Evaluation of thermally modified beech and spruce wood and their properties by FT-NIR spectroscopy

Quality assessment of thermally modified spruce (Picea abies (L.) Karst) and beech (Fagus sylvatica L.) wood and of the corresponding reference samples was carried out by means of non-destructive FT-NIR spectroscopic measurements and PLS regression. Oven-dry and basic density as well as MOE and MOR determined by 3-point bending tests were evaluated. The focus was put on specimens produced from material that had been thermally modified in an industrial scale kiln. Modelling results range from poor to very good. The results of the spectra taken from the spruce samples resulted in better prediction results than the spectra of the beech samples. This could be due to different proveniences or variation in the industrial modification process. The results indicate that FT-NIR surface measurements of sound thermally modified wood samples could be applied to evaluate several characteristics before and after the modification process. The method could be used for screening during pre-sorting of thermally modified wood.