Effects of thermal treatment on the mechanical properties of larch (Larix gmelinii) and red oak (Quercus rubra) wood cell walls via nanoindentation

Thermally treated wood is widely used for construction, furniture, and flooring because it has better dimensional stability in outdoor conditions. There is a close relationship between the mechanical properties of thermally treated wood cell walls and the performance of its products. The hardness (H) and reduced elastic modulus (Er) of larch (Larix gmelinii) and red oak (Quercus rubra) wood cell walls were investigated via nanoindentation. The results showed that the larch and red oak wood specimens had different nanomechanical properties. The Er in the larch wood initially increased with a maximum value of 22.4 GPa at 225 °C, then rapidly decreased after 300 °C with a minimum value of 5.7 GPa at 350 °C. The Er in the red oak wood appeared to have a mild decline. The H in both wood species visibly increased with the thermal treatments due to the reduction of organic wood polymers and the increase of inorganic carbon materials.