Evaluation of a novel bicycle helmet concept in oblique impact testing

Bliven, Emily; Rouhier, Alexandra; Tsai, Stanley; Willinger, Rémy; Bourdet, Nicolas; Deck, Caroline; Madey, Steven M.; Bottlang, Michael

doi:10.1016/j.aap.2018.12.017

Cited by 80 publications

(76 citation statements)

References 33 publications

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“…To the authors' knowledge, there are no peer-reviewed publications that have tested these products. A recent publication by Bliven et al features a helmet liner (WaveCel Concept) [41] for reducing rotational acceleration during oblique impacts. The liner resembles a double arrowhead auxetic structure, [42] although the authors neither refer to the design as auxetic, nor provide details of how it was manufactured.…”

mentioning

confidence: 99%

Validation of a Finite Element Modeling Process for Auxetic Structures under Impact

Shepherd

Winwood

Venkatraman

et al. 2020

Physica Status Solidi (b)

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Poisson's ratio (ν) is the negative ratio of the lateral-to-axial strain of a material under compression or tension and ranges between À1 and þ0.5 for 3D isotropic materials, according to elasticity theory, [1] and À1 and þ1 for 2D isotropic materials. [2] Auxetic materials (and structures) have a negative Poisson's ratio (NPR) as they expand laterally when stretched and contract laterally when compressed. [3] Auxetics can have enhanced properties including increased resistance to indentation and increased energy absorption under compression. [4,5] They also exhibit synclastic curvature, [3,6] which could improve the conformability of clothing to the body. Such properties make auxetics ideal candidates for enhancing personal protective equipment (PPE) in sport, [7] such as those used in rugby, [8] American football, [9] or snow sports. [10] Head injuries, for example, still frequently occur in sport despite developments in helmet technology and increased user uptake. [11,12] Shear thickening materials are often used in sporting PPE products, such as snowboard back protectors, but their ability to limit impact forces can change with temperature. [13] Approximately 4.5 million people are treated in EU hospitals for sports-related injuries annually, [14] at a cost of €2.4 billion (%£2 billion), [15] which could be reduced with more effective protection and better regulation. Better fitting, more comfortable, and higher-performing auxetic PPE has the potential to increase participation in sport and improve general well-being, both physically and mentally. [16] In addition, a more active population could reduce healthcare costs, particularly as National Health Service providers spent %£900 million on addressing health issues related to physical inactivity in the UK in 2009/2010. [17] There are also social health benefits of practicing a sport with others. [18] Bailly et al. found that snow-sport participants with an injury that was not to the head were less likely to be wearing a helmet than those without an injury, [19] challenging the concerns of Wilson that sporting participants who wear PPE take more risks. [20] Although auxetic systems can be found in nature, [21] research into these materials has typically focused on manmade products like open-cell foam, which was first manufactured by Lakes using thermomechanical techniques that combined compression and heating. [3] Auxetic foam fabrication has also been investigated by Chan and Evans. [4,22] Scarpa et al. were the first to report the dynamic response of auxetic open-cell foam, highlighting its potential in crashworthiness applications. [23] More recently, this potential was demonstrated further; open-cell auxetic foam reduced the peak acceleration of drop tower impacts (energies up to 5.6 J) by two to three times, compared with its conventional

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mentioning

confidence: 99%

Validation of a Finite Element Modeling Process for Auxetic Structures under Impact

Shepherd

Winwood

Venkatraman

et al. 2020

Physica Status Solidi (b)

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“…23,24,25 The NOCASE headform was attached to a Hybrid III neck assembly in this work, despite known deficiencies in side flexion, 26,27 because of its use in the only extant oblique helmet standard 20 and other oblique impact studies. 6 While headform impact response may be different for tests conducted with a different headform, different neck or without a neck, the aim of this work was to characterize the impact surface friction and its influence on headform impact response.…”

Section: Methodsmentioning

confidence: 99%

“…3 Recent works have used two methods to create oblique impacts involving either a normal impact on a flat moving table 4,5 or an oblique impact on a stationary angled surface. 6 However, none of these studies have considered the effect of impact surface roughness. Friction between the scalp and helmet has been measured, 7 but this work was done quasi-statically, and did not consider the roughness of the impact surface.…”

Section: Introductionmentioning

confidence: 99%

The effect of surface roughness on oblique bicycle helmet impact tests

Petersen

Smith

Nevins

2020

Proceedings of the Institution of Mechanical Engineers, Part P:

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The friction between a helmet and impact surface affects the accelerations imparted to the head. The roughness of the impact surface is, therefore, a consideration when developing oblique impact standards. An 80-grit abrasive paper is commonly used in oblique impact tests to simulate a road surface, but has not been validated for bicycle impacts and may not accurately represent real road surfaces. In the following study, a helmeted NOCSAE headform with a Hybrid III neck was dropped onto a 45° anvil at 6.5 m/s using a twin wire guided drop tower. Helmeted drops were performed in two orientations (frontal and side) on road surfaces, roughened steel surfaces, 80-grit abrasive paper and a low friction surface. For each impact, measures of linear and rotational acceleration were obtained. These metrics were compared across impact orientations and surfaces to assess the influence of surface roughness on headform impact response. Frontal impacts were less sensitive to the impact surface roughness than side impacts across metrics. Among metrics, rotational acceleration showed the largest effect due to surface roughness. Compared to the road surface, peak rotational acceleration from impacts on the 80-grit surface were 6.5% less and 48% greater for frontal and side impacts, respectively. Based on consideration of the peak and cumulative impact measures, steel impact surfaces appear to better simulate road impact than the commonly used 80-grit abrasive paper.

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“…12 However, recent advances in helmet design suggest that the effectiveness of helmets may be further improved by targeted mitigation of rotational acceleration of the head. [8][9][10] Brain tissues are highly susceptible to rotational acceleration of the head, which subjects brain tissue to shear forces that can induce diffuse axonal injury. 16,18,22,29 Being incompressible, brain tissue has a high resistance to compressive forces associated with linear acceleration, but a very low resistance to shear forces associated with rotational acceleration.…”

Section: Introductionmentioning

confidence: 99%

Impact Performance Comparison of Advanced Snow Sport Helmets with Dedicated Rotation-Damping Systems

2021

Self Cite

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Rotational acceleration of the head is a principal cause of concussion and traumatic brain injury. Several rotation-damping systems for helmets have been introduced to better protect the brain from rotational forces. But these systems have not been evaluated in snow sport helmets. This study investigated two snow sport helmets with different rotation-damping systems, termed MIPS and WaveCel, in comparison to a standard snow sport helmet without a rotation-damping system. Impact performance was evaluated by vertical drops of a helmeted Hybrid III head and neck onto an oblique anvil. Six impact conditions were tested, comprising two impact speeds of 4.8 and 6.2 m/s, and three impact locations. Helmet performance was quantified in terms of the linear and rotational kinematics, and the predicted probability of concussion. Both rotation-damping systems significantly reduced rotational acceleration under all six impact conditions compared to the standard helmet, but their effect on linear acceleration was less consistent. The highest probability of concussion for the standard helmet was 89%, while helmets with MIPS and WaveCel systems exhibited a maximal probability of concussion of 67 and 7%, respectively. In conclusion, rotation-damping systems of advanced snow sport helmets can significantly reduce rotational head acceleration and the associated concussion risk.

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Evaluation of a novel bicycle helmet concept in oblique impact testing

Cited by 80 publications

References 33 publications

Validation of a Finite Element Modeling Process for Auxetic Structures under Impact

Validation of a Finite Element Modeling Process for Auxetic Structures under Impact

The effect of surface roughness on oblique bicycle helmet impact tests

Impact Performance Comparison of Advanced Snow Sport Helmets with Dedicated Rotation-Damping Systems

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