Thermo-hydro-mechanical (THM) processing can improve the intrinsic properties of wood, produce new materials, and give desired form and function to new applications. THM treatments change the mechanical properties of wood and may change its viscoelastic properties as well. Therefore, the objective of this study was to assess the viscoelastic properties of THM-treated wood at several humidity and load levels. To explore these changes, this study applied a THM treatment to beech (Fagus sylvatica L.) wood with steam (620 kPa) and heat (170 °C), followed by densification and increased temperature (200 °C) in a hot-press, which was then cooled while under pressure. Two initial specimen thicknesses before THM treatment were used to study the difference between density ratios. Specimens were tested in a humidity-controlled dynamic mechanical analyser (DMA) to apply creep stress with different loading levels (20% and 30% of expected modulus of rupture) and relative humidity levels (30%, 50%, and 65% RH). The creep compliance/recovery response was monitored, and dynamic moduli were measured before and after the application of creep stress. The loss modulus measured was highest for specimens tested at 65% RH and lowest in specimens tested at 30% RH, which is a direct result of the viscous response of the material. Increased damping of the specimens was also observed at higher RH, which is typical for wood products due to added moisture in the cell wall acting as a plasticizer to cell wall polymers. Like previous studies, THM treatment lowered the equilibrium moisture content (EMC) of densified wood specimens, which affected their mechanical performance. THM treatment yields higher strength and lower EMC, suggesting that this product could be suitable for structural applications where their service life is in an indoor environment. THM treatment also resulted in decreased creep compliance and recovery compliance as compared to control specimens.

热流体机械（THM）处理可以改善木材的固有特性，生产新材料，并为新应用提供所需的形式和功能。THM处理会改变木材的机械性能，也可能会改变其粘弹性。因此，本研究的目的是评估THM处理的木材在几种湿度和负荷水平下的粘弹性。为了探索这些变化，本研究对山毛榉（Fagus sylvatica）进行了THM处理L.）木材，先加蒸汽（620 kPa）和加热（170°C），然后在热压机中压实并提高温度（200°C），然后在加压下冷却。THM处理之前的两个初始样本厚度用于研究密度比之间的差异。在湿度控制的动态机械分析仪（DMA）中对样品进行测试，以施加不同载荷水平（预期断裂模量的20％和30％）和相对湿度水平（相对湿度30％，50％和65％）时的蠕变应力。监测蠕变柔度/恢复响应，并在施加蠕变应力之前和之后测量动态模量。在65％RH下测试的样品，测得的损耗模量最高，在30％RH下测试的样品，测得的损耗模量最低，这是材料粘性响应的直接结果。在较高的相对湿度下也观察到样品的阻尼增加，这是木制品的典型现象，这是由于孔壁中增加的水分充当了孔壁聚合物的增塑剂。像以前的研究一样，THM处理降低了致密化木材样品的平衡水分含量（EMC），从而影响了其机械性能。THM处理具有更高的强度和更低的EMC，表明该产品可能适用于使用寿命在室内环境中的结构应用。与对照样品相比，THM处理还导致蠕变顺从性和恢复顺从性降低。THM处理降低了致密化木材样品的平衡水分含量（EMC），从而影响了其机械性能。THM处理具有更高的强度和更低的EMC，表明该产品可能适用于使用寿命在室内环境中的结构应用。与对照样品相比，THM处理还导致蠕变顺从性和恢复顺从性降低。THM处理降低了致密化木材样品的平衡水分含量（EMC），从而影响了其机械性能。THM处理具有更高的强度和更低的EMC，表明该产品可能适用于使用寿命在室内环境中的结构应用。与对照样品相比，THM处理还导致蠕变顺从性和恢复顺从性降低。