NONDESTRUCTIVE MEASURING OF MODULUS OF EL ASTICITY AND MODULUS OF SHEAR OF PARTICLE BOARDS USING BENDING VIBRATIONS

With one- and threelayered laboratory particle boards and industrial p article boards investigations were undertaken to measure modulus of el asticity and modulus of shear by bending vibrations. Modulus of elasti city can be calculated from natural frequencies of boards clamped at o ne side (cantilever). Correlations between modulus of elasticity and m odulus of rupture were also determined. Modulus of elasticity increase s with cantileverlength partly due to influences of shear. A formula w as developed to describe modulus of elasticity as function of cantilev er length depending on two parameters which must be determined experim entally - one is related to the modulus of elasticity at infinite cant ileverlength and the other correlates with the modulus of shear which applies for the bending.