Abstract

Recent developments in the fields of physics, chemistry, and materials science allow for studying wood at increasingly smaller length scales, and have given a much deeper understanding of its structure at the nanoscale and of the molecular interactions upon mechanical loading or changes of environmental conditions. Combining multiscale modeling with computational simulations makes this knowledge useful for timber engineering purposes. For instance, it enables to quantitatively assess the variability of the macroscopic material properties of wood as typically observed for tests at the centimeter scale and to resolve the (thermo-hygro-mechanical) couplings at this scale.

The multiscale approach starts at the length scale of nanometers, where universal constituents with sample-independent properties, namely hemicelluloses, lignin, and cellulose, are encountered. Their arrangement in terms of a fiber-reinforced composite in the wood cell wall and the honeycomb pattern of the wood cells is accomplished via a multistep homogenization scheme. It is shown how this methodology can be applied to investigate structure-property relations for hardwood in terms of its stiffness, and how to translate failure and creep mechanisms observed at the microscale to corresponding macroscopic properties of clear wood. Subsequently, constitutive equations suitable for structural simulations can be derived.