Effect of moisture and temperature on some mechanical properties of beechwood

Abstract

The effect of moisture and temperature on beechwood static MOE, MOR and stress at proportional limit in bending was tested. The experiment was performed at wood moisture contents of 0, 10, 17 and 24 %. and maximum MC, and at temperatures of 20, 40, 60, 80 and 100 degrees C, in radial and tangential directions. The highest MOE, (12880 MPa) was measured for oven-dry wood in radial direction. MOE decreased with the increase in wood moisture and temperature by about 4 times. It was proved that MOE was in functional linear correlation with wood hygroscopic moisture and the temperature of moist wood. MOE did not change with moisture above the hygroscopicity limit or with temperature when the wood was dry. The increase of moisture within the hygroscopic range by 1 % caused the decrease in MOE by 1.3 to 3.3 %, depending on temperature and anatomic direction, while the temperature increase by 1 degrees C caused the decrease of MOE by 0.2 to 0.6 %, depending on wood moisture. Oven-dry beechwood MOR is 150 to 160 MPa. MOR decreased with the increase of hygroscopic moisture by the exponential law, while the effect of temperature was linear. The increase of moisture in the hygroscopic range by 1 % caused the decrease of MOR by 2.1 to 7.1 %, and the increase of temperature by 1 degrees C caused its decrease by 0.4 to 0.6 %, for both anatomic directions. The stress at proportional limit ranged between 42 and 70 % of the value of MOR, and the effect of moisture and temperature on its change was generally synchronic with their effect on MOR.