Monitoring Bond Strength Development in Particleboard During Pressing, Using Acousto-Ultrasonics
Keywords:
Adhesive cure, acousto-ultrasonics, internal bond, composite panels, hot-pressing, on-line sensing, nondestructive evaluationAbstract
As with other composite products, the quality of particleboard is sensitive to the manufacturing process. However, there is still no efficient on-line technique available to monitor and control the most critical process in particleboard manufacture, adhesive cure during pressing. The objective of this study was to develop a technique, using Acousto-Ultrasonics (AU), to nonintrusively monitor the bonding development of particleboard during hot-pressing. A series of tests were run in a 610-by 610-mm laboratory press, in which a tone-burst signal with a fixed frequency of 60 kHz was injected into one platen via a waveguide and the signal received at the other platen. Phenol-formaldehyde resin was used for preliminary experiments and urea-formaldehyde resin for the main study. The degree of resin curing was assessed by measuring internal bond (IB), which was compared with an AU parameter, root mean square (RMS) voltage. During consolidation, RMS reacted primarily to the change of press pressure; subsequently, it followed the increase in IB and reached a plateau when the resin was completely cured. With extended pressing, RMS decreased, reflecting the degraded condition of the board. These results showed that RMS could be an index for the desired endpoint in pressing.References
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