Summary A range of mechanical and physical properties were determined for 96 specimens of chestnut wood and for wood types ranging from compression to tension wood; tests included (1) growth stress, (2) longitudinal Young's modulus in green and air-dried states (3) shrinkage in longitudinal and tangential directions. Anatomical observations permitted determination of the proportion of fibres with a gelatinous layer. The influence of these atypical fibres on macroscopic wood properties is examined and discussed. A basic model is proposed to determine their properties in theoretically isolated conditions.

Generally speaking, charcoal analysis is based on identifying and counting charcoal fragments in order to calculate the relative variations in taxa frequency. All post-depositional processes are likely to induce fragmentation of the anthracological material, raising the question of the representativeness of taxa. Based on an innovative experimental approach combining both charcoal analysis and biomechanics, this paper explores how the mechanical properties of charcoal can influence the fragmentation and the quantification of species in anthracological assemblages. We carried out standardized laboratory compression tests on 302 samples issued from 10 taxa, charred at three different temperatures, in order to characterize the mechanical properties of common species in temperate and Mediterranean Europe. Our results highlight the differential responses of the tested species in terms of resistance to compression and fragmentation, two processes which do not appear to be correlated. Charcoal is very resistant to pressure (up to 22.5 MPa). Our results show that significant fragmentation differences exist between taxa. The total number of fragments after compression is largely dependent on the species, regardless of the charring temperature. However, this interspecific variability is more significant for small fragments [1e2 mm], than for larger fragments [2e4 mm] and >4 mm, with the exception of Quercus, which displays differential reactions to compression. Finally, a multifactorial analysis brings to light the impact of the physical and anatomical characteristics of the different species on charcoal fragmentation.

The anisotropy of vibrational properties influences the acoustic behaviour of wooden pieces and their dependence on grain angle (GA). As most pieces of wood include some GA, either for technological reasons or due to grain deviations inside trunks, predicting its repercussions would be useful. This paper aims at evaluating the variability in the anisotropy of wood vibrational properties and analysing resulting trends as a function of orientation. GA dependence is described by a model based on transformation formulas applied to complex compliances, and literature data on anisotropic vibrational properties are reviewed. Ranges of variability, as well as representative sets of viscoelastic anisotropic parameters, are defined for mean hardwoods and softwoods and for contrasted wood types. GAdependence calculations are in close agreement with published experimental results and allow comparing the sensitivity of different woods to GA. Calculated trends in damping coefficient (tand) and in specific modulus of elasticity (E 0 /q) allow reconstructing the general tand-E 0 /q statistical relationships previously reported. Trends for woods with different mechanical parameters merge into a single curve if anisotropic ratios (both elastic and of damping) are correlated between them, and with axial properties, as is indicated by the collected data. On the other hand, varying damping coefficient independently results in parallel curves, which coincide

International audienceContext Increased knowledge on diversity in wood properties would have implications both for fundamental research and for promoting a diversification of uses as material. *Aims The objective is to contribute to overcoming the critical lack of data on the diversity of wood dynamic mechanical/viscoelastic vibrational properties, by testing lesser-known species and categorizing sources of variability. *Methods Air-dry axial specific dynamic modulus of elasticity (E'/γ) and damping coefficient (tanδ) were measured on a wide sampling (1792 specimens) of 98 wood types from 79 species. An experimental device and protocol was designed for conducting systematic (i.e. rapid and reproducible) characterizations. *Results Diversity at the specimens' level corroborates the "standard" relationship between tanδ and E'/γ, which is discussed in terms of orientation of wood elements and of chemical composition. Diversity at the species level is expressed on the basis of results for normal heartwood, with specific gravity (γ) ranging from 0.2 to 1.3. Axial E'/γ ranges from 9 to 32 GPa and tanδ from 4×10-3 to 19×10-3. Properties distribution follows a continuum, but with group characteristics. The lowest values of tanδ are only found in certain tropical hardwoods. Results can also suggest alternative species for musical instruments making