I3 - Head Armor Pro: Improving Youth Football Helmet Safety with a Porous Viscoelastic Design

Introduction: : Concussions are a major concern in youth football, commonly occurring with impacts that cause linear accelerations of 70-120 g and/or rotational accelerations of 5,582 to 9,515 rad/s². Research indicates that concussions occur irrespective of the point of impact [1]. The highest predictive occurrence of concussions has been observed at 96.1 g and 5,582 rad/s² [2]. Protective equipment can reduce the likelihood of a concussion by absorbing energy and reducing these accelerations [2]. Here we developed 3D printed porous materials to test and model their auxetic behavior which can increase impact energy absorption [4].

Materials and

Methods: : As a control, samples of foam from a Riddell Speed Icon youth helmet composed of Ethylene-Vinyl Acetate (EVA) were tested. The current Head Armor Pro geometry featuring a cu was printed using Formlabs Flexible 80A Resin (E = 4.0 MPa; ν = 0.13) and the Formlabs 3B+ SLA Resin Printer. All specimens had uniform thicknesses of 25 mm for dimensional consistency. The geometries were then subjected to compression tests using a Shimadzu Instron, which applied controlled, uniform displacement to test the material strain response. Plots were then generated based on the displacements during deformation of the foams. For the analysis of these deformation patterns, we employed MATLAB. Custom scripts were developed to process raw data and calculate key mechanical parameters. Each test was conducted in replicates (n = 6) to ensure reliability of the findings. Linear acceleration and Head Injury Criterion (HIC) values were measured using a linear drop test performed with an impact testing apparatus. Rotational acceleration was assessed using a custom-built pendulum setup, generating impacts from three distinct initial heights to simulate rotational impact severities relevant to youth football. Impact accelerations were recorded using an MPU 6050 accelerometer at a sampling frequency of 1000 Hz, enabling precise tracking of the data. Raw acceleration data was then processed and analyzed using custom-developed MATLAB scripts to accurately quantify impact responses. This methodology provided a comprehensive evaluation of the Head Armor Pro foam geometry’s ability to mitigate both linear and rotational accelerations associated with concussion risk.

Results, Conclusions, and Discussions:: Results and

Discussion: The Head Armor Pro (HAP) Foam demonstrated significantly enhanced mechanical stiffness and reduced linear and rotational accelerations compared to conventional EVA Foam across all test conditions (Fig. 1–2). Under compression, HAP Foam exhibited a steeper stress-strain profile at low strain, indicating a higher resistance to deformation (Fig. 1, left). In the Standard Linear Drop Test, HAP Foam consistently reduced Head Injury Criterion (HIC) values by approximately 60% across all impact velocities, highlighting its superior ability to attenuate linear forces (Fig. 1, right). Additionally, in Standard Pendulum Tests measuring rotational acceleration from front, side, and back impacts, HAP Foam reduced rotational acceleration by an average of ~43.4% relative to EVA Foam, regardless of drop height (Fig. 2). These results underscore the viscoelastic advantages of HAP Foam in both linear and rotational impact scenarios, supporting its potential as a safer alternative for head protection in youth sports.

Conclusions: These results emphasize the potential efficiency of viscoelastic materials in reducing concussion risks in youth football. Notably, the findings suggest that structurally viscoelastic materials—particularly those featuring the Hourglass geometry—could significantly advance the design of safer sports equipment. Furthermore, the use of 3D printing enables these designs to be integrated into commercially available helmets, offering a promising approach for enhancing protection in contact sports.

Acknowledgements and/or References (Optional)::

References: [1] Brennan+, Sports Medicine (2017); [2] Clark+, Sports Medicine (2017); [3] Foster+, Sports Materials (2018); [4] Najafi+, Materials Today (2021); [5] Lovell+, Journal of Sports Sciences (2016); [6] Oeur+, Journal of Neurosurgery (2015)