,
directed JIEDDO to review the mitigation capabilities of the U.S. Army's
Advanced Combat Helmet (ACH) against impact injuries. LLNL researchers
Willy Moss and Mike King were tasked to determine if the helmet pads
used by the NFL might protect against militarily relevant impacts better
than the pads currently used in the ACH.
"A review committee chose us to do this study based on our previously
published work on blast-induced TBI. The committee concluded that LLNL
had the best mix of skills and capabilities to quickly and effectively
address the Defense Department's concerns," Moss explained.
Five types of pad systems were studied-those currently and previously
used by the Army, two used in NFL helmets, and one used in other
protective sports equipment. The two Army systems consist of bilayer
(hard-soft) foam pads within a water-resistant airtight wrapper or
coating. One NFL system consists of a thin foam pad and a hollow
air-filled cylinder that buckles under load, and the other is a bilayer
foam pad surrounded by a covering with air-relief channels that connect
to adjacent pads in the helmet. The fifth pad consists of uniform dense
Moss and King used a combination of experiments and computational
simulations to study the response of the various pad systems to
battlefield-relevant impacts to gain an understanding of how helmet pads
provide protection against these impacts.
"For each of the pads, we did experiments to characterize the material
properties of the individual foam components as well as the response of
the complete pad system to a range of impact velocities," King said.
"Then we did a large number of computational simulations examining how
various parameters, such as foam material, pad thickness, pad area, and
trapped air, affect the overall impact response. We also performed
simulations of actual military helmet drop tests to confirm the validity
of our computational methods and results."
The impact response simulations made use of the PARADYN finite element
analysis software, a parallel version of the DYNA3D software developed
by LLNL in the 1970s and 80s to model the deformation of solid
structures under impact. (DYNA3D has been commercialized as LS-DYNA and
is used worldwide by automotive, aerospace, bioengineering,
manufacturing, and construction industries.)
The LLNL study found that for comparable thicknesses, none of the pads
examined outperforms the pad currently used in the ACH system for
battlefield-relevant impacts. The experiments and simulations confirmed
that pad performance depends on impact velocity, with softer pads
performing better at lower impact velocities and harder pads providing
more protection at higher velocities. Because the NFL pads are not as
soft as the military pads, they allow larger forces to be transferred to
the head. This finding was not completely unexpected since football
impacts differ from military impacts, so the requirements for the
respective pads are different.
"Just because no pad in this study outperforms the pad that's currently
used in the ACH doesn't mean that an improved system can't be devised,"
The most important result of the study was that significantly increased
protection could be attained by modest increases in pad thickness. The
current military pad is about three-quarters of an inch thick. Moss and
King found that increasing pad thickness by an extra eighth to quarter
inch could make a large difference in reducing the accelerations
imparted to the head. Implementing such a change would require no
"system reconfiguration," but simply the use of a one-size-larger helmet
with correspondingly thicker pads.
Use of a one-size-larger helmet also would provide additional protection
against non-penetrating bullets or metal fragments, due to the extra
space into which the inside surface of the helmet could expand without
contacting the head.
"What we found amazing was that our results suggest a very-low-cost
strategy for mitigating TBI that the Defense Department could implement
immediately, providing there's no detriment to functional or operational
requirements," said Moss.
"Our methods and results also are applicable to the civilian sector,
particularly contact sports helmet design," King added. The NFL, as well
as college and youth sports organizations, have increased efforts to
find better ways to protect their athletes from head trauma.
"A combination of simulation and experiment like we've used here also could
be used to evaluate and improve the design of various sports helmets.
It's very gratifying that this work can help protect our soldiers in the
field and also benefit professional and youth athletes."