Elastic constants of wood determined by ultrasound using three geometries of specimens

Knowledge of the twelve elastic constants of wood—three moduli of elasticity (E _L, E _R, and E _T), three shear moduli (G _LR, G _LT, and G _RT), and six Poisson’s ratios (μ _LR, μ _RL, μ _RT, μ _TR, μ _LT, and μ _TL)—is essential in some applications, e.g., in simulations or structural calculation software. The methodology for determining these parameters has been developed by different authors, but typically with different samples, which prevents conclusive comparisons. The aim of the present study was to assess both the methods and associated results of using ultrasound technology on three geometric specimens—multifaceted discs, polyhedrons, and prisms—to characterize samples from three wood species: Eucalyptus saligna, Apuleia leiocarpa, and Goupia glabra. The results from the ultrasound and static compression tests on the prism were obtained from another study by the authors’ group and used for a comparative analysis because the species belonged to the identical sample. In general, the moduli of elasticity and shear moduli were statistically equivalent to those obtained by the static test for the three geometries of the specimens. The results of the Poisson’s ratios depended on the type and geometry of the specimens. The polyhedral geometry showed the best results, whereas the prismatic results were the least suitable. From a methodological perspective, the polyhedron was easier to apply.