宽温度含水率域桦木横纹拉伸蠕变研究

木材受力会蠕变变形,在实际使用过程中,其蠕变变形往往受环境温度和湿度的双重影响。而精确控制试件含水率一直是研究难点。通过对试件包裹耐高温薄膜(PVDC)并采用带湿度附件的DMA精准控制试件含水率,在宽温度范围内对宽含水率范围的桦木(Betula pendula)进行了横纹拉伸蠕变性能研究。结果表明:桦木横纹拉伸蠕变的瞬时柔量和蠕变柔量均随着温度和含水率的变大而增大,在高温高含水率条件下与低温低含水率条件下有数量级之差。在一定温度和一定含水率水平组合下,桦木横纹拉伸蠕变存在突增的现象,这一现象与玻璃化转变温度有关。温度和含水率对于桦木横纹拉伸蠕变起着一种复杂的交互作用。

Transverse Tensile Creep of Birch in Wider Temperature Range and Moisture Content Range

Wood will creep and deform under stress,while in actual use,its creep deformation is often affected by the dual effects of ambient temperature and humidity.However,it has always been difficult to accurately control the moisture content of the specimens in the research.In this study,the specimen was wrapped with a polyvinylidene chloride(PVDC)film and DMA with a humidity accessory was used to precisely control the moisture content of the specimen.The transverse tensile creep properties of birch(Betula pendula)in a wide range of moisture content were studied in a wide range of temperature.The results showed that the instantaneous and creep compliances of birch’s transverse tensile creep increased with the increasing of temperature and moisture content,and there was an order of magnitude difference between high temperature and high moisture content conditions and low temperature and low moisture content conditions.Under a certain combination of temperature and moisture content,the transverse tensile creep of birch increased abruptly,which was related to its glass transition temperature.Temperature and moisture content had a complex interaction on the transverse creep of birch.