Experiments on the effective compliance in the radial–tangential plane of Norway spruce

Analysis and design of wood based composites and structures need reliable experimental compliance of their constituting materials. Therefore, an experimental method is presented to determine all of the effective in-plane elastic parameters and applied to Norway spruce specimens in the radial tangential RT plane due to the use of this species in wide variety of engineering applications. For the purpose, uni-axial compression experiments are conducted on the specimens for different material orientations under the assumptions of small strains and small rotations. Boundary extremes of the specimens are allowed to rotate for minimizing the boundary artifacts and providing near-ideal specimen deformation. During these experiments, digital image correlation is used to obtain the displacement and strain fields whilst the stress is computed through the applied load and specimen geometry. In addition to the common practice of tabulated parameters for each nominal material orientation, the experiment results are further processed through the transformation rule and least squares function. Consequently, the effective elastic parameters in the RT plane are obtained by taking general anisotropic linear elasticity into account and the material classification is performed. By means of the current method, it is expected to advance the effective in-plane compliance measurements of natural cellular materials.