14. Development and experimental verification of a continuum micromechanics model for the elasticity of wood
A multistep homogenization scheme is found to adequately represent the intrinsic structural hierarchy of wood across all different tree species. The nanoscaled components of the wood cell wall, namely crystalline cellulose, amorphous cellulose, hemicellulose, lignin, and water, exhibit universal elastic properties inherent to all wood species. They allow for prediction of wood tissue-specific macroscopic elastic properties from tissue-specific chemical composition and microporosity by means of a four-step homogenization scheme.
Validation of the presented continuum micromechanics model rests on statistically and physically independent experiments: The macroscopic material stiffness predicted by the micromechanical model on the basis of tissue-independent ('universal') phase stiffness properties of hemicellulose, amorphous cellulose, crystalline cellulose, lignin, and water for tissue-specific composition data are compared to corresponding experimentally determined tissue-specific stiffness values. For the elastic moduli in the longitudinal direction (aligned with the stem axis), EL, and in the transverse direction (in the cross-sectional plane of the stem), ETrans, as well as for the longitudinal shear modulus, GLTrans, model estimates and experimental results show good agreement over a large variety of softwood and hardwood species.