Development of a quick and non-invasive measurement method for the extraction of the dispersion relation in CLT plates for the evaluation of the elastic parameters

This contribution discusses a quick and non-invasive method for the extraction of dispersion relations in CLT panels, with the aim of providing an estimate of the elastic parameters of the plates starting from the fitting of the experimental dispersion curve to the theoretical models. Measurements were performed at the Stora Enso CLT mill on panels that have different thickness and orthotropic ratio. An instrumented hammer was used to excite the plate and accelerometers were used to acquire the impulse responses. Thanks to the reciprocity principle, the measurement points were kept fixed and the hitting point was moved; this allowed to reduce the measurement time and to decrease the number of accelerometers that must be attached. The dispersion curves were evaluated using the phase shift method and the experimental results were fitted with the theoretical models for acoustically thick plates; finally, the elastic parameters were estimated. The results give slightly low estimates of the Young’s modulus and the shear modulus in the stiffer direction, while confirming the datasheet values in the less stiff direction, with deviations depending on the panel thickness. The precision of the hits is also analysed, while a reproducibility study is left for further developments.