Adaptive head impact protection via a rate-activated helmet suspension

Spinelli, Devon J.; Plaisted, Thomas A.; Wetzel, Eric D.

doi:10.1016/j.matdes.2018.04.083

Cited by 11 publications

(12 citation statements)

References 53 publications

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“…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.…”

Section: Introductionmentioning

confidence: 99%

Collapsible fluid-filled fabric shock absorber with constant force

Alizadeh

Fanton

Camarillo

2021

Journal of Intelligent Material Systems and Structures

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Energy absorption is an important challenge shared by multiple different industries including manufacturing, transportation, and protective equipment. This paper presents a novel shock absorption system based on woven fabrics designed to fully collapse and absorb energy at a near-minimum force level. The proposed system exerts an approximately constant force across different impact velocities. This system utilizes a fixed-orifice hydraulic shock absorber with variable contact area over its displacement to provide a nearly-constant force which scales with impact energy. Using analytical fluid dynamics, the contact area needed to produce a constant minimum force is derived. A finite element model of this shock absorber is created to validate the concept. Different impact conditions are simulated. The results confirm that the proposed fabric shock absorber is capable of producing a nearly-constant force across different impact energies. In simulation, the fabric shock absorber follows the ideal constant force profile with an averaged efficiency of 77.8% ± 3.4% which is far above standard foams which have efficiency of only approximately 20%–40%. The proposed system is compared with a cylindrical damper to show performance improvements gained through variable area geometry. Potential applications of this technology include soft devices for space-constrained applications such as contact sport helmets.

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Section: Introductionmentioning

confidence: 99%

Collapsible fluid-filled fabric shock absorber with constant force

Alizadeh

Fanton

Camarillo

2021

Journal of Intelligent Material Systems and Structures

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“…An ideal energy absorber is a smart material or structure which minimizes the peak force necessary to absorb impact energy given a stroke length, and must have the following characteristics. First, it must exert a constant force over the full stroke length [2,3]. With a constant force, the force level is inversely proportional to the utilized stroke length.…”

Section: Introductionmentioning

confidence: 99%

“…To obtain a true constant force level, the rise time of the force must be as fast as possible. Second, an ideal absorber must exert a magnitude of force that scales with the impact energy in order to absorb this energy at a minimum force level regardless of impact speeds [2,4].…”

Section: Introductionmentioning

confidence: 99%

Variable area, constant force shock absorption motivated by traumatic brain injury prevention

Fanton

Alizadeh

Domel

et al. 2020

Smart Mater. Struct.

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Compact and efficient energy absorption is desirable for numerous applications including manufacturing, transportation, and protective equipment. An ideal shock absorber is a smart material or structure that can adapt its force-displacement properties to minimize the peak impact force regardless of the impact energy. While traditional shock absorbers can produce precisely-tuned ideal force profiles, they are rigid devices that only compress half of their total length, limiting utility in space-constrained applications. Energy absorbers that are soft and collapsible, such as foams, do not have ideal force profiles and generally have insufficient viscoelasticity to adapt to different impact energies. Here, we present a smart structure concept-variable area shock absorption (VASA)-that leverages a changing contact area in a hydraulically damped collapsible system to passively adapt the force to the minimum necessary to absorb the energy of an impact. Using an analytical fluid dynamics model, we derived the contact area as a function of compression to produce a constant force over the entire stroke of a fixed-orifice damper, and validate this concept experimentally using a preliminary 3D-printed prototype. The VASA prototype follows the constant force profile with a NRMSE between 0.02-0.25 at impact speeds between 2.3 and 4.3 m s −1 . This new approach for absorbing energy is compatible with full collapse of the absorber, enabling soft devices for space-constrained applications in future work. Potential applications include helmets that must absorb energy at a near-minimum force level across multiple impact energy levels.

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“…Blunt impacts have also been studied for bicycle 17,18 motorcycle, [19][20][21][22][23][24] sport (football/lacrosse/ equestrian) [25][26][27][28][29] and industrial applications. [30][31][32] The effect of foam density on the peak linear acceleration of the headform for expanded polystyrene (EPS) lined bicycle helmet was studied using a FE model. 17 Others have considered suspension systems incorporating shear thickening fluid, 30 latticed structured, 19 agglomerated cork and honeycomb liners 21 for motorcycle 23 or industrial applications.…”

Section: Introductionmentioning

confidence: 99%

“…[30][31][32] The effect of foam density on the peak linear acceleration of the headform for expanded polystyrene (EPS) lined bicycle helmet was studied using a FE model. 17 Others have considered suspension systems incorporating shear thickening fluid, 30 latticed structured, 19 agglomerated cork and honeycomb liners 21 for motorcycle 23 or industrial applications. Little work has been done previously to investigate the complex relationship between foam suspension pad size, placement, and stiffness on the blunt impact performance of combat helmets.…”

Section: Introductionmentioning

confidence: 99%

Combat helmet liner design for blunt impact absorption using multi-output Gaussian process surrogates

Barlow

Page

Drane

et al. 2020

Proceedings of the Institution of Mechanical Engineers, Part C:

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A finite element based computational model simulating the standard drop tower test for military helmets was created and used in conjunction with a multi-output Gaussian process surrogate to seek different designs of helmets for improved blunt impact performance. Experimental drop test results were used for the validation of the model’s ability to simulate impact. The influence of foam stiffness, impact velocity, strap tension, as well as pad placement and size on parameters on the peak linear acceleration (PLA) of the headform was investigated for the first time through a surrogate model trained by strategically choosing simulation points. Impact velocity was found to have the greatest effect. The strap tension and foam pad stiffness ranges examined within this sampling plan were found to have less of an effect on the performance of the helmet than the pad size and shape parameters examined. The surrogate modeling approach was used to quantify the influence of design parameters and can lead to not only improved helmet designs but also new data-driven design metrics and testing standards to accelerate the development of TBI-mitigating helmets.

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Adaptive head impact protection via a rate-activated helmet suspension

Cited by 11 publications

References 53 publications

Collapsible fluid-filled fabric shock absorber with constant force

Collapsible fluid-filled fabric shock absorber with constant force

Variable area, constant force shock absorption motivated by traumatic brain injury prevention

Combat helmet liner design for blunt impact absorption using multi-output Gaussian process surrogates

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