The effect of electrostatic tractions on the fracture behavior of a dielectric material under mechanical and/or electric loading is analyzed first by studying a pre-cracked parallel-plate capacitor and illustrated by plots. The research is then extended into the case of piezoelectric materials considering the anisotropic material properties and the piezoelectric effect. The results are illustrated by plots based on a specific lead zirconate titanate (PZT-5H) sample, and also for another piezoelectric material with even higher dielectric/piezoelectric constants.

The results are presented in terms of electrostatic tractions, crack opening/closing, and energy release rate. For dielectric materials, electrostatic tractions on the electrodes compress the material in front of the cra...[ Read more ]

The effect of electrostatic tractions on the fracture behavior of a dielectric material under mechanical and/or electric loading is analyzed first by studying a pre-cracked parallel-plate capacitor and illustrated by plots. The research is then extended into the case of piezoelectric materials considering the anisotropic material properties and the piezoelectric effect. The results are illustrated by plots based on a specific lead zirconate titanate (PZT-5H) sample, and also for another piezoelectric material with even higher dielectric/piezoelectric constants.

The results are presented in terms of electrostatic tractions, crack opening/closing, and energy release rate. For dielectric materials, electrostatic tractions on the electrodes compress the material in front of the crack tip and stretch the material behind the crack tip, having the tendency to close the crack. Mechanical load is the driving force to propagate the crack, while applied electric field retards crack propagation due to the electrostatic tractions. As a direct consequence, the fracture criterion is composed of two parts: the energy release rate must exceed a critical value and the mechanical load must be higher than the critical value for crack opening.

The investigation into piezoelectric materials indicates that influence of electrostatic tractions depends on the direction of applied electric field due to the piezoelectric effect. Under a positive electric field (aligned with the poling direction), the electrostatic tractions stretch the material behind the crack tip and have the tendency to close the crack. While under a negative electric field (opposite to the poling direction), the electrostatic tractions compress the material behind the crack tip and promotes crack opening process. Mechanical load is always the driving force to propagate the crack, while the effect of electric loading on the crack propagation due to the electrostatic tractions depends on applied electric field direction. The fracture criterion is composed of two parts: the energy release rate must exceed a critical value and the mechanical load must be higher than the critical value for crack opening. Special attention has to be paid to the loading condition under negative electric field due to its contribution to assisting in the crack opening process.