Fracture characteristics of different wood species under mode I loading perpendicular to the grain

Mode I fracture characteristics of different wood species (one softwood and three hardwoods) in two crack propagation systems were investigated using the wedge splitting test under loading perpendicular to the grain. From the obtained load–displacement curves the initial slope, the critical stress intensity factor and the specific fracture energy were determined. The initial slope and the critical stress intensity factor were shown to depend strongly on density within all species whereas for the specific fracture energy differences between the softwood and the hardwoods were found. Differences between the crack propagation systems could be explained by the higher volume fraction of radial oriented tissue (rays) of the hardwoods.