Analysis of the interaction between internal porosity and oriented strand board performance using X-ray computed tomography

The internal structure of oriented strand board (OSB) is made of a large number of voids. This results from the complexity of strand distribution within the panel and impacts panel performance greatly. In this research, X-ray microcomputer tomography was used to investigate the void characteristics of OSB panels with different structures. The results indicated that OSB panels have a porosity profile opposite to that of density. Unidirectionally oriented homogeneous boards showed slightly higher total porosity, a steeper porosity profile, and higher void size than other three-layer boards. Still, there was no significant difference between them. Although the changes in bending properties resulted from changes in core layer strand orientation, the slight difference in internal bond and water absorption rate was caused by the narrower void distribution and a larger void size. Panels containing a mixture of black spruce and aspen strands had a higher porosity, a steeper porosity profile, and a small void size compared to panels with black spruce strands. This resulted in better bending properties, worse internal bonding, and a lower water absorption rate and thickness swelling. Thus, the internal bond, water absorption rate, and thickness swelling of the panels with a mixed spruce-aspen core layer decreased with an increase in core layer proportion. An opposite trend was observed for panels with a black spruce core layer.