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May 9, 2012

Laboratory Setting Standards for 'SMART' Helmets

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As part of the SMART-TE program, APL engineers are putting combat helmets through ballistics tests to measure how well they protect against bullets and bomb fragments. Credit: JHU/APL

In recent years, combat-helmet manufacturers have taken steps to make their products more comfortable and effective in protecting the warfighter from head injury. APL is helping the Marine Corps Systems Command develop procedures to test and evaluate the best of these designs. This summer, engineers in the Research and Exploratory Development Department (REDD) will produce a set of comprehensive methodologies for designing and evaluating the next generation of protective headgear.

"The protection afforded by a combat helmet depends on its ability to mitigate head injuries due to a variety of threats, including ballistic impacts, blunt trauma, and shockwaves from explosions," explains REDD’s Andrew Merkle, manager of the APL's Biomechanics and Injury Mitigation Systems (BIMS) program. "But the helmet system must also remain stable on the head during operations and maximize comfort to ensure proper use at all times."

"Protecting the warfighter has always been a critical component of the Marine Corps’ mission," Merkle continues. "But the detailed design of helmets has become a significant focus in recent decades. The military has advanced the understanding of helmet suspensions—from sling systems to pad systems—and retention systems that secure the helmet to the head. We are finding that certain design details can drastically alter helmet performance and be the difference in predicting injury."

With the Suspension Materials and Retention Technologies Test and Evaluation (SMART-TE) effort, APL is taking a holistic approach to evaluating a helmet's suspension (how it sits on the head) and retention (how it stays on the head) components, says SMART-TE Project Manager Scott Swetz.

"When we looked at existing helmet safety studies, we found that the majority considered only certain elements of protection, and some bypassed important measures such as fit and comfort," Swetz says. "If the helmet is not comfortable, it may not be worn properly and therefore won’t provide the appropriate protection. The same goes for stability. If a helmet moves around during action, the warfighter could have compromised peripheral vision, be subjected to shrapnel and other dangers. All of these areas are equally important."

The SMART-TE team developed test protocols for blunt, ballistic, and blast impacts; for helmet stability and retention; and for comfort. They reviewed more than 20 state-of-the-art helmet systems, then selected five candidate systems and subjected them to the protocols developed as part of this project.

In the Impact Biomechanics Facility, the team is simulating the forces that a soldier might experience during head impact. "We have a single-axis rail system and attach an instrumented head form—outfitted with a helmet system—to it," Swetz explains. "We drop it onto a calibrated surface and measure the acceleration that would be imparted to the head. We have the capability here to evaluate the helmet’s performance when subjected to the operational spectrum of environments and threats."

In the Materials Characterization Facility, the SMART-TE team is testing helmets for comfort and stability. The ballistic testing—measuring the forces imparted to the head when a round is fired—is being performed in conjunction with a Department of Defense accredited ballistics testing facility.

All of these tests use a variety of human-like head forms, some created by the Laboratory, some adapted by the Laboratory, explains Liming Voo, a senior technical analyst with the program. "Each head form is the same shape but physically different, because they are adopted into different types of tests and measure different performance factors."

The engineers on the team are drawing on APL’s extensive experience in human injury biomechanics, armor systems, and testing and evaluation to complete the task, which is a major thrust of the BIMS program.

"This effort doesn’t stop at testing and evaluation," Merkle says. "The short-term goal is to establish the methodology and test existing solutions to find out what works and what doesn’t. But the long-term goal is to go back to industry and offer the lessons learned in an effort to shorten the design cycle and more rapidly advance the state of the art in head protection. If we can get manufacturers on board and help them create novel designs that truly take a revolutionary step forward, then that’s a success."