Paramètres structuraux et/ou ultrastructuraux facteurs de la variabilité intra-arbre de l'anisotropie élastique du bois

Abstract

Three levels of modelling are introduced to simulate the elastic anisotropy of solid clear softwood, from the cell wall level, via wooden tissues, to the annual ring level. The micro-mechanical models used, at each step, are based on the homogeneous elastic equivalent solid method. Quite simple mixture laws are used for series or parallels assembling of two assumed homogeneous media. 17 realistic parameters are identified by optimisation on the base of given orthotropic elastic properties of the "standard softwood". The modelling tool allows analysing the sensibility of elastic parameters to the variability of internal structural parameters even if it doesn't express quite the ultrastructural reality. One of the originalities is include in cellular wall schematization by a unique layer, reinforcing by a microfibrille skeleton, in which the microfibrillar orientation belongs to S2 layer. The stiffening of this skeleton, in front of a structure with parallels fibers, represents the cell walls tranverses reinforcements generally assigned to S 2 and S3 layers.