Mechanical ageing performance of minimalist and traditional footwear foams

Lippa, Nadine M.; Collins, Paul K.; Bonacci, Jason; Piland, Scott G.; Rawlins, James W.; Gould, Trenton E.

doi:10.1080/19424280.2016.1228702

Cited by 14 publications

(24 citation statements)

References 41 publications

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“…Certain differences in compressive behavior for each shoe-region combination were attributed to initial midsole foam thickness. 14 For example, TS and heel underwent more displacement and absorbed more energy than MS and forefoot on average because the thicker foams were more compliant (Figure 6), which resulted in a less aggressive loading rate, greater deformation, and larger hysteresis area (Figures 3, 5 and 6).…”

Section: Discussionmentioning

confidence: 99%

“…The stride length and force-time profile were then used to calculate the number of impacts needed to age the shoes for 42 km. A marathon distance was chosen for the study because measurable midsole degradation was shown to occur within this distance, 14 and it is a standard distance for an athlete to run continuously.…”

Section: Methodsmentioning

confidence: 99%

“…In general, mechanical aging (MA) of midsoles has revealed that EVA foam thickness affects inherent energy absorption capability, with thick, compliant foam absorbing more energy overall, but degrading at a faster rate than thinner, stiff foam. 14 Additional work is required to determine whether decreased drop, decreased energy absorption, and altered running gait occur in a more biofidelic degradation of the midsole with realistic forces applied for each shoe-region condition. It may be anticipated that important interactions among shoe type, midsole degradation, and runner biomechanics may occur.…”

Section: Introductionmentioning

confidence: 99%

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Effect of mechanically aged minimalist and traditional footwear on female running biomechanics

Lippa

Bonacci

Collins

et al. 2019

Proceedings of the IMechE

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The purpose of this study was to improve the understanding of human–material interactions by combining polymer engineering and biomechanical approaches. The forefoot and heel of traditional shoes and minimalist running shoes were degraded using a mechanical aging protocol to quantify (1) the effect of subject-specific degradation and (2) human biomechanical effects due to decreased material properties. Four recreational-level female participants ran in the shoes pre-mechanical aging to determine the aging protocol input parameters and post-mechanical aging to evaluate the effect of degradation on kinematics and kinetics. Initial biomechanics translated into different mechanical aging input parameters among conditions: 500 greater number of impact cycles for minimalist shoe, 430 N higher peak force for forefoot, 75 kPa greater peak stress for the heel, 3.1 and 13.7 kN/s greater loading rates for minimalist shoe and the heel, and recovery time 220 ms greater for the heel. From mechanical aging, the shoe types and regions lost 1.2–1.8 mm thickness and 38%–54% energy absorption overall, while drop decreased 0.6 mm for traditional shoe only. Samples degraded at different rates depending on runner-specific input parameters. Human kinematics and kinetics were affected by both shoe type and aging. Aging of the shoes decreased knee flexion velocity (1°/s; p = 0.01), decreased ankle dorsiflexion during stance (3°, p = 0.01), and increased the vertical loading rate (4 BW/s, p = 0.01). The results support previous findings that different footwear influence running biomechanics and concurrently advance footwear science to show running biomechanics are also influenced by shoe degradation rates, such that unique and intuitive human–material interactions are apparent.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effect of mechanically aged minimalist and traditional footwear on female running biomechanics

Lippa

Bonacci

Collins

et al. 2019

Proceedings of the IMechE

Self Cite

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“…Allen et al [105] highlight the potential for auxetic foam to be applied to snow sport safety devices, and this paper could assist with teaching material fundamentals, such as stress, strain and Poisson's ratio. Recent work by Lippa et al [106,107] demonstrates how to mechanically age running shoes and assess degradation.…”

Section: Sport Safetymentioning

confidence: 99%

Resources for sports engineering education

Allen

Goff

2017

Sports Eng

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This paper serves as a resource guide for Sports Engineering educators. The paper covers key topics in Sports Engineering, including ball impact, friction, safety and materials. A variety of resource types are presented to reflect modern methods of learning and searching for information, including textbooks, research and review papers, websites and videos. The field could benefit from more resources specifically designated for teaching Sports Engineering, particularly textbooks.

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“…Physical properties of moldings made from EVA, TPU and SEBS.the quick snapback upon unloading the footstrike[57]. Conventional foams (such as EVA, TPU, etc.)…”

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confidence: 99%

A developed, eco-friendly, and flexible thermoplastic elastomeric foam from SEBS for footwear application

Zhang¹,

Dai²,

Zou³

et al. 2019

Express Polym. Lett.

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In search of new materials to develop comfortable shoe sole, nowadays the researchers have resorted to the thermoplastic elastomers (TPEs) usually used as cushioning materials for its easy processability and adorable physical properties that can meet both the comfort as well as other functional requirements (i.e. fashion, ultralight, aging, etc.). TPEs are a class of copolymers or physical mixes of polymers and have the morphology of non-miscible blends of elastomer and thermoplastic matrix simultaneously. Low or room temperature elastomeric behavior and high temperature processablitiy makes TPE as a suitable material for developing lightweight and recyclable microcellular foams [1]. Most of the commercial TPE foams for footwear application are developed either from thermoplastic polyurethane (TPU) or ethylenevinyl acetate (EVA) copolymer in which the soft matrix provides sufficient free space for gas absorption whereas the rigid matrix prevents the gas diffusion during foaming process [2][3][4][5][6]. Styrene-(ethylene-cobutylene)-styrene polymers (SEBS) derived from the hydrogenation of styrene-butadiene-styrene (SES) polymers is a typical TPE which shows a better weather resistance, lower compression set, lower density, etc., can be a potential alternative of TPU or EVA [7,8]. SEBS consists of a soft midblock of ethylene-butylene (E-co-B) and hard end-blocks of 948 Abstract. Developing eco-friendly, flexible thermoplastic elastomeric foams based on poly(styrene-(ethylene-co-butylene)styrene) (SEBS) is a challenging task because of its poor melt strength. A promising approach to overcome this challenge is the use of synergistic technologies, such as combination of irradiation, supercritical fluid foaming, and steam-chest molding technologies. Herein, foamed beads were produced from pre-crosslinked SEBS beads using supercritical nitrogen as blowing agent, followed by subsequently efficient steam-chest molding to obtain midsole part. The crosslinking was accomplished under the assistance of electron beam. The rheology properties and foaming behavior reveals that the viscosity and modulus of the matrix increase with the increase of crosslinking resulting from increasing the irradiation dose (ID). With increasing the ID, successful foaming with larger expansion and improved cell morphology was achieved. SEBS bead foams were successfully obtained from 65 kGy-derived pre-crosslinked beads through steam-chest molding which showed a specific gravity of 0.252 g·cm -3 and comparable/superior mechanical properties to/than that of commercial thermoplastic polyurethane (TPU) or ethylene-vinyl acetate copolymer (EVA) foams. Especially, the higher elasticity and resilience of SEBS foams meet well the desirable properties for footwear application which supports SEBS to be an alternative for TPU or EVA.

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Mechanical ageing performance of minimalist and traditional footwear foams

Cited by 14 publications

References 41 publications

Effect of mechanically aged minimalist and traditional footwear on female running biomechanics

Effect of mechanically aged minimalist and traditional footwear on female running biomechanics

Resources for sports engineering education

A developed, eco-friendly, and flexible thermoplastic elastomeric foam from SEBS for footwear application

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