Mechanical Properties of Black Locust (Robinia pseudoacacia) Wood: Correlations among Elastic and Rupture Moduli, Proportional Limit, and Tissue Density and Specific Gravity

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Abstract
The purpose of this paper is to determine the extent to which the physical and mechanical properties of dry and green wood samples are correlated. Samples of green (fresh) sap- and heartwood differing in density (rho) were removed from the trunk of a black locust (Robinia pseudoacacia L.) tree 30 years old and measuring 15 m in height. These samples were mechanically tested to determine their Young's elastic modulus (E), proportional (elastic) limit (sigma(p)), and modulus of rupture (sigma(R)). The Young's elastic modulus of green wood samples increased in magnitude to a limit with increasing cross-sectional area of the sample tested. The values of all three mechanical parameters measured for sapwood samples were consistently lower than those measured for heartwood samples with equivalent cross-sectional areas. E was linearly and positively correlated with the sigma(p) and sigma(R) of heartwood tissue samples. All mechanical p properties were highly correlated with the density of green heartwood. Likewise, these properties were highly correlated with the specific gravity of wood samples. Based on these results, it is concluded that either the density of fresh wood or the specific gravity of air-dried wood can be used to estimate :he mechanical properties of black locust wood based on simple regression curves in the absence of extensive mechanical tests. (C) 1997 Annals of Botany Company.

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