A study on the fracture characteristics of unmodified and chemically modified Scots pine (Pinus sylvestris) is presented. The investigated material consisted of small-dimension sawn timber originating from young logs (thinnings), aged 30–40 years. The modified samples were acetylated with acetic anhydride in an industrial scale process without the use of any catalyst, reaching an acetyl content of approximately 20%. Clear wood specimens, consisting of either heartwood or sapwood, were extracted and conditioned to equilibrium at a relative humidity of 60% and a temperature of 20 °C. The fracture energy for mode I loading in tension perpendicular to the grain was determined using single edge notched beam (SENB) specimens, subjected to three-point bending. Additionally, the modulus of elasticity along the grain and the tensile strength perpendicular to the grain were determined for sapwood specimens. The findings demonstrated a significant decrease (between 36 and 50%) in the fracture energy for the acetylated specimens, compared to the unmodified specimens. No significant effect of the acetylation process on the modulus of elasticity, nor on the tensile strength could be concluded. This study indicates that the acetylation process used results in an increased brittleness for Scots pine. Further studies are needed to analyse why the fracture energy is impaired, and to examine whether and how current timber engineering design provisions can or should be revised to account for the increased brittleness of acetylated Scots pine.

中文翻译：

---

乙酰化年轻苏格兰松树的断裂特征

未经改性和化学改性的樟子松（樟子松）的断裂特性研究。） 被呈现。被调查的材料包括年龄在30至40岁的小尺寸锯材，它们来自年轻的原木（稀料）。在不使用任何催化剂的情况下，在工业规模的方法中用乙酸酐将改性的样品乙酰化，达到约20％的乙酰基含量。提取由心材或边材组成的透明木材标本，并在60％的相对湿度和20°C的温度下调节至平衡状态。使用单边切口梁（SENB）样品，经过三点弯曲，确定了垂直于晶粒的I型加载的断裂能。另外，对于边材样品，确定了沿晶粒的弹性模量和垂直于晶粒的拉伸强度。研究结果表明，与未改性样品相比，乙酰化样品的断裂能显着降低（36％至50％）。没有得出乙酰化过程对弹性模量或拉伸强度没有显着影响的结论。该研究表明，所用的乙酰化过程导致苏格兰松树的脆性增加。需要进一步的研究来分析为什么破坏能量会受到损害，并检查是否以及如何修改当前的木材工程设计规定，以解决乙酰化樟子松脆性增加的问题。也不能得出抗张强度。该研究表明，所用的乙酰化过程导致苏格兰松树的脆性增加。需要进一步的研究来分析为什么破坏能量会受到损害，并检查是否以及如何修改当前的木材工程设计规定，以解决乙酰化樟子松脆性增加的问题。也不能得出抗张强度。该研究表明，所用的乙酰化过程导致苏格兰松树的脆性增加。需要进行进一步的研究以分析为什么破坏能量会受到损害，并检查是否可以以及应该如何修订当前的木材工程设计规定，以解决乙酰化樟子松脆性增加的问题。