Relationship among the stiffness, wave propagation speed, density and moisture content of pinus elliottii and bertholletia excelsa wood specimens

Abstract

Wood stiffness is influenced by the moisture content (MC) and density, but little is known about the effect of the wood density on the MC and stiffness relationship. This study evaluated the influence of the moisture content on the dynamic elastic modulus (E) and the wave propagation speed (WPS) of stress waves in wood with low and high basic densities, as well as to verify the effect of the apparent density on the relationship between the stiffness and MC in wood specimens. Pinus elliottii and Bertholletia excelsa trees from experimental plantings were used. Prismatic specimens of wood were used to estimate E and WPS by flexural vibration analyses at equilibrium moisture, after saturation in water and during water desorption until anhydrous conditions. The increase in MC from 12% to 90% caused a reduction of 17% in the wood stiffness and 28% in the WPS, taking into account the samples of the two species. There was no interference of the apparent density of the wood in the MC and stiffness relationship. The elastic moduli showed less variation for the wood species with the highest density. The apparent density does not have a substantial influence on the hygromechanical behavior of wood.