Review of Auxetic Materials for Sports Applications: Expanding Options in Comfort and Protection (original) (raw)
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The Application of Auxetic Material for Protective Sports Apparel
Proceedings
Current research of auxetic materials highlights its potential as personal protective equipment for sports apparel with enhanced properties such as conformability, superior energy absorption and reduced thickness. In contrast, commercially available protective materials have proven to be problematic in that they inhibit movement, breathability, wicking and that molded pads are prone to saddling. Foam components are embedded within personal protective equipment for sports apparel, where protective material is positioned at regions of the body frequently exposed to injury of the soft tissue through collision, falls or hard impact. At present, the impact resistance of auxetic open cell polyurethane foam and some additively manufactured auxetic structures have been established, and processes for manufacturing curved auxetic materials as well as molding methods have been developed. Despite this, auxetic materials have not yet been applied as personal protective equipment for sports apparel in current research. This paper argues that there is scope to investigate auxetic materials potential for enhanced wearer functionality through properties of synclastic curvature and biaxial expansion.
Auxetic Materials for Sports Applications
Procedia Engineering, 2014
In this paper, the auxetic effect is introduced, the range of auxetic materials is briefly reviewed, and research demonstrating benefits having potential in sports applications is highlighted. These include the use of auxetic materials in impact protector devices (pads, gloves, helmets and mats) exploiting better conformability for comfort and support, and enhanced energy absorption for lighter and/or thinner components. FE simulations are reported for a new type of auxetic honeycomb having potential in helmet applications, along with indentation testing of auxetic and non-auxetic foams for assessment in protective pads and running shoes applications, for example.
Application of Auxetic Foam in Sports Helmets
Applied Sciences
Auxetic open cell foam was used as the comfort layer within a sports helmet and has been shown to reduce the severity of linear impacts. The work undertaken highlights the potential to further develop auxetic open cell foam as comfort layer and create more effective sporting protective equipment to reduce transmitted linear as well as rotational accelerations during an impact.
2018
Foams are commonly used for cushioning in protective sporting equipment. Volumetrically compressing open-cell polyurethane foam buckles cell ribs creating a re-entrant structure—set by heating then cooling—which can impart auxetic behaviour. Theoretically, auxetic materials improve impact protection by increasing indentation resistance and energy absorption, potentially reducing sporting injuries and burdens on individuals, health services and national economies. In previous work, auxetic foam exhibited ~3 to ~8 times lower peak force (compared to its conventional counterpart) under impacts adopted from tests used to certify protective sporting equipment. Increases to the foam’s density and changes to stress/strain relationships (from fabrication) mean Poisson’s ratio’s contribution to reduced peak forces under impact is unclear. This work presents a simple fabrication method for foam samples with comparable density and linear stress/strain relationship, but different Poisson’s rati...
Auxetic Foam for Snow-Sport Safety Devices
Snow Sports Trauma and Safety, 2017
Skiing and snowboarding are popular snow-sports with inherent risk of injury. There is potential to reduce the prevalence of injuries by improving and implementing snow-sport safety devices with the application of advanced materials. This chapter investigates the application of auxetic foam to snow-sport safety devices. Composite pads-consisting of foam covered with a semi-rigid shell-were investigated as a simple model of body armour and a large 70 × 355 × 355 mm auxetic foam sample was fabricated as an example crash barrier. The thermo-mechanical conversion process was applied to convert open-cell polyurethane foam to auxetic foam. The composite pad with auxetic foam absorbed around three times more energy than the conventional equivalent under quasi-static compression with a concentrated load, indicating potential for body armour applications. An adapted thermo-mechanical process-utilising through-thickness rods to control in-plane compression-was applied to fabricate the large sample with relatively consistent properties throughout, indicating further potential for fabrication of a full size auxetic crash barrier. Further work will create full size prototypes of snow-sport safety devices with comparative testing against current products.