College of Material Engineering , Fujian Agriculture and Forestry University , 350108 Fuzhou , China.
New Zealand School of Forestry , University of Canterbury , Private Bag 4800 , 8140 Christchurch , New Zealand.
Biomacromolecules. 2019 Aug 12;20(8):3191-3199. doi: 10.1021/acs.biomac.9b00808. Epub 2019 Jul 31.
To measure growth strain in wood using Raman spectroscopy, we investigated the Raman spectra of rewetted (water-saturated) and green wood during tensile tests. Partial least squares models to predict the tensile strain were built from the Raman spectra. The best model could predict the tensile strain with a root mean square error of 427.5 με. Apart from the widely reported band shift at 1095 cm upon mechanical strain, spectral changes at 1420, 1120, 895, and 456 cm were identified. The assignments of these bands were discussed in relation to the molecular deformation of cellulose. The band shift rates during tensile tests were -3.06 and -2.15 cm/% for rewetted and green wood, respectively. We successfully detected the release of the molecular growth strain in green eucalyptus wood with Raman spectroscopy by observing band shifts of the 1095 cm signal. Further, there was a moderate correlation ( = 0.48) between the growth strain measured with strain gauges and the 1095 cm band position. The precision of the prediction of growth strain using Raman spectroscopy was negatively affected by variation attributed to the inhomogeneity of wood on the millimeter scale and instrumental instability.
为了使用拉曼光谱测量木材的生长应变，我们研究了拉伸试验过程中重新润湿（水饱和）和绿色木材的拉曼光谱。从拉曼光谱中建立了预测拉伸应变的偏最小二乘模型。最佳模型可以以 427.5 με 的均方根误差预测拉伸应变。除了机械应变时在 1095 cm 处广泛报道的带移动之外，还确定了在 1420、1120、895 和 456 cm 处的光谱变化。这些带的分配与纤维素的分子变形有关。在拉伸试验过程中，重新润湿和绿色木材的带移动率分别为-3.06 和-2.15 cm/%。通过观察 1095 cm 信号的带移动，我们成功地用拉曼光谱检测到绿色桉树木材中分子生长应变的释放。此外，应变计测量的生长应变与 1095 cm 带位置之间存在中度相关性（ = 0.48）。拉曼光谱法预测生长应变的精度受到木材毫米级不均匀性和仪器不稳定性引起的变化的负面影响。
