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Accessible Unlicensed Requires Authentication Published by De Gruyter June 1, 2005

Influence of grain direction in vibrational wood welding

Milena Properzi, Jean-Michel Leban, Antonio Pizzi, Stephanie Wieland, Frederic Pichelin and Mario Lehmann
From the journal

Abstract

Wood grain orientation differences in the two surfaces to be bonded yield bondlines of different strength in no-adhesives wood welding. Longitudinal wood grain bonding of tangential and radial wood sections yields an approximately 10% difference in strength results of the joint. Cross-grain (±90°) bonding yields instead a much lower strength result, roughly half that observed for pieces bonded with the grain parallel to each other. These differences can be explained by the very marked effect that homogeneity of fibre orientation is known to have on fibre–matrix composites. Oak yields lower results than beech and maple and is more sensitive to welding conditions. Differences in both anatomical and wood constituent composition can account for this difference in performance. Contrary to the other wood species, oak always presents joint bondlines where little or no increase in density at the interface is noticed. This explains its somewhat lower strength results. This is based on the different mode of bonding predominant in this species, while the other species present two different modes of bonding. Thus, two types of bondlines are observed by scanning electron microscopy (SEM): (i) bondlines where entangled fibre–matrix composites are formed at the interface and (ii) bondlines in which direct welding of the cell walls occurs, just by fused intercellular material or cell surface material. In this latter case the cells remain flat, without an entangled fibre–matrix composite being formed. This is the almost exclusively predominant case for oak. Both cases and even hybrid cases between the two have also been observed in beech.

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Corresponding author. ENSTIB-LERMAB, University of Nancy 1, BP 1041, 88051-Epinal Cedex 9, France

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Published Online: 2005-06-01
Published in Print: 2005-01-01

©2004 by Walter de Gruyter Berlin New York