Analysis of interfacial crack propagation in inhomogeneous bi-materials under thermo-mechanical loading

For the inhomogeneous bi-material structures and typical composites, the propagation behavior of interfacial cracks is significantly affected by discontinuities in material properties and simultaneous action of mechanical loading and temperature. Utilizing the interfacial crack propagation criterion, a numerical calculation framework combining the improved interaction integral and extended finite element method (XFEM) is established to investigate the complex interfacial crack propagation behaviors in thermo-mechanical service environments. The important fracture parameters including stress intensity factors (SIFs) and energy release rate (ERR) at the interfacial crack tip are accurately extracted by using the interaction integral without involving the material derivative. This method enables effective simulation of the propagation path and evolution of interfacial cracks without requiring avoidance of the material interface around the crack tip. By comparing the results with the extension tests of rock-concrete bi-material interfacial cracks in the literature, it is verified that it has high accuracy (error < 2.5 %) in calculating the fracture coefficients at the crack tip and predicting the crack path. For bi-material plates containing interfacial cracks, the conservation of the interaction integral is firstly verified, and then the effects of temperature gradient near the interface, inhomogeneous material properties and crack geometrical configurations on the crack initiation and propagation paths are systematically explored. The numerical results show that the temperature field gradient has a significant effect on mode mixity thereby determining the competing mechanism of whether the crack is delaminated or deflected along the interface. In addition, the effects of the inclusion-to-substrate modulus ratio near the interfacial crack tip and the relative position of the inclusion to the interfacial crack tip on the crack propagation behavior are investigated in a particle composite. Finally, the effect of inclusion on crack propagation is affected by the distance and the stiffness ratio between the inclusion and the matrix, and that this effect has a certain threshold limit.