Abstract
This is the second part of an article series where the mechanical and fracture mechanical properties of medium density fiberboard (MDF) were studied. While the first part of the series focused on internal bond strength and density profiles, this article discusses the fracture mechanical properties of the core layer. Fracture properties were studied with a wedge splitting setup. The critical stress intensity factors as well as the specific fracture energies were determined. Critical stress intensity factors were calculated from maximum splitting force and two-dimensional isotropic finite elements simulations of the specimen geometry. Size and shape of micro crack zone were measured with electronic laser speckle interferometry. The process zone length was approx. 5 mm. The specific fracture energy was determined to be 45.2 ± 14.4 J/m2 and the critical stress intensity factor was 0.11 ± 0.02 MPa.
Highlights
Wood based panels consist of wood particles, fibres, flakes or veneer sheets which are usually processed with a resin and treated with pressure and heat
This paper presents electronic speckle pattern interferometry (ESPI) measurements in order to determine the crack length and to verify the FE modelling
Specimens for testing the middle layer of medium density fiberboard (MDF). They provided experimental results for the initiation toughness Gc and the modulus of elasticity E from simulations of 19 mm thick MDF boards. To compare their results with the results presented here, the well-known equation from linear elastic fracture mechanics was used: K Ic G Ic
Summary
Wood based panels consist of wood particles, fibres, flakes or veneer sheets which are usually processed with a resin and treated with pressure and heat. The different performance of wood based panels mainly depends on the exclusion of naturally grown strength failure zones, such as for instance knots or any other type of fibre deviation The design of such new products requires a high yield of information and a precise quality control system. For the analysis of the core layer of MDF, loading must be carried out perpendicularly to the plane of the board This required some modifications to the traditional wedge splitting configuration used by Tschegg [3], where the recess for the load transmission pieces is cut into the specimen. The results gained are used to analyse the appropriateness of the calculated models and to determine the applicability of the adopted wedge splitting experiment for the analysis of the core layer in wood based panels
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