LAUSR

Abstract The double notched shear test specimen has been redesigned to test wood in structural component scale using a compression test setup. A parametric finite element method (FEM) study was performed to obtain the best specimen shape within a domain of geometrically feasible layouts. Several criteria of stress state assessment were considered to characterize the shear zone. Experiments employing DIC (Digital Image Correlation) were performed on the optimized specimens both for RL (Radial-Longitudinal) and TL (Tangential-Longitudinal) material orientation of shear fracture surfaces for the wood of Norway spruce. Two series of specimens with different notch end shapes were tested. Fracture surfaces were 3D laser scanned post-failure, and the actual areas were determined. Shear moduli, nominal and real shear strengths, as well as fracture surface orientations, were evaluated. The deformation fields were fitted to the analytical fracture mechanics solutions to identify the intensity of the opening and shearing modes at the notch. The resulting shear strengths were compared with the existing clear wood specimen test results of Norway spruce using fracture surface composition obtained from 3D scan analyses. For both specimen designs, the estimated shear moduli are on the same level G=1020 MPa. The shear strengths differ considerably, which is correlated positively to the intensity of the opening deformation mode at the notch. The analysis of fracture surface scans reveals the superposition of shear strengths in RL and TL.