Mixed mode fracture criterion for wood based on a reinforcement microcrack damage model

Taking into account the effect of fracture process zone, an efficient mixed mode I/II fracture criterion for arbitrarily oriented cracks in orthotropic materials like wood is presented. New approach, referred to here as “reinforcement microcrack system” is proposed for accurate modeling of the crack tip local damage zone. This method incorporates reinforcement effect of the fibers into progressive loss of stiffness due to the growth of microcracks in damage zone. Material parameters of this model are functions of undamaged primary elastic properties of wood, and can be extracted easily. Comparison with available experimental data shows the capabilities of the presented criterion.

Research highlights▶ A new criterion for mixed mode fracture analysis of wood specimens with arbitrarily oriented macro-crack with respect to the orthotropy axes is presented. ▶ An analytical expression for accurate modeling of the fracture process zone in wood is presented (So far, an analytical expression for the calculation of effects of fracture process zone, had to the author's knowledge not been proposed). ▶ This criterion makes a transition of nonlinear fracture mechanics into practical considerations of engineering wooden components. ▶ The new criterion improves the reliability of the resulting fracture limit curves as it closely estimates the available experimental data.