Gradient optimization of multi-layered density-graded foam laminates for footwear material design

Uddin, Kazi Zahir; Youssef, George; Trkov, Mitja; Seyyedhosseinzadeh, Hamid; Koohbor, Behrad

doi:10.1016/j.jbiomech.2020.109950

Cited by 40 publications

(29 citation statements)

References 43 publications

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“…Over the range of investigated load application regions, only two buckling modes are observed, those starting at 2α = 16 deg and 2α = 23 deg, which is mechanistically consistent with the results of the considered boundary conditions and shown experimentally by Shorter et al [7]. Such elastic deformation is highly desirable in polymeric foams because (1) it signifies recoverable deformation where the foam padding can sustain repeated loading (recently demonstrated experimentally by our group [13]), and (2) it implies large energy dissipation due to buckling to shunt the energy protecting human brains from a concussion in biomechanical impact scenarios [14].…”

Section: Effect Of Microcell Wallsupporting

confidence: 87%

Mechanics of Microspheres Reinforced Hollow Microcells

Youssef

Nacy

Huynh

2021

Journal of Applied Mechanics

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Emerging polymeric foams exhibiting unique microstructure of microspherical shells with reinforcing dense microspheres creates a new opportunity for impact-tolerant foam paddings in sport gears applications. This paper describes the static response of reinforced microcell consisting of an outer spherical shell and uniformly distributed microspheres while quantifying the stiffening effect. The distribution of the microspheres is illustrated using the Fourier series, allowing tuning of the reinforcing strategy. Expressions of the external and internal works are derived, whereas the Ritz energy method is adopted to calculate the deformations due to a compressive load distributed over a range of areas. Emphasis is given to the effect of the geometrical attributes of the microcell and the reinforcing microspheres on the resulting deformation response and stiffening effect. The framework is used to investigate the response of several case studies to elucidate the effects of relative radii ratio, reinforcement density, microcell wall thickness, and loading configurations on the stiffness. A new normalized strain energy parameter is introduced to simplify and accelerate the analysis while providing insights on the underpinnings of the observed buckling response. The results strongly suggest the viability of the newly discovered foam microstructure in managing static loads while providing an opportunity to strategically tune the mechanical response using the analytical framework presented herein.

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Section: Effect Of Microcell Wallsupporting

confidence: 87%

Mechanics of Microspheres Reinforced Hollow Microcells

Youssef

Nacy

Huynh

2021

Journal of Applied Mechanics

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“…Polyurea foams have been proposed for multiple applications, including football helmets, footwear products, and body armors. [ 11–13 ] It was found that polyurea foam with a density of 98 kg m −3 reduced the peak acceleration and severity index by 22% and 25%, respectively, compared to vinyl nitride foam used as a liner for football helmets. [ 12 ] The high performance of polyurea foam persisted at a range of temperatures between −15 and 50 °C.…”

Section: Introductionmentioning

confidence: 99%

Characterization of Energy Absorption and Strain Rate Sensitivity of a Novel Elastomeric Polyurea Foam

et al. 2020

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Elastomeric polymer foams are widely used in sports and other protective padding applications due to their unique properties, such as excellent cushioning and relatively high‐energy absorption to weight ratio. This work investigates the mechanical and energy absorption performance of an elastomeric hybrid structure polyurea foam in response to low‐velocity impact. The examined polyurea foams are synthesized using a novel self‐foaming process that leads to the development of a semi‐closed cellular structure. The quasi‐static response of the foam is first characterized by measuring the global stress–strain and energy absorption characteristics. The evolution of the foam's Poisson's ratio is also characterized by in situ digital image correlation (DIC) measurements. The same properties are also studied in dynamic loading conditions by subjecting the foam samples to controlled impact tests. A strain‐dependent rate sensitivity parameter is used to quantify differences between the quasi‐static and dynamic strength and energy absorption responses of the foam. The examined foam shows significant enhancement in strength at increased strain rates while retaining its excellent energy absorption capacity. This unique characteristic of the examined foam is discussed in terms of the concurrent effects of entrapped gas and the rate sensitivity of the parent polymer.

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“…[12][13][14][15][16] Property improvement has been observed in impact and static flexural loading. 10,[17][18][19] For instance, Uddin and coworkers proved that significant improvement in strength and energy absorption performance can be achieved through density gradation of polyurea foams in footwear design. 17 Polit and coworkers investigated the static bending and buckling response of nanocomposites foams, showing that the design of the localized additive loading and of porosity (both in symmetric and asymmetric configuration) can significantly affect mechanical performance.…”

Section: Introductionmentioning

confidence: 99%

“…10,[17][18][19] For instance, Uddin and coworkers proved that significant improvement in strength and energy absorption performance can be achieved through density gradation of polyurea foams in footwear design. 17 Polit and coworkers investigated the static bending and buckling response of nanocomposites foams, showing that the design of the localized additive loading and of porosity (both in symmetric and asymmetric configuration) can significantly affect mechanical performance. 18 Kazemi utilized a uniform as well as layered polyurethane foams in sandwich structures showing that the arrangement of the layers induced a 7-fold increase of energy absorption capacity of a layered foam with respect to a uniform foam with equal average density.…”

Section: Introductionmentioning

confidence: 99%

Sintering graded foamed beads: Compressive properties

Errichiello¹,

Cammarano²,

Maio

et al. 2021

J of Applied Polymer Sci

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Designing the foam structures in terms of density and morphology gives the chance to tune their mechanical and functional properties to the specific application. Nowadays, this design has been leveled up by the introduction of graded foams which are characterized by spatially nonuniform densities and/or morphologies. Graded foams have proved superior compared to uniform one in numerous examples and loading conditions but in pure compressive loading, where properties such as the Young's modulus of graded foams are always inferior to uniform ones. When using sintered beads foams, macroscopic pure compression may induce local bending on the single bead, which can be exploited to induce stiffening. This thesis was investigated on both polystyrene and thermoplastic polyurethane samples made by foamed beads sintered in a cylindrical mold. The response to compressive tests of graded foams made by sintering beads having nonuniform cells structures was compared to the uniform counterparts. The results evidenced that, at same average density, foams had up to a 30% ca. of increase of the Young's modulus when the beads are characterized by a denser outer layer.

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Gradient optimization of multi-layered density-graded foam laminates for footwear material design

Cited by 40 publications

References 43 publications

Mechanics of Microspheres Reinforced Hollow Microcells

Mechanics of Microspheres Reinforced Hollow Microcells

Characterization of Energy Absorption and Strain Rate Sensitivity of a Novel Elastomeric Polyurea Foam

Sintering graded foamed beads: Compressive properties

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