Failure mechanisms of clear wood identified at wood cell level by an approach based on the extended finite element method

Within wooden boards, initiation and global direction of cracks are governed by structural features on the microscale. Thus, and to account for the layered structure of wood, all possible failure mechanisms for two repetitive units are identified by an approach based on XFEM. The resulting failure modes of 800 numerical fracture simulations for each cell type are classified and lead to the definition of two multisurface failure criteria. Finally, these criteria are applied to tensile tests at the annual year ring scale, showing that the developed approach is able to reproduce essential failure mechanisms in wood correctly.