Quasi-static and dynamic fracture behavior of lead zirconate titanate: A study of poling and loading rate

Abstract

In this study, coupon specimens of both poled and de-poled lead zirconate titanate (PZT) are examined under quasi-static and stress-wave loading conditions. Mode-I crack initiation and fracture behavior is examined using ultra high-speed imaging in conjunction with 2D digital image correlation on symmetrically impacted specimens. Measured displacement fields ahead of the dynamically loaded crack tip are used to extract the critical stress intensity factor (KICd) at initiation and are compared with quasi-static SENT fracture toughness tests. Results demonstrate that under static conditions, the difference between poled and de-poled specimens is not statistically significant, however under dynamic conditions, poled samples exhibited a 70% greater fracture toughness compared to the de-poled specimens. To verify the increase was not due to thermal degradation of material mechanical properties during the de-poling process, re-poled specimens were also prepared and examined under dynamic fracture loading conditions. In general, impulsively loaded samples exhibited greater fracture toughness compared to their quasi-statically loaded counterparts, regardless of the poling. Specifically, the critical stress intensity factor increased seven to tenfold compared to static fracture toughness values, with poled samples exhibiting the greatest toughness of all samples explored. In terms of rate, the increase in fracture toughness under dynamic conditions likely comes from microcracking and potentially phase transformations at the crack tip. In terms of poling, the increase in fracture toughness is likely due to a bulk manifestation of ferroelastic toughening, where dynamic domain reorientation provides crack tip shielding.