NONDESTRUCTIVE STRENGTH TESTS ON PARTICLEBOARDS WITH ULTRA-SONIC MEASURING TECHNIQUES

The wood properties (high damping, anisotropy) play an important role for the ultra-sonic examinations of wood and wood-based materials. Ultra-sonic examinations of strength and defects are possible for solid wood but complicated due to the difficult coupling of probes to specimen. Informative investigations were carried out on three-layer laboratory particleboards with a modified ultra-sonic test device (type: USIP, manufacturer: Krautkramer) as well as on an appropriate plant for the detection of defects (delamination) (type: UPU, manufacturer: GreCon). There, correlations turned up between the tensile strength and the sound velocity when coupling the probes to specimen in contact. Non-contacting scanning of boards with the fault (delamination) detection plant revealed a certain influence of pressing time and board temperature on the signal amplitude in the ultra-sonic receiver, however, it did not show meaningful correlations with the internal bond strength.