Modelling inter- and transgranular fracture in piezoelectric polycrystals

A cohesive zone finite element model for quasi-static fracture of piezoelectric polycrystals is proposed. Interface elements are used to model both inter- and transgranular fracture. Electromechanical constitutive relations are derived by enhancing commonly used mechanical traction-opening laws with relations for a parallel plate capacitor. Numerical simulations demonstrate that the proposed model correctly mimics several experimentally observed phenomena. Most importantly the switch from mainly intergranular to mainly transgranular fracture with increasing grain size is modelled correctly. The model also correctly mimics the influence of an electric field on the ultimate load.