The effects of tree age, thickness, and depth of timber on density and mechanical properties of heat-treated black poplar wood (Populus nigra)

Abstract

ThermoWood is a wood modification method that is used to improve the wood application and dimensional stability of wood. In this study, poplar wood (Populus nigra) was used in two age groups of 18- and 38-year-old trees to investigate the effect of tree age, thickness, and depth of heat-treated timbers on mechanical properties and density. In each age group, the timbers were prepared according to thickness of 40, 50, and 60 mm. The experimental samples were prepared from the surface (S) and middle (M) depth of heat-treated timbers based on age and thickness. Some properties of heat-treated and control wood such as density (oven-dry density, air-dry density, and basic density) and mechanical properties (modulus of rupture (MOR), modulus of elasticity (MOE), and impact strength) were measured. In general, density and mechanical properties of heat-treated wood were decreased compared with the control samples. Density and mechanical properties of heat-treated and control wood samples were increased from 18- to 38-year-old trees. There were no differences in density and mechanical properties after changing thickness. Surface and middle depth specimens of heat-treated timbers showed a positive effect on the impact strength but had no considerable effect on densities and other strengths of heat-treated wood timbers.

Effect of tree age on the properties of Himalayan birch (Betula alnoides Buch.-H.ex D.Don) wood

“…This difference is caused by the increased density of older trees (Bijak and Lachowicz 2021). Hassani et al (2022) found that the mechanical properties of Populus nigra increased when the age of tree increased. They related it with the fiber length and cell wall thickness, which affect the increasing of density of the wood.…”