Nanoindentation of wood cell walls: effects of sample preparation and indentation protocol
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Nanoindentation has become a valuable tool in wood science. It enables to examine the mechanical properties of the wood cell walls, which are polymeric, multi-layered structures with typical thicknesses of a few micrometers. Despite the intensive use of the method for the characterization of wood cell walls, it is not entirely clear yet how the measurement results may be affected by the way the sample is prepared and the indentation is carried out. This manuscript contributes to clarify these issues, by presenting indentation data for a variety of sample preparation techniques and indentation protocols, and by critically evaluating the observed differences of the obtained indentation moduli and hardnesses. Investigations covered the effect of different embedding materials, including testing of non-embedded cell walls, and of repeated exposure to high temperatures during harsh drying before the indentation test. Moreover, potential edge effects were studied when the indentation size approaches the width of the individual cell wall layers. Using different embedding materials as well as testing non-embedded cell walls did not lead to significant changes in the measured properties. Due to damage during the sample preparation, non-embedded cell walls tend to show substantially higher experimental scatter. Repeated drying prior to embedding had no significant effect on the resulting moduli and hardnesses. Finally, it was found that reasonable mechanical properties can be extracted from the cell corner middle lamella (CCML), even when the size of the indent approaches the diameter of the CCML.
KeywordsIndentation Depth Wood Cell Wall Nanoindentation Test Indentation Modulus Resin Penetration
The authors would like to acknowledge the financial support from the Vienna University of Technology via the Innovative Project: “Microstructural and chemical characterization of softwood degradation by basidiomycetes and its effects on the mechanical behavior”.
- 1.Back E, Salmén L (1982) Tappi J 65(7):107Google Scholar
- 4.EN 13183-1–2002 Moisture content of a piece of sawn timber – Part 1: Determination by oven dry method. Brussels, Belgium, European Committee for Standardization (CEN) 2002Google Scholar
- 8.Irvine GM (1984) Tappi J 67(5):118Google Scholar
- 12.Kamke FA, Lee JN (2007) Wood Fiber Sci 39(2):205Google Scholar
- 13.Kim J-W, Harper DP, Taylor AM (2012) Wood Fiber Sci 44(1):103Google Scholar
- 16.Konnerth J, Harper D, Lee SH, Rials TG, Gindl W (2008) Holzforschung 62:91Google Scholar
- 22.Olsson A-M, Salmen L. (1997) Humidity and temperature affecting hemicellulose softening in wood. In: Proceedings of International Conference of COST Action E8, Copenhagen, Denmark, June 16–17, 1997. p 269Google Scholar
- 24.Sedighi-Gilani M, Sunderland H, Navi P (2006) Wood Fiber Sci 38(1):132Google Scholar
- 25.Senft JF, Bendtsen BA (1985) Wood Fiber Sci 17:564Google Scholar
- 29.Wimmer R, Lucas BN (1997) IAWA J 18(1):77Google Scholar
- 30.Wimmer R, Lucas BN, Tsui TY, Oliver WC (1997) Wood Sci Technol 31(2):131Google Scholar