Identification of anisotropic vibrational properties of Padauk wood with interlocked grain

Iris Brémaud (1) , Pierre Cabrolier (2) , Joseph Gril (1) , Bruno Clair (1) , Jean Gérard (3) , Kazuya Minato (4) , Bernard Thibaut (5)

1 MAB - Mécanique de l'Arbre et du Bois
2 LMGC - Laboratoire de Mécanique et Génie Civil
3 UPR Bois tropicaux - Production et valorisation des bois tropicaux
4 Laboratory of Forest Resources Circulatory System
5 ECOFOG - Ecologie des forêts de Guyane

Grain deviations and high extractives content are common features of many tropical woods. We aimed at clarifying their respective impact on vibrational properties, referring to African Padauk (Pterocarpus soyauxii Taub.), a species selected for its interlocked grain, high extractives content, and uses in xylophones. Specimens were cut parallel to the trunk axis (L), and local variations in grain angle (GA), microfibril angle (MFA), specific Young's modulus (E'L/ρ, where r stands for specific gravity) and damping coefficient (tanδL), were measured. GA dependence was analyzed by a mechanical model which allowed to identify the specific Young's modulus (E'3/ρ) and shear modulus (G'/ρ) along the grain (3), as well as their corresponding damping coefficients (tanδ3, tanδG). This analysis was done for native and then for extracted wood. Interlocked grain resulted in 0-25° GA and in variations of a factor 2 in E'L/ρ and tanδL. Along the grain, Padauk wood was characterized, as compared to typical hardwoods, by a somewhat lower E'3/ρ and elastic anisotropy (E'/G'), due to a wide microfibril angle plus a small weight effect of extracts; and a very low tanδ3 and moderate damping anisotropy (tanδG/tanδ3). Extraction affected mechanical parameters in the order: tanδ3 ≈ tanδG > G'/ρ >> E'3/ρ. That is, extractives' effects were nearly isotropic on damping but clearly anisotropic on storage moduli.

Mots clés: Anisotropy; Damping coefficient; Extractives; Grain angle; Interlocked grain; Microfibril angle; Vibrational properties; Young's modulus

Domaines: Autre

Iris Brémaud, Pierre Cabrolier, Joseph Gril, Bruno Clair, Jean Gérard, et al.. Identification of anisotropic vibrational properties of Padauk wood with interlocked grain. Wood Science and Technology, 2010, 44 (3), pp.355-367. ⟨10.1007/s00226-010-0348-0⟩. ⟨hal-00544382⟩