A numerical approach to describe failure of wood - From the wood cell level up to wood-based products

Abstract

For the description of the failure processes in clear-wood, a multiscale approach, based on the Finite Element (FE) method, was performed. In a previous work, failure mechanisms at the single wood cell level were identified by using a unit cell approach in combination with the eXtended Finite Element Method (XFEM). Finally, a multisurface failure criterion was obtained. Within this work, these results were combined in another unit cell at the annual year ring level, where late-(LW) and earlywood (EW) cells form a layered structure. Subsequently, a single multisurface failure criterion with predefined global crack directions at the clear-wood level could be won, which will be implemented into the commercial FE software Abaqus through a subroutine. In combination with a previously developed FE simulation tool, which allows the 3D virtual reconstruction of different wood-based products, including knots and the surrounding fiber deviations, the main failure mechanisms in such products can now be captured realistically. Thus, the influences of knot configurations on several effective properties, like modulus of elasticity or bending strength, can be determined. Moreover, the resulting effective stiffness properties are used to study strengthening and load-transfer effects between lamellae in Glulam and CLT elements.