Fracture mechanics of piezoelectric materials – Where are we right now?

Piezoelectric and ferroelectric materials have gained extensive applications in electromechanical devices, microelectromechanical systems and smart composite materials. In order to assess the strength and durability of those materials and components, exhaustive theoretical and experimental investigations have been performed over the past three decades. The aim of the paper is to give a short overview and a critical discussion about the present state in the field of piezoelectric fracture mechanics. After an introduction, linear piezoelectric fracture theory is explained with emphasis to special features like anisotropy, mode mixture and electric properties of cracks. Next, suggested fracture criteria are presented and contrasted with experimental observations in fracture testing. Cracks under static, cyclic and dynamic loading by electrical and mechanical fields are taken into account. A great challenge is to tackle the non-linear phenomena and ferroelectric domain switching in the fracture process zone. Finally, conclusions are drawn with respect to open problems and desirable future research areas. To limit the scope of the paper, fracture behavior of interface cracks will not be addressed.