No abstract

A new testing method measuring the specific fracture energy of wood-based panels in Mode I is proposed. Three types of wood-based panels, i.e. oriented strand board (OSB), particleboard (PB) and medium density fibreboard (MDF) are investigated, using fracture energy and the industrial European standard method of internal bond strength according to EN 319. Double cantilever beam specimens are notched in the middle layer to introduce an initial crack. To apply tensile load perpendicular to the surface of the panels to open the crack in Mode I specimens were adhesively bonded to steel braces. Besides the calculation of the total fracture energy an advanced analysis of the loadÁdisplacement curve was also performed. Results of the fracture energy method were compared to internal bond strength (IB). Specimen shape is optimized for industrial purposes using double cantilever beams, while the determination of the fracture energy is performed by simple integration of the loadÁdisplacement curve. While IB showed a large scattering of data, the fracture energy test yielded statistically significant differences between the board types.

Particle boards were produced from different types of wood particles, i.e. spruce, recovered particles, willow, poplar, and locust. Effects of raw material, as well as varying resin content on mechanical and fracture mechanical properties were investigated. For the analysis of mechanical properties, specific fracture energy, stress intensity factors, and the industrial European standard methods internal bond strength according to EN 319 and bending strength according to EN 310 were used. The total fracture energy was measured, and the stress intensity factor was calculated by means of data achieved through finite element simulations. Results of the fracture energy analysis were compared to internal bond strength (IB) and bending strength. While IB and the modulus of elasticity (MOE) showed a high variability, data scattering for fracture energy tests and modulus of rupture (MOR) were smaller, which are due to significant differences between the resin contents of the various board types.