Method to compute fiber directions in wood from computed tomography images

Abstract

This paper describes a new method, called the CT-direction method, in which the fiber directions in wood in three-dimensional space are calculated from the pixel information on a series of two-dimensional computed tomography images. Local fiber directions are calculated from the principal directions of inertia of measurement spheres distributed throughout the body of the wood object. The calculated fiber directions are probably due to density streaks in the material, such as fiber bundles, which are directed in the fiber direction, and not the density of individual fibers, which are too small to be detected. The fiber directions vary locally, and density streaks from knots, growth rings, and compression wood influence the results, which adds spread to the results. The fiber directions are presented as spiral grain angles and conical angles and are compared with spiral grain angles measured with the tracheid-effect method. The comparisons show that the CT-direction method is a nondestructive way to measure fiber directions locally and in the interior of the body of a piece of wood.