| In 2007, more than 9.3 million acres were burnt by wildfire with a 10-year average of 6.4 million acres. Thus there is a considerable amount of wood potentially available as raw material for composites from recently fire-impacted sites. Such utilization, however, is currently unexploited. The objectives of this research were to study the feasibility of using fire-impacted trees for oriented strand boards (OSB) production and to model the physical and mechanical behavior of OSB. Trees that were variously impacted by forest fire were harvested, flaked, and converted to OSB. Bark of the respective trees was added up to 20% by weight to the OSB furnish. Mechanical and physical tests of the strands, bark, and OSB were performed. Modeling of OSB sorption behaviors was conducted under cyclic humidity environments. A composite model based on micromechanics and laminate theories was also developed to discern contributions of constituent materials, i.e., strands and bark from fire-impacted trees, to the OSB stiffness. Results indicate that the performance properties of OSB made of fire-exposed timber were similar to that made of non-exposed timber. Analyses of wood strands flaked from fire-impacted (red pine) trees further revealed that their bending properties and density were not significantly different compared to the strands obtained from unburnt trees. The cyclic changes of the moisture content and thickness swelling of OSB were accurately characterized by power-law and exponential models. Evidenced from the fitted coefficients of both models, bark addition did not affect the rate but the amount of moisture content and thickness changes of OSB. The composite model developed was found adequate in predicting the bending stiffness of both all-wood and hybrid (wood and bark) OSB. Overall, results from this research suggest that burnt timber is a promising alternative bio-feedstock for commercial OSB production. Findings from this study could also be extended to model, predict, and engineer properties of wood-based composites in screening or utilizing alternative raw materials. |
