Toughening and weakening in ferroelectric ceramics by domain-switching process under mixed electric and mechanical loading

Abstract

The structural reliability of ferroelectric ceramics calls for a better understanding of the mechanism of fracture. For a ferroelectric ceramic under mechanical and electric loadings, the intensified stress and electric fields in the vicinity of a crack tip lead to polarization switching. The switched zone induces an incompatible strain and, consequently, changes the stress intensities and the apparent fracture toughness. This article investigates the effects on fracture parameters of an initially poled ferroelectric ceramic induced by polarization switching in the case of small-scale switching. The changes of stress intensities and energy release rate at the crack tip induced by the switched zone are calculated when the specimen is under both electric and mechanical loadings. Our results show that a switched zone usually produces both mode I and mode II stress intensities at the crack tip, and the increments are strongly dependent on the initial poling direction and electric-field strength. With certain initial poling directions, the material could be toughened, whereas, with other directions, be weakened. Generally, high-magnitude electric fields (both positive and negative) decrease the material toughness when both the mechanical and electric fields at the crack tip are singular.