Evaluation of the strain-based partitioning method for mixed-mode I+II fracture of bi-material cracks

The goal of this paper is to evaluate the strain-based partitioning method (SBM), an analytical method based on beam analysis, for the mixed-mode fracture characterization of asymmetric cracks. The fracture energy is calculated at the crack tip of mixed-mode bending (MMB) test with asymmetric geometry and asymmetric material parameters. The fracture energy obtained using SBM is benchmarked against the widely applied Williams’ partitioning method (WM) and numerical results from finite element models using the virtual crack closure technique (VCCT). Results show that WM produces inaccurate fracture modes in asymmetric conditions. However, if using SBM, the fracture mode ratio of bimaterial cracks was obtained with accuracy. SBM describes a coupling function between mode I and mode II fracture that allows the mode partitioning as long the specimen complies with a simple design criterion based on the longitudinal strain equivalence between arms. Experimental results of composite-to-metal bonded joints validate the results of the parametric study. SBM proves to be an easy and reliable solution for the mixed-mode fracture characterization of bi-material cracks.