A multiscale experimental approach to characterize micro-to-macro transition length scale in polymer foams

Koohbor, Behrad; Pagliocca, Nicholas; Youssef, George

doi:10.1016/j.mechmat.2021.104006

Cited by 11 publications

(10 citation statements)

References 48 publications

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“…45 The interplay of multiple scales also determines the structural and dynamic properties of other multiphase polymer materials 46 that are highly heterogeneous and filled by internal interfaces, such as polymer blends, 47,48 block copolymer melts and solutions, 49−52 or foams. 53 It is particularly prominent in polymer nanocomposites, 54−58 where fillers are introduced, e.g., to improve the mechanical properties of a polymeric matrix. The molecular origins of the resulting mechanical reinforcement are diverse, they include a redistribution of strain in the polymer matrix 59 as well as stretching of chains at the interfaces.…”

Section: Introductionmentioning

confidence: 99%

Understanding and Modeling Polymers: The Challenge of Multiple Scales

Schmid

2022

ACS Polym. Au

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Polymer materials are multiscale systems by definition. Already the description of a single macromolecule involves a multitude of scales, and cooperative processes in polymer assemblies are governed by their interplay. Polymers have been among the first materials for which systematic multiscale techniques were developed, yet they continue to present extraordinary challenges for modellers. In this Perspective, we review popular models that are used to describe polymers on different scales and discuss scale-bridging strategies such as static and dynamic coarse-graining methods and multiresolution approaches. We close with a list of hard problems which still need to be solved in order to gain a comprehensive quantitative understanding of polymer systems.

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Section: Introductionmentioning

confidence: 99%

Understanding and Modeling Polymers: The Challenge of Multiple Scales

Schmid

2022

ACS Polym. Au

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“…The assumption of a one-dimensional stress state requires the base materials to possess zero (or at least near zero) Poisson ratios. This requirement was previously verified for the utilized foam materials through in situ experimental measurements whose details can be found elsewhere. , …”

Section: Methodsmentioning

confidence: 82%

“…This requirement was previously verified for the utilized foam materials through in situ experimental measurements whose details can be found elsewhere. 31 , 34 …”

Section: Methodsmentioning

confidence: 99%

“…The present study examines the role of interface adhesive properties on the mechanical response of bilayer density-graded polyurea foam structures. In recent years, polyurea foam has attracted a good amount of interest due to its hierarchical cellular network and semiclosed cellular structure in impact mitigation applications. ,, Polyurea shows an extended plateau area in stress–strain response. , The mechanical characterization of polyurea foams demonstrates a superior characteristic under both quasi-static and dynamic loading conditions. ,, The outstanding mechanical performance of polyurea foam under different loading conditions distinguishes it from other elastomeric cellular solids. , …”

Section: Introductionmentioning

confidence: 99%

“…9 , 32 , 33 The outstanding mechanical performance of polyurea foam under different loading conditions distinguishes it from other elastomeric cellular solids. 31 , 34 …”

Section: Introductionmentioning

confidence: 99%

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Tuning the Mechanical Behavior of Density-Graded Elastomeric Foam Structures via Interlayer Properties

et al. 2022

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The concept of density-graded foams has been proposed to simultaneously enhance strain energy dissipation and the load-bearing capacities at a reduced structural weight. From a practical perspective, the fabrication of density-graded foams is often achieved by stacking different foam densities. Under such conditions, the adhesive interlayer significantly affects the mechanical performance and failure modes of the structure. This work investigates the role of different adhesive layers on the mechanical and energy absorption behaviors of graded flexible foams with distinct density layers. Three adhesive candidates with different chemical, physical, and mechanical characteristics are used to assemble density-graded polyurea foam structures. The mechanical load-bearing and energy absorption performances of the structures are evaluated under quasi-static and dynamic loading conditions. Mechanical tests are accompanied by digital image correlation (DIC) analyses to study the local strain fields developed in the vicinity of the interface. Experimental measurements are also supplemented by model predictions that reveal the interplay between the mechanical properties of an adhesive interlayer and the macroscale mechanical performance of the graded foam structures. The results obtained herein demonstrate that the deformation patterns and macroscale properties of graded foam composites can be tuned by selecting different bonding agents. It is also shown that the proper selection of an adhesive can be a practical way to address the strength–energy dissipation dichotomy in graded structures.

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Density‐Dependent Impact Resilience and Auxeticity of Elastomeric Polyurea Foams

et al. 2022

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This research investigates the dynamic response of a novel polyurea foam with different densities by separately submitting samples to single and multiple impacts at different energies ranging from 1.77 to 7.09 J. The impact and transmitted force‐time histories are acquired during the impact events. Deformation of the samples is also recorded using high‐speed photography and analyzed using digital image correlation (DIC) to characterize density‐dependent strain rate and Poisson's ratio. The analyses of the force‐time histories highlight the interrelationship between the incoming impact energy and force characteristics, including amplitude and durations. The experimental results reveal that polyurea foams can absorb nearly 50% of the incoming impact energy irrespective of their density. The dynamic impact efficacy of the foam persists even after sequential impact events are imparted on the same samples, with only a 20% drop in the load‐bearing capacity after seven consecutive impacts. Furthermore, as verified via electron microscopy observations, the higher‐density foam does not exhibit any permanent damage. This high‐density polyurea foam shows reversible auxetic transition at all impact energies considered herein. The outcomes of this research indicate the suitability of polyurea foams for cushioning and impact mitigation applications, especially in repeated biomechanical impact scenarios.

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A multiscale experimental approach to characterize micro-to-macro transition length scale in polymer foams

Cited by 11 publications

References 48 publications

Understanding and Modeling Polymers: The Challenge of Multiple Scales

Understanding and Modeling Polymers: The Challenge of Multiple Scales

Tuning the Mechanical Behavior of Density-Graded Elastomeric Foam Structures via Interlayer Properties

Density‐Dependent Impact Resilience and Auxeticity of Elastomeric Polyurea Foams

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