Numerical analysis of the MMB test for mixed-mode I/II wood fracture

In the present work, a numerical study of the MMB test was performed. The main objective is to verify its adequacy to fracture characterization of clear wood from maritime pine (Pinus pinaster Ait.), under mixed-mode loading in the RL crack propagation system. A three-dimensional finite element analysis, including a cohesive damage model, was performed. It was verified that calculation of the apparatus lever length using corrected beam theory improves the required mode mixity. The results of the numerical simulations (applied load and displacement) were used as input data in a new data reduction scheme based on specimen compliance. The method includes an equivalent crack concept related to the fracture process zone and provides accurate values of mode I and II strain energy release rates, GI and GII. Furthermore, it does not require crack measurements during propagation.