Experimental micromechanical characterisation of wood cell walls

Eder, Michaela; Arnould, Olivier; Dunlop, John W. C.; Hornatowska, Joanna; Salmén, Lennart

doi:10.1007/s00226-012-0515-6

Cited by 124 publications

(104 citation statements)

References 90 publications

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“…This underestimation is due to anisotropy in the cell wall; contact experiments, by their design, measure a combination of the transverse and axial properties. The reduced modulus of wood cell wall has been found to depend on the anisotropic elastic constants [22,23]. The transverse fibre Young's modulus of bamboo is likely substantially less than the axial value, as is the case in wood, where, for example, the transverse and axial moduli for the solid cell wall are 10 and 35 GPa, respectively [24].…”

Section: Mechanical Test Resultsmentioning

confidence: 99%

The structure and mechanics of Moso bamboo material

Dixon

Gibson

2014

J. R. Soc. Interface.

281

152

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Although bamboo has been used structurally for millennia, there is currently increasing interest in the development of renewable and sustainable structural bamboo products (SBPs). These SBPs are analogous to wood products such as plywood, oriented strand board and glue-laminated wood. In this study, the properties of natural Moso bamboo (Phyllostachys pubescens) are investigated to further enable the processing and design of SBPs. The radial and longitudinal density gradients in bamboo give rise to variations in the mechanical properties. Here, we measure the flexural properties of Moso bamboo in the axial direction, along with the compressive strengths in the axial and transverse directions. Based on the microstructural variations (observed with scanning electron microscopy) and extrapolated solid cell wall properties of bamboo, we develop models, which describe the experimental results well. Compared to common North American construction woods loaded along the axial direction, Moso bamboo is approximately as stiff and substantially stronger, in both flexure and compression but denser. This work contributes to critical knowledge surrounding the microstructure and mechanical properties of bamboo, which are vital to the engineering and design of sustainable SBPs.

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Section: Mechanical Test Resultsmentioning

confidence: 99%

The structure and mechanics of Moso bamboo material

Dixon

Gibson

2014

J. R. Soc. Interface.

281

152

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“…While the reduced moduli are strongly related to the amount and orientation of cellulose, indentation hardness is not directly affected by the MFA (Tze et al 2007) but more closely related to cell wall matrix properties (Gindl et al 2004;Eder et al 2013). Consequently, the variability in hardness across wood species was considerably smaller than the variability in the reduced modulus (Fig.…”

Section: Hardnessmentioning

confidence: 95%

Effect of Water on the Mechanical Properties of Wood Cell Walls – Results of a Nanoindentation Study

Wagner¹,

Bos²,

Bader³

et al. 2015

BioResources

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The paper presents a nanoindentation study on five different wood species in which the elastic and creep properties of the S2 cell wall layer and the middle lamella were determined. Measurements were carried out at relative humidities (RH) ranging from 10 to 80% as well as underwater. Indentation moduli were found to decrease by about a third in the S2 layer and by about half in the middle lamella between RH of 10 and 80%. Hardness dropped by 50 to 60% in this humidity range in both the S2 layer and the middle lamella. Creep parameters were almost constant up to a relative humidity of 40%, but they increased considerably at higher RH. The most pronounced change of reduced moduli and creep properties occurred between 60 and 80% RH, which is consistent with the expected softening of hemicellulose and amorphous parts of cellulose in this humidity region. Immersion into water resulted in a further decrease of the reduced moduli to about 20 to 30% of their values at 10% RH and to only about 10 to 20% for the hardness. This can be explained by additional softening of the less ordered regions of cellulose. Technology, Karlsplatz 13/202, 1040 Vienna, Austria; b: Institute for Applied Materials, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany; c: School of Engineering, University of Glasgow, Glasgow G12 8LT, Scotland, United Kingdom; * Corresponding author: leopold.wagner@tuwien.ac.at Keywords: Nanoindentation; Cell wall; Moisture effects; Creep; Hardwood; Softwood Contact information: a: Institute for Mechanics of Materials and Structures, Vienna University of INTRODUCTIONAdsorbed water significantly reduces the mechanical strength of wood. Individual water molecules are able to diffuse into the wood cell wall ultrastructure and to act as a softening agent. Using nanoindentation, this effect can be studied at the cell wall scale. This eliminates the influences of the cellular structure and the overall mass density of wood, which complicate comparisons between different samples of different wood tissues. Moreover, testing at smaller length scales allows for the probing of different cell wall layers individually. Their different compositions and structures should deliver insight into the effects of water on the material and its mechanical behavior.Nanoindentation was applied to samples of five different wood species, which had undergone extensive microstructural characterization, at four different relative humidities (RH) between 10 and 80% as well as underwater. Both the S2 cell wall layer, which is by far the thickest and stiffest layer, and the middle lamella, which connects neighboring wood cells, were tested. These two layers are crucial for load transfer in wood. The S2 layer withstands axial loads whereas the middle lamella controls the behavior of the wood under shear and in bending. In addition to the reduced modulus, the hardness and creep parameters, in terms of increased deformation under constant loading, were determined. PEER-REVIEWED ARTICLEbi...

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“…It should be noted that since indentation produces a multiaxial stress state beneath the indenter, the reduced modulus is a measurement of a combination of the elastic constants of material. In the case of highly anisotropic materials like wood and bamboo, evaluation of the elastic constants in a particular direction is difficult by indentation (Eder et al, 2013;Gamstedt et al, 2013;Gindl and Schöberl, 2004). Table 2 gives the measured chemical composition of the species.…”

Section: Nanoscale: Nanoindentation Chemical Composition X-ray Scatmentioning

confidence: 99%

Comparison of the structure and flexural properties of Moso, Guadua and Tre Gai bamboo

Dixon

Ahvenainen

Aijazi

et al. 2015

Construction and Building Materials

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Bamboo is an underutilized resource widely available in countries with rapidly developing economies. Structural bamboo products, analogous to wood products, allow flexibility in the shape and dimensions of bamboo structural members. Here, the ultrastructure, microstructure, cell wall properties and flexural properties of three species of bamboo (Moso, Guadua and Tre Gai) are compared. At a given density, the axial modulus of elasticity of Guadua is higher than that of Moso or Tre Gai, which are similar; ultrastructural results suggest that Guadua has a higher solid cell wall stiffness. At a given density, their moduli of rupture are similar.

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Experimental micromechanical characterisation of wood cell walls

Cited by 124 publications

References 90 publications

The structure and mechanics of Moso bamboo material

The structure and mechanics of Moso bamboo material

Effect of Water on the Mechanical Properties of Wood Cell Walls – Results of a Nanoindentation Study

Comparison of the structure and flexural properties of Moso, Guadua and Tre Gai bamboo

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