Ciência Florestal (Jan 2016)
INFLUÊNCIA DA TEMPERATURA NA RESISTÊNCIA E NO MÓDULO DE ELASTICIDADE EM MADEIRA DE HÍBRIDOS DE EUCALIPTOS
Abstract
This paper deals with the influence of temperature in a range from 20 °C to 240 °C, in the physical properties of wood: humidity and specific and mechanical masses: strength and modulus of elasticity for the parallel compression to the fibers. The experimental program was performed with 78 specimens of hybrids of Eucalyptus grandis x Eucalyptus urophylla with mean apparent specific gravity of 671 kg/m 3 and moisture content of 11.14%. The test procedures prescribed by NBR 7190 were followed. The results show a linear decrease in moisture content with increasing temperature up to 160°C. Two straight lines are noteworthy, the first one from 20°C to 65°C with slight decrease in moisture content, reaching 4% and the second one from 65°C to 160°C with the sharpest loss reaching 0% content of moisture. Above 160°C, the moisture content is zero, so that the wood loses only organic material, coming to lose 20% by weight when it reaches a temperature of 240°C. The specific mass remains practically constant until the temperature of 100°C. Temperature between 100°C to 240°C, the specific mass decreases linearly reaching 20 per cent. The strength to compression parallel to the fibers increases linearly with the temperature, reaching 19% at 100°C. Above this temperature, the behavior is inverse, with linear decrease until the temperature of 180°C. From 180°C the compression strength decreases reaching the temperature of 240°C at 32% lower than the resistance at the temperature of 20 ºC. As the modulus of elasticity decreases, it only increases the temperature. Up to the temperature of 120°C, it has a very slight linear decrease of around 8 per cent. However, between 120°C and 200°C the decrease is also linear, but more accentuated, reaching 38 per cent.
