Determination of the internal bond of particle board and fibreboard.

Tensile strength perpendicular to the surface is generally used as a measure of the internal bond of particleboard and fibreboard. This strength property cannot be used in structural strength calculations. Besides, determining the tensile strength perpendicular to the surface is troublesome. The object of this research was to find correlations between the tensile strength perpendicular to the surface and other strength properties and to detect a more easily determinable strength property for describing the internal bond of boards. The test material comprised 124 particleboards and 95 fibreboards from the standard production of Finnish factories. The following board properties were determined: density, moisture content during the tests, tensile strength perpendicular to the surface, shear strength, tension-shear strength, torsion-shear strength, torsion strength, and modulus of rigidity. The results show that torsion strength and torsion-shear strength correlate most strongly with the tensile strength perpendicular to the surface. Further investigations must thus be concentrated on developing a suitable method of determination for these strength properties.