Microscopic and macroscopic instabilities in elastomeric foams

Luan, Shengzhi; Kraynik, Andrew M.; Gaitanaros, Stavros

doi:10.1016/j.mechmat.2021.104124

Cited by 9 publications

(4 citation statements)

References 57 publications

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“…While native cartilage shares a similar vertical alignment, the associated length scales are much smaller, with collagen fiber sizes of ∼ 100nm, a feature that could alter the resulting mechanical behavior. Typically, in low-density lattices and porous materials under compression, localization leads to bands of collapsed pores forming at a certain slope with respect to the loading surface (18). Contrary, in this work the collapsing pores form peripherally and divide the scaffold in highly deformed pore clusters near the free boundary, and much less distorted regions in the interior of the specimen.…”

Section: Discussionmentioning

confidence: 99%

“…The associated deformations for a 40% nominal strain are shown in Figure 5(b). Even though many soft cellular materials, including elastomeric foams (18) and 3D-printed porous media (19), show negligible expansion in the transverse direction when compressed, the strong area reduction that the collagen scaffolds display, corresponding to a negative tangent Poisson's ratio, is a characteristic seen in a certain class of mechanical metamaterials (20)(21)(22) and is often associated with improved energy absorption characteristics.…”

Section: R a F Tmentioning

confidence: 99%

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3D in-situ characterization reveals the instability-induced auxetic behavior of collagen scaffolds for tissue engineering

Chen,

Kim,

Bouklas

et al. 2024

Preprint

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Collagen scaffolds seeded with human chondrocytes have shown great potential for cartilage repair and regeneration. However, these porous scaffolds buckle under low compressive forces, creating regions of highly localized deformations that can cause cell death and deteriorate the integrity of the engineered tissue. We perform three-dimensional (3D) tomography-based characterization to track the evolution of collagen scaffolds’ microstructure under large deformation. The results illustrate how instabilities produce a spatially varying compaction across the specimens, with more pronounced collapse near the free boundaries. We discover that, independent of differences in pore-size distributions, all collagen scaffolds examined displayed strong auxetic behavior i.e., their transverse area contracts under compression, as a result of the instability cascade. This feature, typically characteristic of engineered metamaterials, is of critical importance for the performance of collagen scaffolds in tissue engineering, especially regarding the persistent challenge of lateral integration in cartilage constructs.

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Section: Discussionmentioning

confidence: 99%

Section: R a F Tmentioning

confidence: 99%

3D in-situ characterization reveals the instability-induced auxetic behavior of collagen scaffolds for tissue engineering

Chen,

Kim,

Bouklas

et al. 2024

Preprint

Self Cite

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“…Studies have shown that the cell size of elastomeric foams is typically between one hundred microns and one millimeter, and the larger the cell, the less homogeneous the foam [1,30]. Since we used uniform cell size distribution to represent monodisperse foam [31], a structure size of 2 × 2 × 2 mm 3 and a voxel length of 10 µm were chosen to allow the model to include the largest cell possible while saving computation time and resources. Then, the cell size range was set to 100~500 µm.…”

Section: Design Space Definitionmentioning

confidence: 99%

Utilizing ANN for Predicting the Cauchy Stress and Lateral Stretch of Random Elastomeric Foams under Uniaxial Loading

et al. 2023

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As a result of their cell structures, elastomeric foams exhibit high compressibility and are frequently used as buffer cushions in energy absorption. Foam pads between two surfaces typically withstand uniaxial loads. In this paper, we considered the effects of porosity and cell size on the mechanical behavior of random elastomeric foams, and proposed a constitutive model based on an artificial neural network (ANN). Uniform cell size distribution was used to represent monodisperse foam. The constitutive relationship between Cauchy stress and the four input variables of axial stretch λU, lateral stretch λL, porosity φ, and cell size θ was given by con-ANN. The mechanical responses of 500 different foam structures (20% < φ < 60%, 0.1 mm < θ < 0.5 mm) under compression and tension loads (0.4 < λU < 3) were simulated, and a dataset containing 100,000 samples was constructed. We also introduced a pre-ANN to predict lateral stretch to address the issue of missing lateral strain data in practical applications. By combining physical experience, we chose appropriate input forms and activation functions to improve ANN’s extrapolation capability. The results showed that pre-ANN and con-ANN could provide reasonable predictions for λU outside the dataset. We can obtain accurate lateral stretch and axial stress predictions from two ANNs. The porosity affects the stress and λL, while the cell size only affects the stress during foam compression.

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“…In brittle polymers, fracture of ligaments occurs before or immediately after elastic instabilities following the peak-stress (Thornton and Magee, 1975;Ashby and Gibson, 1997;Triantafillou and Gibson, 1990;Bi et al, 2020). In turn, the recent study of Luan et al (2022) has focused on the compressive response of flexible elastomers, where the effect of smoothness of the intervoid ligaments and polydispersity of void size has been addressed numerically. Therein, those two geometrical characteristics were shown to affect both the initial stiffness of foams (which is in qualitative agreement with the experimental work of Zerhouni et al (2019)) as well as the level of the peak-stress.…”

Section: Introductionmentioning

confidence: 99%

Mechanically-grown morphogenesis of Voronoi-type materials: Computer design, 3D-printing and experiments

Hooshmand-Ahoor

Tarantino

Danas

2022

Mechanics of Materials

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Microscopic and macroscopic instabilities in elastomeric foams

Cited by 9 publications

References 57 publications

3D in-situ characterization reveals the instability-induced auxetic behavior of collagen scaffolds for tissue engineering

3D in-situ characterization reveals the instability-induced auxetic behavior of collagen scaffolds for tissue engineering

Utilizing ANN for Predicting the Cauchy Stress and Lateral Stretch of Random Elastomeric Foams under Uniaxial Loading

Mechanically-grown morphogenesis of Voronoi-type materials: Computer design, 3D-printing and experiments

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