La chimie du bois a-t-elle un impact sur son comportement mécanique ?

Wood is a major class of structural materials, renowned for its highly variable mechanical properties. Chemistry provides a good definition of the fundamental unity of wood: polymers rich in carbon, oxygen and hydrogen, impregnated with numerous bioactive organic molecules known as extractives. But it does little to explain the variations in rigidity or strength of the wood used. It is the physical structure on two scales: a honeycomb-type cellular material on a micrometric scale and an oriented-fibre composite on a nanometric scale, which explains almost all these variations. Nevertheless, the “viscous” component of the viscoelastic behaviour of wood, which indicates the acoustic damping of wood, is closely linked either to the proportions of monomers in the wood polymers, or to particular molecules in the cocktail of extractives. Finally, the formation of a tree’s skeleton, like 3D printing, is the result of the growth of the living tissue that is the wood itself, in a thin peripheral sleeve beneath the bark. Peripheral forces, essential for controlling the tree’s posture, are generated during lignification associated with the programmed death of the wood fibres. Once again, these forces are regulated by controlling the proportions of monomers.