Clemson researchers use linear impact testing machine to help determine future of football helmet facemasks

CLEMSON, S.C. – Fall, football and facemasks.

While the most talked about facemasks this year are worn to protect people from the COVID-19 virus, Clemson University researchers continue their quest to determine how future designs of football helmet facemasks can help improve these helmets and the overall safety of players. And, they have received a new machine to help in their facemask design efforts.

The researchers are Gregory Batt, an associate professor in food, nutrition and packaging sciences and director of the Clemson Transport Package Testing Laboratory; John DesJardins, a professor of bioengineering and director of the Laboratory of Orthopaedic Design and Engineering; Tessa Gagne, a master’s student who also is a graduate research assistant in food, nutrition and packaging sciences; and Davis Ferriell, a bioengineering doctoral student. Joining them in the study is Jay Elmore, owner of Green Gridiron in Greenville.

The team recently received funds to purchase a linear impact testing machine to use in addition to a linear drop tower currently being used. This new machine allows the researchers to simulate more impactful collisions.

“The linear impact testing system is kind of like a fancy air cannon that you can use to accurately shoot things at each other,” said DesJardins, who also is the Robert B. and Susan B. Hambright Leadership associate in the Clemson Bioengineering Department. “We are using it recreate helmet impacts that are seen on the football field and, then, see how the helmet and dummy headform move.”

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Headforms are dummy human heads equipped with plates and sensors to provide data on how impacts and forces affect different parts of a head. The linear impact testing machine provides more realistic testing simulations of football helmet impacts that can occur from head-to-head collisions and cause concussions or other traumatic brain injuries (TBIs). It was acquired after Batt and DesJardins received a grant through the Clemson University Major Research Instrumentation-MRI) Program. Additional money came from the Clemson University Department of Mechanical Engineering, Department of Bioengineering, and the Department of Food, Nutrition and Packaging Sciences.

“Studies have shown that rotational acceleration plays a larger role in mild TBIs than linear accelerations,” Ferriell said. “This linear impact testing system allows us to recreate impacts that more accurately produce rotational accelerations, whereas, the linear drop tower just allows us to simulate linear acceleration conditions.”

Linear and rotational accelerations are forces that act on the brain when the head rapidly accelerates or decelerates, or when there is a rapid change in movement of the head, such as when a football player is tackled. Batt said there are several different situations on a football field that cause rapid changes in velocity, or g-forces, applied to a player’s head.

“These situations can be player-to-player or player-to-turf interactions,” Batt said. “These rapid changes in velocity can cause a player’s brain to move around inside the player’s skull potentially causing brain injury.”

The team’s research involves establishing a testing system that differentiates between facemask performance and helmet performance. The goal is to understand and evaluate the role a football helmet facemask plays in the overall impact performance of a football helmet system.

The research team has developed a system to test facemask stiffness and is working on computational models to assist in future facemask designs. By measuring facemask stiffness during impact, the team is able to understand how the helmet system will perform on the field and protect players. This system differentiates between individual facemask designs, materials and impact location. Perhaps most importantly, the research team has been able to measure decreases in impact performance of the facemask after prolonged use.

The team also is working to help make helmets safer by creating a facemask that can help the helmet transfer forces away from the head. Traditional helmet design produces protective equipment that gradually decelerates the head upon impact. Facemasks prevent direct contact with players’ faces.

The facemask tests

The facemask tests are being conducted in the Clemson Headgear Impact Performance Laboratory (CHIP Lab) of the Clemson Package Dynamics Laboratory on the Clemson campus. Variables studied include structural stiffness, resistance to permanent deformation and energy absorption.

The linear drop tower is used to measure variables associated with the overall performance of facemask designs, including helmet padding structure, helmet outer shell and the chin strap buckles.

The new linear impact testing machine allows the researchers to better analyze helmets and facemasksin accordance with current industry standards set by the National Operating Committee on Standards for Athletic Equipment (NOCSAE) and the National Football League (NFL) Helmet Challenge.

The team also uses high speed video and accelerometersto measure sudden movements of the helmet and headform. Accelerometers allow researchers to measure how quickly something changes direction when it is hit or moved. For example, accelerometers allow smartphones to rotate the display between portrait and landscape depending on how the phone is tilted, and detect crashes and deploy airbags in automobiles.

Head injuries are a leading cause of death and severe injury for players in contact sports such as football. According to the National Institutes of Health, repeated sports-related head injuries increase risks of future concussions, cerebral swelling, acute subdural hematoma (blood clot on the brain) and chronic traumatic encephalopathy (brain disease caused by repeated TBIs).

Data from the U.S. Consumer Product Safety Commission’s National Electronic Injury Surveillance System (NEISS) estimates 292,306 people with football-related head injuries were treated in U.S. hospital emergency rooms in 2019. Of these, 285,199 were treated and released while 7,107 died. The CDC reports about 75% of TBIs that occur each year are concussions or other forms of mild TBI.

Traumatic brain injuries can cause a wide range of short- and long-term changesincluding those in memory and reasoning, as well as communication, expression and understanding. The CDC reportsrecovery from mild head injuries requires rest and a slow, gradual return to daily activities, such as work or school. Head injuries can cause student athletes to struggle with their academic studies. A study by the American Society for Sports Medicine shows student athletes who suffer from head injuries or concussions may require specialacademic accommodations including reduced workload and extended time for tests while recovering. Clemson students needing special accommodations can check with Student Accessibility Services.

In addition to sports, falls and motor vehicle crashes also contribute to a large number of TBIs.

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