Structural Properties of Oriented Wood Strand Composite: Effect of Strand Orientation and Modeling Prediction

This paper first examined the effect of wood strand orientation on the flexural properties of oriented wood strand composites (OSB) under different engineering stress modes, and second, investigated the applicability of the rule of mixtures in conjunction with the theory of elasticity for predicting the properties of OSB. The results showed that the performance of OSB was closely related to the loading directions and stress modes: The flexural strength and stiffness under both flat and edgewise bending loads consistently decreased with increasing angles between the applied load and longitudinal direction of orientation of strands, but that under flat bending being much more significant. Panel shear at 45° loading angle resulted in higher strength compared to other loading angles tested, indicating an occurrence of diagonal shear stresses. In conjunction with the numerical results from image analysis of the structure of OSB, and the oriented elasticity and stress algorithms, the models for theoretically predicting the strength and stiffness of OSB under various loading angles were derived with a good estimate under bending and panel shear loads, implying that OSB can be treated as a composite and its properties may be modeled by the rule of mixtures by suitable development, even though OSB has a very high volume fraction of wood strands (0.979) and correspondingly very low volume fraction of resin (0.021).