NONDESTRUCTIVE STRENGTH TESTS ON PARTICLE BOARDS 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. Ult ra-sonic examinations of strength and defects are possible for solid w ood but complicated due to the difficult coupling of probes to specime n. Informative investigations were carried out on three-layer laborato ry 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 s ound velocity when coupling the probes to specimen in contact. Non-con tacting scanning of boards with the fault (delamination) detection pla nt 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.