Comparative Experimental Investigation of Two Different Levels of Heat-Treated Wood Properties

This study examines the effects of heat treatment on the mechanical properties of four wood species: oak (Quercus petraea L), Scotch pine (Pinus sylvestris), chestnut (Castanea sativa) and cedar (Cedrus libani). Samples were subjected to heat treatment at 175 °C and 205 °C, and their bending strength, modulus of elasticity, compression strength, dynamic bending (shock) strength, column strength, and hardness were compared with untreated controls. Results revealed that wood species, treatment temperature and their interaction significantly influenced all mechanical properties. Oak consistently showed the highest performance, while cedar exhibited the lowest values. Heat treatment caused notable reductions in mechanical properties, with losses ranging from 0.2 % to 52.2 % at 175 °C and increasing further at 205 °C. The reduction is attributed to the thermal degradation of wood components such as cellulose, hemicellulose and lignin, leading to weakened cell walls and increased brittleness. Lower temperatures primarily produced a pre-treatment and drying effect, while higher temperatures intensified chemical degradation. Among the properties tested, bending strength, modulus of elasticity and hardness were most affected. The findings demonstrate that heat treatment significantly alters the mechanical performance of wood, and these changes must be considered in structural and engineering applications where strength and durability are critical factors. It has been determined that the mechanical property changes of needleleaved and broad-leaved wood samples subjected to thermal treatment at both 175 °C and 205 °C in the same chamber are similar. It has been suggested that thermal treatment of both wood types could be carried out at a slightly higher chamber temperature (above 175 °C), thereby achieving a much closer thermal treatment effect for both wood types and potentially achieving significant energy savings.