Assessing the Effect of Swelling Pressures in Particleboard and MDF Using Acoustic Emission Technology

Robert W. Rice, Chunyan Wang

Abstract


The interaction of moisture with wood-based composites leads to the development of swelling pressures that cause the failure of resin bonds and the dislocation of fibers within the composites. These bond failures and dislocations can result in abrupt stress changes that trigger vibrations and create acoustic emissions (AE). Resin and wax levels within the composites effectively limit the interaction of wood and water and affect the level of AE. In this research, acoustic emissions were used to measure the effects of resin and wax levels in both particleboard and medium density fiber-board (MDF).

Two resin levels and three wax levels in the composites were tested. Samples were immersed in distilled water for 120 min during which cumulative AE were recorded. In addition, the density and moisture content gains of the samples were determined.

The results provide evidence that both resin and wax levels significantly affect the number of acoustic emissions and the failure of internal bonds within the samples. Increasing the percentage of wax reduced the level of acoustic emissions in both the MDF and particleboard. Increasing the percentage of resin significantly affected the levels of AE in both MDF and particleboard, although in different ways because of the differences in internal structure within the composites. Acoustic emission technology could be a useful tool in assessing the quality and consistency of the composites.


Keywords


Acoustic emissions;nondestructive testing;wax;particleboard;resin;medium density fiberboard

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