In-Plane Dimensional Stability of Oriented Strand Panel: Effect of Processing Variables

Single-layer oriented strand panels were fabricated under a combination of three alignment levels, four densities, and two resin contents. Flake orientation, density gradient across panel thickness, linear expansion (LE), and bending properties were measured. Flake orientation was characterized with the von Mises distribution using mean flake angle and concentration parameter. It was shown that the shape of the LE-moisture content change curve varied with alignment level and test direction. The variation was attributed to whether the LE of a panel was controlled by transverse or longitudinal wood swelling along a particular test direction. Total LE from oven-dry to water-soak condition, modulus of elasticity (MOE), and modulus of rupture (MOR) varied significantly with flake orientation distribution and density. Effects of resin content at the levels used on LE, MOE, and MOR was relatively small and was more diversified. The LE, MOE, and MOR were correlated with the concentration parameter, density, resin content, and moisture content using a power form equation. The experimental data form a database of layer properties for modeling three-layer, cross-laminated oriented strandboards (OSBs) manufactured under hot pressing.