Mechanics of wood and trees: some new highlights for an old story

The main aspects of wood mechanics are approached through the role played b y wood as the building material of the tree. The main concepts used by natu re: progressive setting up of tree weight and architecture, multifunctional role of wood and adaptability to hazard and long-term evolution, are clari fied together with their consequence on the multilayered, anisotropic natur e of wood. The technological choices of the plant world as the, cellular st ructure, the use of composite with oriented fibres and hydro-carbonated pol ymers, as well as the systematic prestressing of every new layer, bear obvi ous consequences on the type of mechanical behaviour of wood. The local con trol of the level of prestressing through minor modifications of the cell-w all biosynthesis allows the tree to adapt to conditions of light exploratio n that will evolve according to time and risk occurrence. This analysis of wood genesis process permits in return to improve our understanding of the mechanical behaviour of the material in relation with the parameters of the microstructure. (C) 2001 Academie des sciences/Editions scientifiques et m edicales Elsevier SAS.