Experimental investigation of mesoscale variability of clear spruce mechanical properties in the radial direction

The aim of this work is the investigation of mesoscale/local variability in mechanical properties of clear timber in the radial direction. Clear Norway spruce wood, Picea abies, was used for cutting specimens of different lengths with a small cross-sectional area of 4 × 4 mm2, in the radial direction of timber boards, and tested under tensile loading. In some boards, specimens were positioned regularly and, in some others, randomly, and local deformations in each specimen were measured during the tests. The results indicate a significant variability in the specimens’ elastic moduli and strengths. A correlation between the mesostructure of clear timber and mesoscale/local variability of the transverse elastic modulus in the specimens was observed. Specimens’ failures were classified and a reasonable correlation with the corresponding strength values was observed.