Modeling Breakdown-resistant Composite Dielectrics

Using the analogy between dielectric breakdown and mechanical fracture, a phase-field model for dielectric damage initiation and evolution has been developed. The model utilizes a continuous field of damage variable to differentiate a localized conductive channel and the undamaged bulk material. By employing a Griffith type energy criterion for the propagation of a conductive channel, direct handling of the intricate microscopic details in the process zone is avoided. This paper implements the model into a finite-element code, and studies the breakdown-resistant effect of various types of composite structures. Numerical calculations suggest that fillers of higher permittivity and elliptic shapes or in laminate structures are more effective in resting conductive channels and resisting catastrophic breakdown. Weak sacrificial fillers, which cause the composite to undergo a two-stage damage process, are also found very effective in breakdown resistance.