The Influence of Fines Content and Panel Density on Properties of Mixed Hardwood Oriented Strandboard
Keywords:Mixed hardwood, OSB, linear expansion, effective modulus, fines, modeling
Single- and three-layer mixed hardwood oriented strandboard (OSB) with various wood fines contents and panel densities were manufactured using phenol-formaldehyde (PF) resin as binder. The effects of fines level and density on the panel properties were studied. Mathematical models based on lamination theories were used to predict properties of three-layer panels, including effective modulus (EM), linear expansion (LE), and swelling stresses using single-layer data as model input. The model's prediction was compared with actual experimental data.
For single-layer panels, parallel bending modulus and strength decreased, while the perpendicular values increased as fines increased in the panels. LE and thickness swelling increased with the increase of fines contents. Regression analysis indicated that bending properties and LE were highly correlated with fines content and panel density. The results of three-layer boards with a small fixed amount of fines in the face layers showed that the bending properties varied little in the parallel direction and decreased in the perpendicular direction as fines in the core layer increased. Parallel LE decreased and the perpendicular value increased with the increase of fines in the core layer. Predicted EM and LE agreed well with the experimental data. Shifting a certain amount of fines from core to face layers led to more balanced panel properties along the two principal directions. Predicted swelling stresses decreased with the increase of fines levels in the boards.
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