BENDING PROPERTIES OF SUGI (JAPANESE CEDER) IN HEATING BELOW 180-DEGREES C

The modulus of elasticity and bending strenght of wood decrease on heating and increase on cooling. At a constant moisture content (5% less at the surface) and below 180-degrees-C in an oven, the bending properties of Japanese ceder (Cryptomeria japonica D. Don), with clear wood specimens, sized 25 mm square and 350 mm span, were tested. The change of modulus of elasticity and bending strength were started at 50-degrees-C and approximately linearly decreased with temperature, but a little change was observed in 75-95-degrees-C. In the first stage at low temperatures ratio of the change was more remarkable than the next stage, because probably losing moisture. The effect of the temperature rise on the modulus of elasticity and bending strenght showed 30% and 45% loss, respectively, with mean value at 180-degrees-C, and heartwood showed a difference from sapwood above 95-degrees-C and decreased 10% at 180-degrees-C. The ratio of the modulus of elasticity at room temperature versus at elevated temperatures was constant at each elevated temperature. The relation between bending strength and modulus of elasticity at elevated temperature showed a good regression coefficiet which was the same in unheated wood. The maximum deflection and proportional limit were linearly decreased with temperature rise and indicated a degradation of wood.