Swelling of cellular solids: From conventional to re-entrant honeycombs

Rafsanjani, Ahmad; Derome, Dominique; Guyer, R. A.; Carmeliet, Jan

doi:10.1063/1.4807844

Cited by 6 publications

(4 citation statements)

References 22 publications

(21 reference statements)

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“…Based on this hypothetical explanation, the complex hierarchical structure of wood enhances the dimensional stability of wood across scales from cell wall substance to cellular tissue and to macroscopic scales. These observations are in the same direction as recent findings in our own micromechanics investigations that show the anisotropic swelling behaviour of cellular materials is essentially due to the swelling anisotropy of the cell wall material [31,32]. Reported values in the literature for in situ swelling or shrinkage of latewood cell walls of softwoods obtained by microscopic observations are comparable to our measurements.…”

Section: Discussionsupporting

confidence: 92%

Hygroscopic swelling and shrinkage of latewood cell wall micropillars reveal ultrastructural anisotropy

Rafsanjani

Stiefel

Jefimovs

et al. 2014

J. R. Soc. Interface.

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We document the hygroscopic swelling and shrinkage of the central and the thickest secondary cell wall layer of wood (named S2) in response to changes in environmental humidity using synchrotron radiation-based phase contrast X-ray tomographic nanoscopy. The S2 layer is a natural fibre-reinforced nanocomposite polymer and is strongly reactive to water. Using focused ion beam, micropillars with a cross section of few micrometres are fabricated from the S2 layer of the latewood cell walls of Norway spruce softwood. The thin neighbouring cell wall layers are removed to prevent hindering or restraining of moisture-induced deformation during swelling or shrinkage. The proposed experiment intended to get further insights into the microscopic origin of the anisotropic hygro-expansion of wood. It is found that the swelling/shrinkage strains are highly anisotropic in the transverse plane of the cell wall, larger in the normal than in the direction parallel to the cell wall's thickness. This ultrastructural anisotropy may be due to the concentric lamellation of the cellulose microfibrils as the role of the cellulose microfibril angle in the transverse swelling anisotropy is negligible. The volumetric swelling of the cell wall material is found to be substantially larger than the one of wood tissues within the growth ring and wood samples made of several growth rings. The hierarchical configuration in wood optimally increases its dimensional stability in response to a humid environment with higher scales of complexity.

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Section: Discussionsupporting

confidence: 92%

Hygroscopic swelling and shrinkage of latewood cell wall micropillars reveal ultrastructural anisotropy

Rafsanjani

Stiefel

Jefimovs

et al. 2014

J. R. Soc. Interface.

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“…Studies based on computational mechanical modeling have also shown that the geometry of the cell walls and the cell wall layered structure can play a role in the anisotropic swelling of a cellular solid. Honeycomb cellular solids with homogenous cell walls swell isotropically, while honeycombs with a layered cell wall structure displayed anisotropic swelling behavior [107,108].…”

Section: Cellular Structurementioning

confidence: 99%

Wood Moisture-Induced Swelling at the Cellular Scale—Ab Intra

Arzola-Villegas

Lakes

Plaza

et al. 2019

Forests

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Wood, a complex hierarchical material, continues to be widely used as a resource to meet humankind’s material needs, in addition to providing inspiration for the development of new biomimetic materials. However, for wood to meet its full potential, researchers must overcome the challenge of understanding its fundamental moisture-related properties across its many levels of hierarchy spanning from the molecular scale up to the bulk wood level. In this perspective, a review of recent research on wood moisture-induced swelling and shrinking is presented from the molecular level to the cellular scale. Numerous aspects of swelling and shrinking in wood remain poorly understood, sub-cellular phenomena in particular, because it can be difficult to study them experimentally. Here, we discuss recent research endeavors at each of the relevant length scales, including the molecular, cellulose elementary fibril, secondary cell wall layer nanostructure, cell wall, cell, and cellular levels. At each length scale, we provide a discussion on the current knowledge and suggestions for future research. The potential impacts of moisture-induced swelling pressures on experimental observations of swelling and shrinking in wood at different length scales are also recognized and discussed.

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“…Other studies [32,33] are concerned with the effect of a turgor pressure on the effective stiffness of foam solids like the parenchyma tissue, but their scope limits to isotropically shaped cells in the stretching-dominated regime. Some studies have investigated the influence of cell shape on the overall expansion of honeycombs, however, these considered only a small orthotropic expansion of the honeycomb walls rather than an internal pressurization [34]. No explicit investigation of microscopic swelling deformation at less than fully turgid pressures has been provided.…”

Section: Introductionmentioning

confidence: 99%

Pressurized honeycombs as soft-actuators: a theoretical study

Guiducci

Fratzl

Bréchet

et al. 2014

J. R. Soc. Interface.

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The seed capsule of Delosperma nakurense is a remarkable example of a natural hygromorph, which unfolds its protecting valves upon wetting to expose its seeds. The beautiful mechanism responsible for this motion is generated by a specialized organ based on an anisotropic cellular tissue filled with a highly swelling material. Inspired by this system, we study the mechanics of a diamond honeycomb internally pressurized by a fluid phase. Numerical homogenization by means of iterative finite-element (FE) simulations is adapted to the case of cellular materials filled with a variable pressure fluid phase. Like its biological counterpart, it is shown that the material architecture controls and guides the otherwise unspecific isotropic expansion of the fluid. Deformations up to twice the original dimensions can be achieved by simply setting the value of input pressure. In turn, these deformations cause a marked change of the honeycomb geometry and hence promote a stiffening of the material along the weak direction. To understand the mechanism further, we also developed a micromechanical model based on the Born model for crystal elasticity to find an explicit relation between honeycomb geometry, swelling eigenstrains and elastic properties. The micromechanical model is in good qualitative agreement with the FE simulations. Moreover, we also provide the force-stroke characteristics of a soft actuator based on the pressurized anisotropic honeycomb and show how the internal pressure has a nonlinear effect which can result in negative values of the in-plane Poisson's ratio. As nature shows in the case of the D. nakurense seed capsule, cellular materials can be used not only as low-weight structural materials, but also as simple but convenient actuating materials.

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Swelling of cellular solids: From conventional to re-entrant honeycombs

Cited by 6 publications

References 22 publications

Hygroscopic swelling and shrinkage of latewood cell wall micropillars reveal ultrastructural anisotropy

Hygroscopic swelling and shrinkage of latewood cell wall micropillars reveal ultrastructural anisotropy

Wood Moisture-Induced Swelling at the Cellular Scale—Ab Intra

Pressurized honeycombs as soft-actuators: a theoretical study

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