Angular distribution of energy release rates and fracture of piezoelectric solids

Abstract

Applicability of energy release rate criteria to piezoelectric materials is examined in thispaper. The angular distribution of strain and total energy release rates at a crack tip in aplane piezoelectric medium is first formulated by using a branched crack model. Byrelaxing the commonly held assumption of self-similar crack propagation andincorporating in the fracture toughness anisotropy, the criteria of modified strainenergy release rate and modified total energy release rate are applied to discuss thepropagation path of an impermeable crack. Numerical results indicate that thepredictions based on the criterion of modified total energy release rate do not showqualitative agreement with experimental observations, whereas the predictions basedon the criterion of modified strain energy release rate appear more promising.Based on the criterion of modified strain energy release rate, a crack tends tobranch off from a straight path under a positive electric loading, regardless ofcrack orientation. An applied electric field can either promote or retard crackpropagation depending on the direction of electric field, crack orientation andcrack extension direction. The predictions made by the energy-based criteria arecompared with those corresponding to a recently reported stress-based criterion.