Microtomography of Cellulosic Structures, 1998 Process & Product Quality Conference Proceedings

The performance of wood composite materials are manipulated through changes in composition and process variables. Microstructural features such as fiber orientation and void structure are known to be spatially variable. X-ray microtomography techniques were used to measure three-dimensional microstructural features in solid wood, paper, and wood based composites at resolutions of 1.2 mm to 6.75 mm per voxel side. The microtomogra-phy was conducted at the X2B beamline built and run by Exxon Research and Engineering at the Department of Energy managed National Synchrotron Light Source (NSLS). Beam energy levels ranged from 8.5 keV to 19 keV, with lower energy levels giving improved signal/noise ratios. Measurement of a single specimen required 2 to 6 hours, with increased times necessary for higher resolutions. Reconstructed three-dimensional data fields of x-ray absorption were used to measure internal features such as fiber curl, inter-fiber void volumes (related to density/grammage variation), and resin impregnation depths in three dimensions with no sectioning artifacts. Technique limitations include small specimen size and the complexity of data analysis and interpretation using existing image analysis based techniques.