Variations in orthotropic elastic constants of green Chinese larch from pith to sapwood

Abstract

Full sets of elastic constants of green Chinese larch (Larix principis-rupprechtii Mayr) with 95% moisture content at four different cross-section sampling positions (from pith to sapwood) were determined in this work using three-point bending and compression tests. Variations in the material constants of green Chinese larch from pith to sapwood were investigated and analyzed. The results showed that the sensitivity of each elastic constant to the sampling position was different, and the coefficient of variation ranged from 4.3% to 48.7%. The Poisson's ratios vRT measured at four different sampling positions were similar and the differences between them were not significant. The coefficient of variation for Poisson's ratio vRT was only 4.3%. The four sampling positions had similar Poisson's ratios vTL, though the coefficient of variation was 11.7%. The Poisson's ratio vLT had the greatest variation in all elastic constants with a 48.7% coefficient of variation. A good linear relationship was observed between the longitudinal modulus of elastic EL, shear modulus of elasticity GRT, Poisson's ratio vRT, and sampling distance. EL, GRT, and vRT all increased with sampling distance R. However, a quadratic relationship existed with the tangential modulus of elasticity ET, radial modulus of elasticity ER, shear modulus of elasticity GLT, and shear modulus of elasticity GLR. A discrete relationship was found in the other five Poisson's ratios. The results of this study provide the factual changes in the elastic constants of green wood from pith to sapwood for numerical modelling of stress wave propagation in trees or logs.