Phase field simulations on domain switching-induced toughening or weakening in multiferroic composites

The unique electro-magneto-elastic coupling effect in multiferroic materials provides a potential application in actuators, sensors and memory devices. Upon applying mechanical loads, a concentrated stress may appear near the voids or cracks in multiferroic materials, which could induce the switching of polarizations and magnetizations (also called domain-switching). In this work, a phase field model is employed to investigate the domain switching-induced toughening or weakening in ferromagnetic/ferroelectric composites subjected to mechanical loads. It is found that the influence of domain-switching on the stress intensity factors (SIFs) is dependent on the crack positions and the forms of mechanical load. When a stress load is applied to the specimen with an edge crack, the SIFs increase and result in weakening in the multiferroics. However, for the specimens with a central crack or with a displacement load, the SIFs are decreased by domain-switching, resulting in toughening in the multiferroics. The present study provides a microstructural explanation on the complicated nonlinear fracture behaviors of multiferroic composite materials.