A new mixed-mode fracture criterion for orthotropic materials, based on strength properties

In this paper, a new methodology for modelling the fracture process zone in cracked wooden structures has been proposed. Implementing this method for modelling the crack tip damage zone could help to establish a new criterion applicable for assessing the fracture of cracked wood specimens under combined mode I/II loading. This criterion involves a damage factor representing the material softening effect due to microcrack existence and growth in the fracture process zone. For calculation of this damage factor, it is not necessary to investigate the complex and non-linear analysis of material behaviour in the damage zone. The approach proposed makes it possible to express an analytical relation for the damage factor as a function of tensile strength along and across the wood fibres. The novelty of this work is that the given method enables not only the arbitrary orientation effects of the original crack with respect to wood fibres but also the T-stress effects in crack growth initiation to be considered. To demonstrate the effectiveness of this method, different case studies have been investigated, and the results obtained by applying the new criterion are compared with available experimental data.