Effect of test temperature on creep behavior of heat treated of Velvet Maple

Extensive application of heat treated wood in exterior uses with high relative humidity and high temperature circumstances, necessitates the study of mechanical and creep behavior of them at such situations. The general objective of the present study was investigating the effect of test temperature on creep behavior of heat treated velvet maple wood. Heat treatment was conducted on oven dried maple wood samples at three temperature levels of 160, 175 and 190oC. Four-point static flexural test was conducted for determination of the required load level for creep test in three replications at each treatment temperature levels. For conducting creep tests, three levels of test temperature of 21, 40 and 60oC and duration of 65 hours were considered. Results of flexural test showed that heat treatment led to decreasing the rupture modulus compared to the control one; however, the elastic modulus did not change significantly. Results of creep test showed that with increasing test temperature, instantaneous and creep compliance values increased. With increasing treatment temperature, creep compliance was increased as well. Anti-creep efficiency ratio for evaluating the effect of test temperature on creep value at different levels of treatment showed that generally heat treatment led to decreasing the creep strength compared to the control ones. Heat treatment at temperature of 160oC led to in improvement in creep behavior at higher test temperature, in which the reason was attributed to increase of cellulose crystallinity and lignin condensation reaction, in turn led to lower plasticization of wood at higher test temperature.