Surface quality of planed tangential and radial sections of thermally modified Silver fir wood

Abstract

The quality of glued or coated wood largely depends on the strength of the bond between the adhesive or coating and the wood surface. The roughness of the surface plays a crucial role, as it significantly impacts both the wettability and the effectiveness of the bond. This study was carried out to provide information on the surface roughness of Abies alba (silver fir) planed after thermal modification, focusing on the anisotropic behavior of the material, particularly along the radial and tangential sections. Four groups of eight samples without defects were prepared. Half of the samples of each group presented clear tangential section while the other half presented clear radial ones. One group was used as control and the others were heated, applying three different temperatures 160 °C, 190 °C and 220 °C, at atmospheric pressure for 3 hours. The control and the three other heat-treated groups of samples were processed along the grain by a planer machine. 10 m/min feed speed was applied. Surface roughness measurements were performed with a stylus profilometer. A positive correlation was observed between the modification temperature and the roughness of the surface. It was noted that the radial section of natural wood presented greater roughness than the tangential one. For temperatures lower than 200 °C the roughness of both sections resulted almost equal, while above this temperature the roughness of the radial section increased over 20 % compared to the roughness of the tangential one. The information provided by this study is very important for the gluing and finishing processes that can be applied to thermally modified wood.

Keywords

• Anisotropy
• Silver fir
• surface roughness
• thermal modification
• wood surface