Ultra-lightweight foam core particleboards have been produced in a novel one-step process with resinated wood particles for the faces and expandable polystyrene (EPS) as core layer material. The mechanical and physical properties of panels were investigated in terms of the different foam core densities and press parameters (temperature, pressing and foaming time). The bending strength properties of the panels were not signifi cantly changed with increasing foam core density from 80 to 120 kg m -3 . Panels produced at a press temperature of 130 ° C (1-EPS) have an improved core-face interface and also a denser surface layer, which positively infl uences the internal bond and thickness swelling. The panels produced at a press temperature of 160 ° C (2-EPS) have smaller and more foam cells and an improved fusion of foam beads and properties, which have a positive infl uence on the edge screw withdrawal resistance and water absorption.
Air-coupled ultrasonic inspection for the detection of delaminations inside panels is a widely applied technique in the wood-based panel industry. Additionally, the ultrasonic signal is used to monitor the constancy of the production process as unsteady material properties and process parameters cause variations in the transmitted ultrasonic signal. This article examines the physical effects of aircoupled ultrasonic testing and analyses the influences of panel density and particle type on the transmitted ultrasonic signal. The experiments were carried out for a broad range of wood-based panels. The experimental results indicate that the tested properties influence the transmission in two ways. Firstly, density affects the reflection and transmission factors at the material boundaries, and secondly, particles and pores act as scattering centres inside the material, leading to an attenuation of the ultrasonic signal. The results of this study may be used to efficiently include the ultrasonic signal into a trending system for the wood-based panel production process.
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