The orthotropic and temperature-dependent nature of the mechanical properties of wood is well recognized. However, past studies of mechanical properties at elevated temperatures are either limited to temperatures below 200 °C or focus only on the direction parallel to grain. The effect of time-dependent pyrolysis during measurement is often neglected. This paper presents a novel method for determining elastic modulus at high temperatures and thermal expansion coefficient in different orthotropic directions via Dynamic Mechanical-Thermal Analyser (DMTA). The method allows for drying, drying verification, and measurement in one chamber, eliminating the possibility of moisture reabsorption from ambient air. The repeatable measurements can be carried out in temperatures up to 325°C, adequate for observing time-dependent pyrolysis during measurement. Results of the measurements of Norway Spruce provide data of its mechanical response at temperature range previously not explored widely, as well as in the orthotropic direction. Time-dependent behaviour was observed in the thermal expansion and shrinkage experiment, where above 250°C the amount of shrinkage depends on heating rate. At such temperature, elastic moduli measurement also shows time dependence, where longer heating at certain temperature slightly increases the measured elastic modulus. Additionally, bilinear regression of the relationship between elastic moduli and temperature shows quantitatively good fit. Numerical simulation of the DMTA temperature history and wood chemical components mass losses show the onset of shrinkage and onset of hemicellulose mass loss occurring at around the same time, while decomposition of cellulose correlate with the sudden loss of elastic moduli.

木材的机械性能具有正交各向异性和温度依赖性。然而，过去对高温下的机械性能的研究要么限于低于200°C的温度，要么仅关注与晶粒平行的方向。在测量过程中，时间依赖性热解的影响通常被忽略。本文提出了一种通过动态机械热分析仪（DMTA）确定高温下的弹性模量和不同正交各向异性方向上的热膨胀系数的新方法。该方法允许在一个室内进行干燥，干燥验证和测量，从而消除了水分从周围空气中重新吸收的可能性。可重复测量可在高达325°C的温度下进行，足以观察到测量过程中随时间变化的热解。挪威云杉的测量结果提供了其在以前未广泛探索的温度范围内以及在正交各向异性方向上的机械响应的数据。在热膨胀和收缩实验中观察到随时间变化的行为，其中高于250°C时，收缩量取决于加热速率。在这样的温度下，弹性模量测量还显示出时间依赖性，其中在特定温度下更长的加热会稍微增加所测得的弹性模量。此外，弹性模量与温度之间关系的双线性回归显示出良好的定量拟合。DMTA温度历史和木材化学成分质量损失的数值模拟显示了收缩的发生和半纤维素质量损失的发生在大约同一时间发生，