Freestanding loadbearing structures with Z-shaped particles

Murphy, Kieran; Reiser, Nikolaj; Choksy, Darius; Singer, Clare E.; Jaeger, Heinrich M.

doi:10.1007/s10035-015-0600-2

Cited by 44 publications

(52 citation statements)

References 32 publications

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“…This picture fails at some point for more exotic grain shape. For extended particles with kinks, random packing causes interpenetration and entanglement, which complicate the stability condition by non-trivially coupling torques and normal contacts 27,39 . For spheres, torques are mediated only by friction, but hooked particles must both rotate and translate in order to flow past each other.…”

Section: Internal Stresses and Boundary Effectsmentioning

confidence: 99%

Mechanics of randomly packed filaments—The “bird nest” as meta-material

Weiner

Bhosale

Gazzola

et al. 2020

Journal of Applied Physics

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Systems of randomly packed, macroscopic elements, from jammed spherical grains to tangled long filaments, represent a broad class of disordered meta-materials with a wide range of applications and manifestations in nature. A 'bird nest' presents itself at an interface between hard round grains described by granular physics to long soft filaments, the center of textile material science. All of these randomly packed systems exhibit forms of self assembly, evident through their robust packing statistics, and a common, unusual elastoplastic response to oedometric compression. In reviewing packing statistics, mechanical response characterization and consideration of boundary effects, we present a perspective that attempts to establish a link between the bulk and local behaviour of a pile of sand and a wad of cotton, demonstrating the nest's relationship with each. Finally, potential directions for impactful applications are outlined.

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Section: Internal Stresses and Boundary Effectsmentioning

confidence: 99%

Mechanics of randomly packed filaments—The “bird nest” as meta-material

Weiner

Bhosale

Gazzola

et al. 2020

Journal of Applied Physics

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“…Shape also determines the resistance particles experience toward reconfiguring along rotational and translational degrees of freedom. As a result, particle shape greatly affects the bulk properties of granular materials [1,2,3,4]. Aggregates of angular particles have higher shear strength than those of rounded particles [5,6,7], and platy particles tend to plastically deform with larger stress fluctuations than compact shapes [8].…”

mentioning

confidence: 99%

The intertwined roles of particle shape and surface roughness in controlling the shear strength of a granular material

Murphy

Roth

et al. 2019

Granular Matter

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Both the shape of individual particles and their surface properties contribute to the strength of a granular material under shear. Here we show the degree to which these two aspects can be intertwined. In experiments on assemblies of 3D printed, convex lens-shaped particles, we measure the stress-strain response under repeated compressive loading and find that the aggregate's shear strength falls rapidly when compared to other particle shapes. We probe the granular material at mm-scales with X-ray computed tomography and µmscales with high-resolution surface metrology to look for the cause of the degradation. We find that wear due to accumulated deformation smooths out the lens surfaces in a controlled and systematic manner that correlates with a significant loss of shear strength observed for the assembly as a whole. The sensitivity of lenses to changes in surface properties contrasts with results for assemblies of 3D printed tetrahedra and spheres, which under the same load cycling are found to exhibit only minor degradation in strength. This case study provides insight into the relationship between particle shape, surface wear, and the overall material response, and suggests new strategies when designing a granular material with desired evolution of properties under repeated deformation.

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“…The mechanical stability of rod aggregates is thus intimately related only to the packing [7] and the solid friction [8] at the contact points. Further works have been devoted to the mechanics of assemblies made of more complex objects, such as stars [9], or U-and Z-shaped particles [10,11]. In those cases, in contrast to rods, it is considered that topological constraints are the key ingredient for the observed increase in rigidity.Apart from using rods or rigid non-convex objects, a third approach to produce cohesive assemblies from non-interacting elements is to aggregate soft slender objects, such as fibers [12][13][14] or granular chains [15].…”

mentioning

confidence: 99%

Emergent Strain Stiffening in Interlocked Granular Chains

et al. 2018

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Granular chain packings exhibit a striking emergent strain-stiffening behavior despite the individual looseness of the constitutive chains. Using indentation experiments on such assemblies, we measure an exponential increase in the collective resistance force F with the indentation depth z and with the square root of the number N of beads per chain. These two observations are, respectively, reminiscent of the self-amplification of friction in a capstan or in interleaved books, as well as the physics of polymers. The experimental data are well captured by a novel model based on these two ingredients. Specifically, the resistance force is found to vary according to the universal relation logF∼μsqrt[N]Φ^{11/8}z/b, where μ is the friction coefficient between two elementary beads, b is their size, and Φ is the volume fraction of chain beads when semidiluted in a surrounding medium of unconnected beads. Our study suggests that theories normally confined to the realm of polymer physics at a molecular level can be used to explain phenomena at a macroscopic level. This class of systems enables the study of friction in complex assemblies, with practical implications for the design of new materials, the textile industry, and biology.

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Freestanding loadbearing structures with Z-shaped particles

Cited by 44 publications

References 32 publications

Mechanics of randomly packed filaments—The “bird nest” as meta-material

Mechanics of randomly packed filaments—The “bird nest” as meta-material

The intertwined roles of particle shape and surface roughness in controlling the shear strength of a granular material

Emergent Strain Stiffening in Interlocked Granular Chains

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