Measuring Poisson’s ratio: mechanical characterization of spruce wood by means of non-contact optical gauging techniques

In contemporary wood science, computer-aided engineering (CAE) systems are commonly used for designing and engineering of high-value products. In diverse CAE systems, high-fidelity models with a full material description, including elastic constants such as Poisson’s ratios, are needed. Only few studies have dealt so far with the investigation of the Poisson’s ratio of spruce wood (Picea abies (L.) Karst.) or wood in general. Therefore, in the present study all six main Poisson’s ratios of spruce wood were determined in uniaxial tensile experiments by employing optical gauging techniques like electronic speckle pattern interferometry and a combination of laser and video extensometry. Consistent results for the Poisson’s ratios were found by applying these different optical gauging techniques. However, values found in the literature are sometimes considerably different from values established in this study. For that reason, the optical gauging techniques were evaluated with a conventional mechanical extensometer, which proved that there were no significant differences between the established measurements. Finally, in this study the feasibility of different non-contact optical gauging techniques was evaluated and compared through the comparison of the Poisson’s ratios, which showed that non-contact optical gauging techniques are suitable for establishing the Poisson’s ratio of (spruce) wood.