The article offers a perspective on how thermal-modification affects the impact bending strength of five different wood species, an aspect that has not received as much attention as the well-studied static load behavior of thermally-modified timber (TMT). Since the TMTs are mainly employed as outdoor materials, where they may encounter impact forces, a comparative investigation into the flexibility and strength of these materials under impact is useful. This article evaluates different aspects of the TMT, such as deflection, strain in the impact region, the maximum force needed to initiate cracks, and the energy required for rupture. Wood planks from ash, beech, larch, oak, and spruce were thermally modified at 180 and 220 °C. They were cut into test specimens, while a separate set of unmodified specimens from each wood species served as the reference group. The specimens were subjected to an impact 3-point bending test, and an ultra-high-speed camera meticulously recorded the results. The images were processed by the digital image correlation (DIC) method to determine the deflection and strain distribution of the beams during the impact test. The deflection, maximum force, maximum longitudinal strain, and required work for rupture of each group were determined. The results showed that thermal-modification decreases the wood deflection and maximum longitudinal strain by approximately 50 %. In addition, the impact bending strength decreased by nearly 60 %. However, the impact bending strength did not exhibit a statistically significant decrease at 180 °C; in some cases, it even increased.

中文翻译：

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热改性木材的冲击弯曲强度

该文章提出了热改性如何影响五种不同木材树种的冲击弯曲强度的观点，这一方面尚未像热改性木材 (TMT) 的静载荷行为得到充分研究那样受到足够的关注。由于 TMT 主要用作户外材料，可能会遇到冲击力，因此对这些材料在冲击下的柔韧性和强度进行比较研究是有用的。本文评估了 TMT 的不同方面，例如变形、冲击区域的应变、引发裂纹所需的最大力以及破裂所需的能量。由白蜡木、山毛榉、落叶松、橡木和云杉制成的木板在 180 和 220 °C 的温度下进行热改性。它们被切成测试样本，而来自每个木材品种的一组单独的未修改样本作为参考组。对样品进行冲击三点弯曲测试，超高速摄像机仔细记录结果。通过数字图像相关（DIC）方法对图像进行处理，以确定冲击试验期间梁的挠度和应变分布。确定每组的偏转、最大力、最大纵向应变和断裂所需的功。结果表明，热改性可将木材挠度和最大纵向应变降低约 50%。此外，冲击弯曲强度下降了近60%。然而，在180℃时冲击弯曲强度并没有表现出统计上显着的下降；在某些情况下，它甚至有所增加。