采用准静态试验和超声波法对热处理后的山毛榉和桦木进行表征。

Department of Material Science and Process Engineering, Institute of Wood Technology and Renewable Materials, University of Natural Resources and Life Sciences, Vienna, Konrad Lorenz-Straße 24, 3430, Tulln an der Donau, Austria.

Department of Engineering for Innovation, University of Salento, Via per Monteroni, 73100, Lecce, Italy.

Sci Rep. 2023 Apr 18;13(1):6348. doi: 10.1038/s41598-023-33054-w.

Wood, being renewable and highly abundant material, with excellent high specific strength and stiffness, has received increasing attention to be used in high performance applications such as the structural element of a battery case in an electric vehicle. For a successful implementation of wood in the automotive sector, it is, therefore, crucial to understand the behaviour of wood during and after temperature exposure and in the event of fire with the presence/absence of oxygen. In this study, the mechanical properties of thermally modified and unmodified European beech and birch in air and nitrogen environments at six different treatment intensities were characterised using compression tests, tensile tests, shear tests and Poisson's ratio tests. Further, the elastic properties of these wood species were quantified using the ultrasound measurements. The obtained strength and stiffness exhibited mild improvement upon moderate temperature treatment (200 °C), followed by a decrease at elevated temperature levels. This improvement was somewhat more pronounced under nitrogen treatment than under air treatment conditions. Nevertheless, a more noticeable decrease in the material performance was observed in beech compared to birch, occurring at earlier stages of modifications. This study confirms the tension-compression asymmetry of beech and birch where higher Young's moduli were obtained from tensile than from compression tests for reference and thermally treated beech and birch. The shear moduli obtained from ultrasound for birch were comparable to those obtained from quasi-static tests, whereas there was an overestimation of approximately 11-59% for the shear modulus of beech compared to quasi-static tests. Poisson's ratios from ultrasound tests corresponded well with those from quasi-static tests for untreated beech and birch, but not for thermally modified samples. The Saint-Venant model can satisfactorily predict the shear moduli of untreated and treated beech wood.

木材是一种可再生且丰富的材料，具有优异的高比强度和比刚度，因此越来越受到关注，可以用于高性能应用，例如电动汽车电池外壳的结构元件。为了在汽车领域成功应用木材，因此，了解木材在温度暴露期间和之后以及在存在/不存在氧气的情况下发生火灾时的行为至关重要。在这项研究中，使用压缩试验、拉伸试验、剪切试验和泊松比试验对空气和氮气环境中的热处理和未处理的欧洲山毛榉和桦木在六种不同处理强度下的机械性能进行了表征。此外，还使用超声波测量法量化了这些木材的弹性特性。在中等温度处理（200°C）下，获得的强度和刚度略有提高，随后在高温下下降。在氮气处理下，这种改善比在空气处理条件下更为明显。然而，与桦木相比，在更早的改性阶段，山毛榉的材料性能下降更为明显。这项研究证实了山毛榉和桦木的拉伸压缩不对称性，即参考和热处理的山毛榉和桦木的拉伸试验得到的杨氏模量高于压缩试验。从超声波获得的桦木剪切模量与准静态试验获得的剪切模量相当，而与准静态试验相比，桦木的剪切模量高估了约 11-59%。从超声波试验获得的泊松比与未经处理的山毛榉和桦木的准静态试验相当，但与热处理后的样品不相当。圣维南模型可以很好地预测未经处理和处理后的山毛榉木材的剪切模量。