Wedge splitting test of wood for fracture parameters estimation of Norway Spruce

Crack evolution in wood from Norway Spruce during mode I wedge splitting tests was measured using a Digital Image Correlation (DIC) system. The resulting series of deformation fields were post-processed in order to obtain kinematically based crack tip location histories throughout the loading procedure, by a purposely made algorithm. The developed algorithm is based on generic mode patterns which are fitted to the observed deformation fields and optimized. The developed procedure and its application are explained and the resulting crack paths are presented. Subsequently, fracture energies, critical stress intensity factors and experimental resistance curves were derived based on the crack path data. Comparisons of the obtained material parameters for fracture mechanics with literature values show that the proposed method is a powerful alternative to the more traditional methods. Moreover, experimentally derived crack tip location histories give more detailed insight into the behaviour of wood (Norway Spruce) during mode I fracture and may replace indirect methods and crack length assumptions.