An optical technique for determination of layer thickness swell of MDF and OSB

e have been studying the phenomenon of thickness swell in woodbased composites as part of our overall research program to address composite product manufacture and performance (Xu and Winistorfer 1995a, 1995b; Wang and Winistorfer 2000a, 2001). We purport that one of the key variables in understanding the thickness swell phenomenon is recognition of the density profile through the panel thickness. The density profile results from the complex interaction of heat, pressure, and temperature and their combined impact on the consolidation characteristics of the mat during pressing. The interaction of these variables results in non-uniform stress development and relaxation through the thickness of the mat during pressing. We have designed an in situ system for measuring the density profile of the mat during pressing (Winistorfer et al. 1998, Wang and Winistorfer 2000b) and are studying the relationship between consolidation characteristics and panel performance, particularly thickness swell. Improved dimensional stability performance, primarily thickness swell, would enhance performance of current panel products inawiderangeofapplications. Suchsland (1973) suggested that the density profile of particleboard samples would lead to internal swelling stresses as the low density layers in the panel re-