Simulating fracture in a wood microstructure using a high-resolution dynamic phase field model

As a simplified model, wood can be considered as consisting of hollow cells held together by a weaker middle lamella. We use a high-resolution finite element model, endowed with a phase field model for brittle fracture to model such a structure. The micro-structured discretised materials, with and without middle lamella, differ significantly from a homogenous continuum reference in terms of damage patterns. There is also significant difference between the models with and without middle lamella, since damage localises in the weaker middle lamella, which underlines the importance to include the middle lamella in mechanical analyses. At increased loading velocity, the damage becomes scattered over a larger region ahead of the crack tip, indicating that dynamic effects affect the crack behaviour and that dynamics need to be taken into consideration when loading rates are high or when crack propagation is unstable.