Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
Extractives can affect vibrational properties tanδ (damping coefficient) and E'/ρ (specific Young's modulus) but this is highly dependent on species, compounds, and cellular locations. This paper investigates such effects for African Padauk (Pterocarpus soyauxii Taub.), a tropical hardwood with high extractives content and a preferred material for xylophones. 5 groups of 26 heartwood specimens with large, yet comparable, ranges in vibrational properties were extracted in different solvents. Changes in vibrational properties were set against yields of extracts and evaluation of their cellular location. Methanol (ME) reached most of compounds (13%), located about half in lumen and half in cell-wall. Water solubility was extremely low. tanδ and E'/ρ were very strongly related (R2≥0.93), but native wood had abnormally low values of tanδ, while extraction shifted this relation towards higher tanδ values. ME extracted heartwood became in agreement with the average of many species, and close to sapwood. Extractions increased tanδ as much as 60%, irrespective of minute moisture changes or of initial properties. Apparent E'/ρ was barely changed (+2% to -4%) but, after correcting the mass contribution of extracts, was in fact slightly reduced (down to -10% for high E'/ρ), and increasingly so for specimens with low initial values of E'/ρ.
ISSN: 0043-7719

hal-00804236
https://hal.archives-ouvertes.fr/hal-00804236
https://hal.archives-ouvertes.fr/hal-00804236/document
https://hal.archives-ouvertes.fr/hal-00804236/file/Effect_extractives_vibrational_properties_Bremaud_al.pdf
DOI : 10.1007/s00226-010-0337-3

Éditeur(s) : HAL CCSD Springer Verlag/EDP Sciences
Résumé : International audience
The vibration damping coefficient (tanδ) of wood is an important property for acoustical uses, including musical instruments. Current difficulties in the availability of some of the preferred species call for diversification, but this comes up against the lack of systematic damping coefficient data. * Keeping in mind the possible factors affecting tanδ, could we predict its variations between species, by using indicators that are either easily measured and/or readily available for many species? * Vibrational properties, equilibrium moisture content and colorimetric parameters were assessed on 94 wood types belonging to 76 species. Experimental results were then related to data on chemical contents and physical properties from the CIRAD database. The "standard" relationship between tanδ and specific modulus of elasticity (E'/ρ) explained only half of the variations. Deviations from this trend were correlated to extractives content, yet effects were not directly quantitative. Damping deviations were also correlated to colour and moisture-related properties, especially so with fibre saturation point. * By taking into account a combination of moisture-related properties, colour - or extractives content, and the "standard" relationship between tanδ and E'/ρ, we could propose simple predictive models which explain up to 89% of observed variations in tanδ between 48 species.
ISSN: 1286-4560

hal-00808338
https://hal.archives-ouvertes.fr/hal-00808338
https://hal.archives-ouvertes.fr/hal-00808338/document
https://hal.archives-ouvertes.fr/hal-00808338/file/Physico-chemical_indicators_Bremaud_al.pdf
DOI : 10.1051/forest/2010032