A Computational Study of Liquid Shock Absorption for Prevention of Traumatic Brain Injury

Abstract

Mild traumatic brain injury (mTBI), more colloquially known as concussion, is common in contact sports such as American football, leading to increased scrutiny of head protective gear. Standardized laboratory impact testing, such as the yearly NFL helmet test, is used to rank the protective performance of football helmets, motivating new technologies to improve the safety of helmets relative to existing equipment. In this work, we hypothesized that a helmet which transmits a nearly constant minimum force will result in a reduced risk of mTBI. To evaluate the plausibility of this hypothesis, we first show that the optimal force transmitted to the head, in a reduced order model of the brain, is in fact a constant force profile. To simulate the effects of a constant force within a helmet, we conceptualize a fluid-based shock absorber system for use within a football helmet. We integrate this system within a computational helmet model and simulate its performance on the standard NFL helmet test impact conditions. The simulated helmet is compared with other helmet designs with different technologies. Computer simulations of head impacts with liquid shock absorption predict that, at the highest impact speed (9.3 m/s), the average brain tissue strain is reduced by 27.6% ± 9.3 compared to existing helmet padding when tested on the NFL helmet protocol. This simulation-based study puts forth a target benchmark for the future design of physical manifestations of this technology.

Liquid‐Crystal‐Elastomer‐Based Dissipative Structures by Digital Light Processing 3D Printing

“…In a recent biomechanical analysis of football helmets, Alizadeh et al discussed how ideal energy-dissipating materials would adjust their properties to maximize the stroke under all impact conditions. [7] Their study showed that under theoretically ideal conditions, concussions may be reduced by 73%. [7] The high rate-dependence and soft-elastic behavior of liquid-crystal materials may provide a means to help approach these ideal impact conditions.…”

“…[7] Their study showed that under theoretically ideal conditions, concussions may be reduced by 73%. [7] The high rate-dependence and soft-elastic behavior of liquid-crystal materials may provide a means to help approach these ideal impact conditions. When designing personal safety equipment or protective features for machines and electronics, it makes more sense to use a durable material that will be able to maximize energy dissipation while minimizing peak stresses across a range of loading conditions.…”

“…This includes sports and personal protective equipment as well as biomedical devices. [5,6,7] In this study we are the first to explore how liquid-crystalline materials with inherent dissipative behavior can be 3D printed to create energy dissipative structures.…”

The relationship between brain injury criteria and brain strain across different types of head impacts can be different

“…The possible explanations may be: (i) the laboratory impacts were generally simulated for the research of head impacts in football matches, which may explain the similarity between laboratory impacts and college football impacts; (ii) the MMA head impacts and NHTSA car crash dummy head impacts were measured without protective helmets, while the college football head impacts and the NASCAR head impacts were measured with protective helmets that protect the players/drivers from concussion. The helmet can effectively change the impact response of the head [51], which may explain the similarity between MMA impacts and NHTSA impacts, as well as among NASCAR impacts, college football impacts and laboratory impacts.…”

Collapsible fluid-filled fabric shock absorber with constant force

“…An ideal shock absorber exerts a near-constant force over its full stroke length to absorb the energy of an impact (Baumeister et al, 1997;Fanton et al, 2020;Spinelli et al, 2018;Vahid Alizadeh et al, 2021). The necessary constant force level is inversely proportional to the usable stroke length; a longer stroke length allows the shock absorber to spread the force out over a longer displacement, allowing for a lower force level.…”