Combining X-ray CT and DIC to understand the bending strength of OSB

Oriented strand board (OSB) is an important engineered wood product manufactured through bonding of wood strands in cross-oriented layers. The bending strength, one of the crucial properties for loadbearing material, of OSB strongly depends on its structural characteristics. To understand the bending strength of OSB, strain dis-tribution was continuously monitored during a three-point bending test using digital image correlation (DIC) and internal structure was recorded before and after bending using X-ray computed tomography (X-ray CT) respectively. Specimens were cut either along the length (L specimens) or width (W specimens) of OSB panels. For all specimens, strain accumulation mainly seemed to occur in the top and bottom layers and then propagate along or across the central layer. Structural changes in the top and bottom layers of L specimens was either strand delamination or snap off, while only snap off is found in W specimens. This is the main reason of high modulus of elasticity (MOE) and modulus of rupture (MOR) of L specimens in comparison to W specimens. High MOR of the specimens is attributed to strain propagation along the central layer, which can absorb energy from loading. Strain propagation across the central layer causes low MOR, resulting from failure of small strands and delamination in the central layer. Different modes of structural change lead to large variability of MOE, MOR and deformation of the specimens even cut from a single OSB panel. Understanding the bending strength contributes to optimizing the production and application of OSB.