竹材及杨木单板在湿热环境下的湿膨胀性能差异

竹材杨木复合层积材在使用过程中会因环境湿度和温度的变化而产生一定的形变，甚至功能失效。对竹材和杨木的湿膨胀系数在各个方向的差异进行研究，可为竹材杨木复合材料的合理设计提供依据。笔者采用电阻应变片法，研究竹材和杨木单板在恒温条件下除湿和增湿处理不同阶段的应变，分析了竹材和杨木的不同方向湿膨胀系数。结果表明：竹材和杨木在纵横两方向上的湿膨胀有着较大差异。这种差异在常温常湿下最小；湿度下降阶段，杨木单板的纵向及横向湿膨胀系数为竹材的2倍以上，两者复合后杨木形变量较大，竹材的应变具明显的吸湿滞后。由于吸湿膨胀系数和吸湿滞后的影响，在湿度变化时，会出现除湿时向杨木方向的纵向弯曲，吸湿膨胀时会出现向竹材面的纵向弯曲现象。

Difference of hygroscopic expansion between poplar veneer and bamboo strip under the hygrothermal environment

To understand the hygroscopic coefficient different on the bamboo and poplar,the hygroscopic coefficient of Moso bamboo strip and poplar veneer in different humidity process were tested by the resistant strain sheet.The results showed that the hygroscopic expansion coefficients of poplar in longitudinal and transverse dimension are more than 2 times those of bamboo in the period of dehumidifying.Bamboo displayed an obvious lag response to environmental temperature and relative humidity change compared with ...