Strands For Wood Composites: Mechanics & NIRS Based Nondestructive Testing

Abstract

Improvements in silvicultural techniques have allowed for rapid growth and shorter rotation age of southern pine species utilized for structural wood components. However, the rapid growth results in lumber consisting largely of juvenile wood. Juvenile wood is not desirable for solid lumber products as it possess lower strength qualities than mature wood. Therefore smaller diameter trees yielding lower quality wood have been effectively utilized in production of composite products such as oriented strand board (OSB) and oriented strand lumber (OSL). By using smaller diameter, short rotation plantation trees, composite products reduce the stress placed on mature stands and allow land owners to generate income from forests in shorter intervals. However, greater environmental and economical benefits could be realized through better utilization of OSB material streams. Better utilization will result in lower resin consumption, lower transportation cost, and reduced stress on existing forest stands. Currently OSB is produced with little regard for wood flake properties, with all flakes considered equivalent in mechanical properties. By effectively utilizing flakes throughout the OSB profile it will be possible to engineer high strength lightweight composites. It is the aim of this project to utilize NIR as a method to characterize flakes based on predicted mechanical properties (stiffness and strength). NIR techniques are proven effective at rapidly predicting wood quality and strength. Industry has not yet embraced NIR spectroscopy as a method for nondestructive testing. However, applied research such as this project may generate interest in application of NIR techniques to wood composite manufacturing such as oriented strandboard or oriented strand lumber.