Analytical model for the transient permittivity of uncured TiO 2 whisker/liquid silicone rubber composites under an AC electric field

Abstract The electric field grading of dielectric permittivity gradient devices is an effective way of enhancing their insulation properties. The in situ electric field‐driven assembly is an advanced method for the fabrication of insulation devices with adaptive permittivity gradients; however, there is no theoretical guidance for design. In this study, an analytical model with a time constant is developed to determine the transient permittivity of uncured composites under an applied AC electric field. This model is based on optical image and dielectric permittivity monitoring, which avoids the direct processing of complex electrodynamics. For a composite with given components, the increased filler content and electric field strength can accelerate the transient process. Compared with the finite element method based on differential equations, this statistical model is simple but efficient, and can be applied to any low‐viscosity uncured composites, which may contain multiple fillers. More importantly, when a voltage is applied to an uncured composite insulating device, the proposed model can be used to analyse the spatiotemporal permittivity characteristics of this device and optimise its permittivity gradient for electric field grading.