American football has both the highest rate of concussion incidences as well as the highest number of concussions of all contact sports due to both the number of athletes and nature of the sport. Recent research has linked concussions with long term health complications such as chronic traumatic encephalopathy and early onset Alzheimer’s. Understanding the mechanical characteristics of concussive impacts is critical to help protect athletes from these debilitating diseases and is now possible using helmet-based sensor systems. To date, real time on-field measurement of head impacts has been almost exclusively measured by devices that rely on accelerometers or gyroscopes attached to the player’s helmet, or embedded in a mouth guard. These systems monitor motion of the head or helmet, but do not directly measure impact energy. This paper evaluates the accuracy of a novel, multifunctional foam-based sensor that replaces a portion of the helmet foam to measure impact. All modified helmets were tested using a National Operating Committee Standards for Athletic Equipment-style drop tower with a total of 24 drop tests (4 locations with 6 impact energies). The impacts were evaluated using a headform, instrumented with a tri-axial accelerometer, mounted to a Hybrid III neck assembly. The resultant accelerations were evaluated for both the peak acceleration and the severity indices. These data were then compared to the voltage response from multiple Nano Composite Foam sensors located throughout the helmet. The foam sensor system proved to be accurate in measuring both the HIC and Gadd severity index, as well as peak acceleration while also providing additional details that were previously difficult to obtain, such as impact energy.
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This material and research are based upon work supported by the National Science Foundation under Grant Numbers CMMI-1538447 and IIP1549719. All helmet testing was performed at Virginia Polytechnic Institute and State University’s Biomedical Engineering and Mechanics helmet testing lab.
Associate Editor Karol Miller oversaw the review of this article.
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Merrell, A.J., Christensen, W.F., Seeley, M.K. et al. Nano-Composite Foam Sensor System in Football Helmets. Ann Biomed Eng 45, 2742–2749 (2017). https://doi.org/10.1007/s10439-017-1910-9
- Football helmet
- Impact detection
- Piezoelectric foam
- Self-sensing foam
- Impact energy
- Impact velocity
- Severity index