Influence of Growth Ring Number and Width on Elastic Constants of Poplar

The objective of this work was to evaluate the effect of growth ring number (specimens including 2, 4, and 6 rings from the bark) and growth ring width on elastic constants in the radial direction of Populus x canadensis, which has not been revealed before. The longitudinal (2.25 MHz) and transverse (1 MHz) ultrasonic waves were propagated to calculate the longitudinal (V-RR) and shear (V-RL, V-LR, V-TR, and V-RT) wave velocities and used to determine the elasticity modulus (E-R), and shear moduli (G(RL) and G(RT)). The average growth ring widths of specimens including 2, 4, and 6 rings were 17.0 mm, 17.8 mm, and 18.2 mm, respectively. According to the results, only V-RL steadily increased with increased ring number, while other velocities fluctuated. The same fluctuations were observed for moduli except for G(LR), which constantly increased with ring number. The influence of ring number on velocity was statistically significant only for V-RL and V-RT. However, all moduli were significantly affected by ring number. Linear regression statistics revealed that there were significant relations between the ring width and density, V-RL, V-LR, V-RT, G(RL), and G(RT).