Microscopic swelling analysis of spruce wood in sorption cycle

Abstract

Depending on drying or humidification conditions, spruce wood tends respectively to shrink or swell, because of internal mechanical stresses that cause microscopic morphological changes. In the present paper, an experimental campaign is performed at the microscopic scale, in order to study the structural changes caused by relative humidity solicitations along the sorption cycle, for both early wood and latewood phases. That is why many specimens were scanned at different relative humidity levels using X-ray tomography. Relative humidity conditioning was successful by designing a specific device adapted to tomography. The obtained resolution using X-ray tomography was 3.3µm/pixel. After that, the reconstructed volumes were post-treated using adapted software to spruce wood, iMorph. Cell walls’ thicknesses and lumens’ diameters have been calculated at each humidity state. These results have given much better understanding of the localized phenomena that take place at the fiber’s scale.