Consolidation of Flakeboard Mats Under Theoretical Laboratory Pressing and Simulated Industrial Pressing
Keywords:Densification, consolidation, density profile, compression, <i>in-situ</i> measurement, flake-board, pressing, radiation, moisture, bonding, resin, unsteady state
AbstractTo achieve a more fundamental understanding of material behavior during the pressing process, a radiation-based system for measuring density of wood composite mats during consolidation is used to build in-situ cross-sectional density distributions of flakeboard mats with pressing time. The fundamentals of densification within flakeboard mats during hot and cold pressing are discussed in this paper. The pressing schedules included theoretical laboratory pressing schedules and schedules simulating industrial pressing. All tests were conducted at either ambient or 204°C temperature. The results include stress relaxation of flakeboard mats during cold and hot pressing, stress-strain behavior, in-situ density-strain behavior, and in-situ cross-sectional density distributions of flakeboard mats with pressing time. Results of laboratory studies indicate that the stress relaxation during hot pressing after the press reached final position was much quicker than during cold pressing. The observed stress-strain responses of flakeboard mats in hot pressing and cold pressing were similar, characterized by a long stress plateau followed by a rapid increase in stress and an immediate fall-down after the press reached final position. The process to simulate the industry operation resulted in another stress plateau. The stress-strain responses of flakeboard mats were characterized by a long stress plateau followed by a rapid increase in stress, and an additional high stress plateau followed by an immediate fall-down after the press reached final position. There was no clear indication that the maximum gas pressure attained is affected by press closing time.
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