Hygromechanical properties of grenadilla wood ( Dalbergia melanoxylon )
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Hygromechanical properties of grenadilla wood (Dalbergia melanoxylon) Ahmad Alkadri1,2 · Delphine Jullien2 · Olivier Arnould2 · Eric Rosenkrantz3 · Patrick Langbour4 · Louise Hovasse1 · Joseph Gril5 Received: 3 December 2019 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Grenadilla wood (Dalbergia melanoxylon Guill. & Perr.) is a hardwood species found in Tanzania, Mozambique, and other countries in the tropical part of Africa, especially in the Eastern-Central region. Thanks to its high density and good hygroscopic stability, it is used in the making of various musical instruments and fine furniture. Due to the scarcity of published data on this wood species, more studies on its properties are needed to improve its processing and use, and even to search for sustainable alternative materials as its trade is increasingly limited by new regulations. This work is focused on the hygromechanical properties, which hold an important role in the applications of this wood: diffusion coefficients and adsorption–desorption curve (both measured at T = 20 ◦ C ), swelling–shrinkage coefficients and full orthotropic elastic constants using an ultrasonic method. Results show that grenadilla wood possesses small water diffusion coefficients (from 1.54 ± 0.49 × 10−7 cm2 ∕s in T direction to 4.58 ± 0.84 × 10−7 cm2 ∕s in L direction), which is probably related to its high density ( 1250.0 ± 26.2 kg∕m2 ); unique equilibrium moisture content (sorption) curve with a lower fiber saturation point ( 0.173 ± 0.003 ); smaller swelling– shrinkage coefficients ( 0.20 ± 0.03 and 0.32 ± 0.05 in T and R directions, respectively); and elastic constants lower in the longitudinal direction ( 15.56 ± 1.79 GPa) and higher in the transverse ones ( 5.10 ± 0.46 GPa and 4.05 ± 0.35 GPa in R and T directions, respectively) than what could be expected with a standard model based on the density only. Several explanations were described here, from the effects of a high extractive content to the possibility of a high microfibril and/or fiber angle. List of symbols L Longitudinal direction R Radial direction T Tangential direction c Diffusing concentration * Ahmad Alkadri [email protected] Extended author information available on the last page of the article
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Wood Science and Technology
ci Initial diffusing concentration cf Final diffusing concentration Mt Total change of moisture content at a given time t Mf Total final change of moisture content [C] Stiffness matrix Cij Component of stiffness matrix [S] Compliance matrix, where [C] = [S]−1 DL A code designating a diffusion sample for L direction DR A code designating a diffusion sample for R direction DT A code designating a diffusion sample for T direction D Coefficient of diffusion, written here as cm2 ∕s [D] Matrix of diffusion coefficients, which consists of D for diffusion in L, R and T D0 Constant diffusion coefficient D Dlin Coefficient of diffusion whose values vary linearly with W De Coefficient of diffusion whose values v
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