Nonlinear shear properties of spruce softwood: experimental results

Shear properties of clear softwood from Norway spruce were investigated by means of the Arcan shear test. The test enabled fairly detailed measurements of pure shear until failure in each of the three orthotropic shear planes, where video extensometry was used for strain measurements. A total number of 85 specimens were tested in 6 different configurations. A varying degree of nonlinearity was observed between the different configurations and material planes, especially for rolling shear. The stress–strain curves were adapted with linear, bilinear and Voce models. Compared to the linearized variant, it was found that the bilinear model generally increases the model accuracy by a factor of approximately two, whereas the Voce model showed even higher accuracy, although its adaptive robustness was somewhat lower. The parameters demonstrated low correlations to density, whereas the correlations with the initial shear moduli in many cases were considerably higher and significant. The correspondence with similar values reported in literature was found to be fairly good.