Predictions of fracture resistance of spruce wood under mixed mode loading using non-local fracture theory and numerical modelling

A novel analytical model to predict fracture resistance of a quasi-brittle material, like wood, is presented. The model is based on a scaling parameter introduced into the non-local fracture theory to take into account the specimen size effect on the development of the damage zone. An expression for length of the critical process zone, which can be used in damage tolerant design of wooden structures is derived from this theory. The model is validated with mixed-mode bending tests. A numerical analysis using cohesive elements is performed to understand the role of specimen size in the development of the damage zone. The analytical predictions of the fracture resistance and the critical process zone length for wood are compared with numerical results and experimental data available in the literature.