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Etude des propriétés mécaniques et du retrait au séchage du bois à l'échelle de la paroi cellulaire : essai de compréhension du comportement macroscopique paradoxal du bois de tension à couche gélatineuse

Abstract : Growth stresses, longitudinal MOE in green and air-dry conditions and shrinkage in longitudinal and tangential directions were measured on 96 chestnut small samples characterised on the standing tree by a prestress ranging from a slight compression to a strong tension. On these samples, anatomical observations allowed to determine the content in fibres with a gelatinous layer (G layer). The influence of these atypical fibres on macroscopic wood properties is examined and discussed and their properties in theoretically isolated conditions are determined using a basic model.
Fibres with G layer seeming to be the driving force of the strong axial shrinkage of tension wood, an observation of the drying behaviour on the cell wall scale is finalised. Observations with scanning electron microscopy and atomic force microscopy show that, besides its strong transverse shrinkage, the G layer exhibits also a very strong longitudinal shrinkage. A simple modelling approach of with finite elements is proposed to account for the observed phenomena.
To obtain the data required for the modelling, two tools are finalised for an estimation of elastic and viscoelastic properties of the cell wall layers. The development of a transmission acoustic microscope and the use of the atomic microscopy in vibrating contact mode allow to envisage the quantitative characterisation of mechanical properties at the cell wall scale in various humidity conditions.
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Contributor : Bruno Clair <>
Submitted on : Wednesday, March 23, 2005 - 5:55:19 PM
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Bruno Clair. Etude des propriétés mécaniques et du retrait au séchage du bois à l'échelle de la paroi cellulaire : essai de compréhension du comportement macroscopique paradoxal du bois de tension à couche gélatineuse. Sciences du Vivant [q-bio]. ENGREF (AgroParisTech), 2001. Français. ⟨tel-00008857⟩

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