Head Strong: ARL Team Determined to Find New Solutions for Improved Soldier Helmet Systems
May 11, 2010
ARL is passing on groundbreaking research findings in helmet technology to military, industry, modeling and simulation, and medical communities. A team of researchers is developing new head protection materials, systems, and concepts; and developing new cost-effective manufacturing technologies to enable fielding next-generation combat helmets to Soldiers.
The team's combined efforts, which included working with Natick Soldier RDEC and PM Soldier, successfully produced a ballistic helmet shell that exhibits an average of 35 percent improved ballistic protection as compared to the current state-of-the-art Army Combat Helmet. The Enhanced Combat Helmet is expected to be introduced and fielded to Soldiers and Marines in active theater operations once final production is completed by the ECH contractors.
"With the events that are occurring in Iraq and Afghanistan, we found that some of the technologies that we've been developing for other applications had potential use in helmet technology," said Dr. Shawn Walsh, who leads ARL's Agile Manufacturing Technology Team efforts in head protection and serves as coordinator of the integrated team. He added that ARL became involved with this personal protection research effort in part because of awareness of maturing technologies, such as ultra highly molecular weight polyethylene materials, a kind of thermoplastic that offers a significantly better material for the helmet.
"We've made the investment to capitalize on these technologies," Walsh noted. "The precipitation of this research came from the idea of trying to exploit these new materials in new systems."
As part of the research effort, ARL scientists pioneered a molding process to pre-form the thermoplastic material. ARL's unique pre-form methodology has transformed the current U.S. industrial manufacturing base for ballistic helmet material, which had not changed significantly since Kevlar was first introduced in the early 1970s.
The pre-form assembly machine is the only one of its kind, Walsh said, and it combines layers of the material into lightweight helmet shells. DoD awarded its highest manufacturing technology honor, the Defense Manufacturing Achievement Award, to Walsh and his team in December 2009 for these and other contributions to improved helmet manufacturing.
Thermoplastic materials are tested to study whether or not they can stop a projectile and to determine what happens to the material in the process. Alternating the direction of the materials in the pre-form process, based on its fiber pattern, can optimize ballistic performance, explained Peter Dehmer, a materials engineer in ARL's Ceramics and Transparent Materials Branch.
Dehmer is also considered ARL's pioneering adopter of Digital Image Correlation (DIC) technology. DIC is a technique that uses two high-speed cameras to stereoscopically track the movement in space of a grey scale or "dot" pattern applied to a surface of interest. As part of ARL's studies, helmet linings are marked with a series of dots. During ballistic impact tests, the cameras and software can determine the 3-D coordinates of specific surface locations in the dot pattern as they shift relative to each other over time. The DIC software allows researchers to click on any single data point within the dot pattern and immediately see its time history.
Inside the Ceramics and Transparent Materials Branch laboratory, an improvised gun unit combined with DIC technology is used to measure displacement and calculate velocity and in-plane strain in projectile impact tests.
DIC is also an essential experimental technology deployed within ARL's Systems Engineering and Experimentation Branch, which is leading research that experimentally replicates and dynamically measures helmet back face deformation. One anticipated outcome of this study, according to chief researcher Dixie Hisley, is that information can be correlated to injury criteria by the medical and/or modeling and simulation communities, which all have interest in better understanding the causes of a variety of head injuries.
In addition to DIC technology, ARL researchers rely on data from instrumented head forms, or helmet test fixtures. Their studies look at how a bullet's energy upon impact is absorbed by the Kevlar and thermoplastic-based combat helmets.
"The absorption of energy often results in a bulge that could grow two to three inches or more toward Soldiers' heads," Hisley explained. She added that accurate, repeatable physical response measurements of the speed, force applied, and the area of contact on the head of the bulge, could eventually result in a standard that correlates dynamic physical response measurements to blunt trauma injury criteria.