Nanoindentation of wood cell walls: Continuous stiffness and hardness measurements

W. T.Y. Tze; S. Wang; T. G. Rials; G. M. Pharr; S. S. Kelley

doi:10.1016/j.compositesa.2006.06.018

Nanoindentation of wood cell walls: Continuous stiffness and hardness measurements

W. T.Y. Tze, S. Wang, T. G. Rials, G. M. Pharr, S. S. Kelley

Bioproducts and Biosystems Engineering

Research output: Contribution to journal › Article › peer-review

164 Scopus citations

Abstract

The objective of this study was to measure the mechanical properties of individual, native wood fibers using the continuous nanoindentation measurement technique. The indentation depth profile exhibited a small length-scale effect, which was confirmed using the size-effect index derived from the indentation loading curve. The hardness (H_u) or stiffness (E_u) values determined from indentation unloading were also examined for 10 different annual rings of a loblolly pine, with microfibril angles (MFA) between 14° and 36°. A predictable pattern of E_u values was found as a function of MFA, and hence E_u can at least be considered a relative measure of the longitudinal stiffness properties of wood cell walls. For H_u values, a dependence on orientation was observed, and there is a preliminary indication that the dependence could be affected by cell-wall extractives. It is thus desirable, for cell-wall modification studies, to minimize any unintended variations by using samples that are from the same growth ring, so that any treatment-induced changes in the cell-wall hardness can be identified.

Original language	English (US)
Pages (from-to)	945-953
Number of pages	9
Journal	Composites Part A: Applied Science and Manufacturing
Volume	38
Issue number	3
DOIs	https://doi.org/10.1016/j.compositesa.2006.06.018
State	Published - Mar 2007

Bibliographical note

Funding Information:
The authors would like to acknowledge financial supports from the USDA Wood Utilization Research Program, the National Research Initiative (grant number 2003-35103-13638) of the USDA Cooperative State Research, Education and Extension Service and the Tennessee Agricultural Experiment Station (Project MS #83). Instrumentation for the nanoindentation work was provided through the SHaRE Program at the Oak Ridge National Laboratory, which was sponsored by the Division of Materials Science and Engineering, US Department of Energy, under contract DE-AC05-000R22725 with UT-Battelle, LLC. The authors also thank Dr. John Dunlap of the University of Tennessee Electron Microscopy Laboratory for assisting in the microtome sectioning of the samples, and Dr. Andrei Rar of the Oak Ridge National Laboratory for technical supports in nanoindentation tests.

Keywords

A. Wood
B. Mechanical properties
Nanoindentation

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title = "Nanoindentation of wood cell walls: Continuous stiffness and hardness measurements",

abstract = "The objective of this study was to measure the mechanical properties of individual, native wood fibers using the continuous nanoindentation measurement technique. The indentation depth profile exhibited a small length-scale effect, which was confirmed using the size-effect index derived from the indentation loading curve. The hardness (Hu) or stiffness (Eu) values determined from indentation unloading were also examined for 10 different annual rings of a loblolly pine, with microfibril angles (MFA) between 14° and 36°. A predictable pattern of Eu values was found as a function of MFA, and hence Eu can at least be considered a relative measure of the longitudinal stiffness properties of wood cell walls. For Hu values, a dependence on orientation was observed, and there is a preliminary indication that the dependence could be affected by cell-wall extractives. It is thus desirable, for cell-wall modification studies, to minimize any unintended variations by using samples that are from the same growth ring, so that any treatment-induced changes in the cell-wall hardness can be identified.",

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author = "Tze, {W. T.Y.} and S. Wang and Rials, {T. G.} and Pharr, {G. M.} and Kelley, {S. S.}",

note = "Funding Information: The authors would like to acknowledge financial supports from the USDA Wood Utilization Research Program, the National Research Initiative (grant number 2003-35103-13638) of the USDA Cooperative State Research, Education and Extension Service and the Tennessee Agricultural Experiment Station (Project MS #83). Instrumentation for the nanoindentation work was provided through the SHaRE Program at the Oak Ridge National Laboratory, which was sponsored by the Division of Materials Science and Engineering, US Department of Energy, under contract DE-AC05-000R22725 with UT-Battelle, LLC. The authors also thank Dr. John Dunlap of the University of Tennessee Electron Microscopy Laboratory for assisting in the microtome sectioning of the samples, and Dr. Andrei Rar of the Oak Ridge National Laboratory for technical supports in nanoindentation tests.",

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N2 - The objective of this study was to measure the mechanical properties of individual, native wood fibers using the continuous nanoindentation measurement technique. The indentation depth profile exhibited a small length-scale effect, which was confirmed using the size-effect index derived from the indentation loading curve. The hardness (Hu) or stiffness (Eu) values determined from indentation unloading were also examined for 10 different annual rings of a loblolly pine, with microfibril angles (MFA) between 14° and 36°. A predictable pattern of Eu values was found as a function of MFA, and hence Eu can at least be considered a relative measure of the longitudinal stiffness properties of wood cell walls. For Hu values, a dependence on orientation was observed, and there is a preliminary indication that the dependence could be affected by cell-wall extractives. It is thus desirable, for cell-wall modification studies, to minimize any unintended variations by using samples that are from the same growth ring, so that any treatment-induced changes in the cell-wall hardness can be identified.

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Nanoindentation of wood cell walls: Continuous stiffness and hardness measurements

Abstract

Bibliographical note

Keywords

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