ELECTRIC-FIELD-INDUCED INTERFACIAL CRACKING IN MULTILAYER ELECTROSTRICTIVE ACTUATORS

Electric-field induced interfacial cracking in multilayer electrostric tive actuators is studied for two typical cases: (1) an interface crac k lying between an electrode layer and ceramic matrix; and (2) an inte rface crack with one tip at an embedded electrode-edge. Based on the s mall-scale saturation solutions, a direct method is proposed to calcul ate the electric-field induced stress intensity factors that avoids ca lculating the stress field. The effectiveness of the direct method is demonstrated by comparing the results derived with the known numerical solutions. For either case, the explicit condition is given that proh ibits interfacial crack growth by restricting the thickness of ceramic layers and the intensity of the applied electric held. Especially, th e maximum stress intensity factor derived for the above case (2) is fo und to be significantly larger than that obtained in the existing work s for the electrode-tip matrix cracks. This result agrees with the exp erimental fact that interfacial cracking is the dominant failure mecha nism in electrostrictive multilayer devices. Hence, the reliability de sign should be based on the conditions that prohibit interfacial crack ing. (C) 1998 Elsevier Science Ltd. All rights reserved.