Laboratory of Forest Resource Circulating Circles, Graduate School of Life and Environment Science, Kyoto Prefectural University, Japan.
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Laboratoire de M'ecanique et G'enie Civil, Universit'e Montpellier 2, CNRS, Montpellier, France.

Mechanical damping of wood in given conditions of time-frequencies, temperature and moisture content is related to superimposed effects of the orientation of wood elements (cells and microfibrils) and of characteristics of chemical composition. Such affecting factors may in turn be markers of the botanical classification or phylogeny of woody species. Especially, secondary metabolites are extremely diverse and their nature depends on families, genus or species. They are also expected to play a significant, and probably compound-dependant, role in modulating mechanical damping. Though, considering actual biodiversity, little information is currently available about inter-specific variability of mechanical damping.
This work is a first insight into the potential categorization of taxon depending on their mechanical damping. It relies on the gathering of a large collection of information on the viscoelastic (i.e. including damping) vibrational properties of 450 woody species. Data come from our experimental campaigns of characterization and from an exhaustive review of existing literature. In the scope of comparing damping characteristics, data are "normalized" using two indicators that are more or less de-correlated from the strong relationship to specific elastic (= storage) modulus. These indicators - specific loss modulus and "normalized damping" - are compared between 25 families of gymnosperms and angiosperms, represented by at least 5 species each. First results indicate that some families appear to have nearly systematically lower (Leg.-Papilionaceae, Moraceae, Cupressaceae) or higher (Fagaceae, Betulaceae, Sapindaceae) damping than average. While for some other families no clear characteristics can be observed - at least with the present number of represented species. Further analysis shall concern the genus and species level, where enough information is available. It is hoped to increase the amount of information in order to get a broader view of the topic: more numerous species, links between mechanical data and specific affecting factors.