Conception et exploitation d'un dispositif expérimental innovant pour la caractérisation du comportement viscoélastique et de la dégradation thermique du bois dans des conditions sévères

Abstract : Because of its biological origin, the wood properties are highly variable and therefore its characterisation is sometimes complex. An improved knowledge of the rheological properties and more particularly of the viscoelastic properties is needed for the development and the optimisation of wood processing and manufacturing based on wooden materials. The main purpose of this work is to characterise the time-dependent behaviour of green wood in water content and temperature-controlled conditions. An experimental device, perfectly adapted to the wood specificity and particularly to its anisotropy and hygroscopicity, was developed. This apparatus, the WAVET (Environmental Vibration Analyser for Wood), permits the determination of the viscoelastic properties of wood using harmonic tests in single cantilever bending for frequencies varying between 5.10-3 Hz and 10 Hz. Conceived to work up to about 5 bars, it allows tests in dry or water-saturated conditions to be performed over a temperature range from 0ÊC to 140ÊC. The results collected for several temperate species using the WAVET emphasise the influence of numerous parameters on the rheological properties and notably on the softening temperature, namely specie, material direction, wood type (normal/reaction) and anatomical and macromolecular structure. The study of the thermal degradation of green wood reveals noticeable modifications in the biochemical composition of this biopolymer. The elastic and damping properties of thermally-treated wood in water-saturated conditions change a lot according to the severity of the treatment and the native structure of the constitutive macromolecules.
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Vincent Placet. Conception et exploitation d'un dispositif expérimental innovant pour la caractérisation du comportement viscoélastique et de la dégradation thermique du bois dans des conditions sévères. Autre. Université Henri Poincaré - Nancy 1, 2006. Français. ⟨NNT : 2006NAN10102⟩. ⟨tel-01748158⟩

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