On the inverse identification of wood elastic properties using a DIC-based FEMU approach

This work aims to identify the linear elastic orthotropic material parameters of Pinus pinaster Ait. wood using full-field measurements and an inverse identification strategy based on the finite element method updating (FEMU) technique. Compression tests are carried out under uniaxial and quasi-static loading conditions on wood specimens oriented on the radial-tangential plane, with different fibre orientations: (i) on-axis and (ii) off-axis specimens with a grain orientation of 60º to the loading direction. Full-field displacements and strains are measured using digital image correlation (DIC), which are then used as a reference in the identification procedure. 
A finite element model is developed assuming plane stress conditions, where wood is modelled as an orthotropic homogeneous material. Based on the numerical results, a synthetic deformed image is created and processed by DIC and further compared to the experimental results. This approach ensures a fair comparison between both sets of data since the full-field strain maps are obtained through the same filter and therefore have the same strain formulation, spatial resolution and data filtering. Firstly, the identification is performed using a single configuration, either the on-axis or the off-axis specimen. Secondly, the identification is carried out by merging data from both on-axis and off-axis configurations. Moreover, the results obtained from this DIC-based FEMU inverse identification methodology are compared to the ones from the classical FEMU approach. The results from both approaches were similar when using multiple configurations. However, when using the DIC-based FEMU approach with the on-axis configuration, the identified modulus of elasticity in the tangential direction and shear modulus are closer to the reference values, demonstrating its superiority.