John DesJardins, assistant professor in bioengineering at Clemson, notes that most improvements in football helmets have focused on padding or adjustments to the shape, not the shell materials. “Historically, the thought was that the shell was simply too thin to provide any effective impact protection, and the only way you could make it provide more protection was to make it thicker. Thicker means heavier,” says DesJardins. Researchers at Clemson are working on composite shell materials because they are light weight and can better protect athletes.
While Innegra tests bending stiffness and strength of the materials, DesJardins will conduct testing on the impact response of the composite laminates at Clemson with Gregory Batt, an instructor in the department of food, nutrition and packaging science, and Natalie Patzin, a masters student in bioengineering. Clemson’s tests consist ofcreating a high-intensity shock event generated by dropping a weight on a supported sample. The team uses an accelerometer to record the material’s response upon the weight’s impact. A high-speed camera visually slows down the impact event, allowing the team to capture the impact and rebound velocity for the calculation of the coefficient of restitution and measure the actual deflection of the composite sample. For now, testing is performed on flat panels; later the researchers will evaluate curved prototypes and, eventually, actual helmets.
The researchers plan to evaluate and categorize a wide range of composite configurations based on the Innegra fiber’s ability to absorb impact energy. “With composite materials, there are many different material design factors that can be used to make the optimum material for a particular application,” DesJardins says. “The greatest challenge in this project will be to use our initial testing data to select the specific material and composite design from which to produce candidate helmets for final testing and evaluation.”
The partnership is expected to last into early 2015. Innegra Technologies and B&W Fiber Glass, who together manufactured and commercialized hybrid yarns for the study, see opportunities for the materials to be applied in a variety of areas in which safety is a concern. This includes sporting equipment and automobiles. “A football player’s head impacting the turf will be different than a whitewater kayaker’s head impacting a rock or a hockey player’s head impacting the ice,” Batt remarks. “There is clearly further work that could be done in pairing the best composite material for the variety of sport-related impact events that could occur.”