Wood material - Structure and features

Wood is a rigid plant tissue, composed of cells with lignocellulose walls that are particularly efficient from a mechanical point of view. This is what has enabled trees to set records for size and longevity in the living world.

The anatomy of wood is complex and presents a wide variety of "woody plans", as it has been the subject of numerous adaptive innovations selected over the course of evolution. Indeed, certain anatomical features enable plants to better resist environmental constraints, such as the risk of drought or frost. Anatomy reflects a strategy or compromise that enables the tree to perform the various biological functions of wood safely and efficiently.

Knowledge of anatomy enables us not only to identify woody species, but also to understand their physical and mechanical properties.

The wide variety of woods offers a wide range of choices, with each wood presenting certain technological aptitudes that make it more or less suitable for different uses.

Knowledge of wood "species" is essential to optimize this choice. Since wood is the product of living organisms, there is a great deal of variability within the same species, both genetically and in terms of growth conditions.

Wood intended for industry is therefore graded, i.e. divided into commercial categories according to quality criteria specific to each species.

Wood was one of the first materials used by man. Over the centuries, and through a multitude of experiments, human beings the world over have been able to associate the most suitable wood with a given manufacture.

Here are a few examples from Europe:

• yew arches ;

• oak barrels ;

• Ash tool handles;

• butcher's blocks in charm ;

• elm wheel hubs ;

• walnut rifle stocks ;

• sculptures in lime ;

• corm gear teeth...

This invaluable empirical knowledge has now been verified and supplemented by scientific characterization tools for today's uses of wood.

Materials science does not work along a single axis (e.g. the search for a high mechanical property); on the contrary, it constantly seeks an optimum compromise between several, often contradictory, properties:

• a material with high hardness and non-brittle behavior;

• an artificial composite with a very high modulus of elasticity and low cost, etc.

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