Laminated veneer lumber (LVL) is an important engineered wood product. Internal structural changes have a substantial influence on the mechanical performance of LVL. To investigate the relationship between the internal structural changes and the compressive strength, poplar LVL layering is manufactured by taking into account the veneer lathe checks, namely lathe checks both facing inwards (TLLT), lathe checks both oriented outwards (LTTL) and lathe checks in one layer facing outwards (LTLT). Macroscopic compressive strength of the samples is measured using a universal testing machine. Microscopic internal structural changes are periodically recorded with X-ray CT when the samples are compressed using a load cell. The results show that the compressive strength of LTLT is significantly higher than that of LTTL and TLLT types of LVL. During the compression test, density increase in the samples is non-homogenous. There is a minor increase in density of the glue line, while this is larger in regions with a low density. Density increase is mainly induced by collapse of large vessels. However, the presence of phenol formaldehyde resin can enhance the resistance of vessels against collapse. Structural changes, i.e., vessels collapse and collapse propagation, are likely to occur in locally heterogeneous regions. Propagation of collapsed vessels is more frequently observed in regions where large vessels are contiguous.

中文翻译：

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结构变化对LVL抗压强度的影响

层压单板木材 (LVL) 是一种重要的工程木制品。内部结构变化对 LVL 的机械性能有重大影响。为了研究内部结构变化与抗压强度之间的关系，通过考虑单板车床检查制造杨木 LVL 分层，即车床检查双面向内 (TLLT)、车床检查双外向 (LTTL) 和车床检查在一层朝外 (LTLT)。使用万能试验机测量样品的宏观抗压强度。当使用称重传感器压缩样品时，X 射线 CT 会定期记录微观内部结构变化。结果表明，LTLT 的抗压强度明显高于 LTTL 和 TLLT 类型的 LVL。在压缩试验期间，样品的密度增加是不均匀的。胶层的密度略有增加，而在密度低的区域则更大。密度增加主要是由大血管塌陷引起的。然而，酚醛树脂的存在可以增强血管的抗塌陷能力。结构变化，即血管塌陷和塌陷传播，很可能发生在局部异质区域。在大血管相邻的区域更常观察到塌陷血管的传播。酚醛树脂的存在可以增强血管的抗塌陷能力。结构变化，即血管塌陷和塌陷传播，很可能发生在局部异质区域。在大血管相邻的区域更常观察到塌陷血管的传播。酚醛树脂的存在可以增强血管的抗塌陷能力。结构变化，即血管塌陷和塌陷传播，很可能发生在局部异质区域。在大血管相邻的区域更常观察到塌陷血管的传播。