Polymer-based dielectrics with high energy storage density
are
attracting increasing attention due to their wide applications in
pulsed-discharge and power conditioning electronic fields. Despite
some numerical simulation about effects of horizontally arranged and
vertically arranged fibers on dielectric properties of composites
already studied, the influence mechanism of the specific orientation
and aspect ratio still remains to be studied. In this work, the effects
of orientation angles and aspect ratios of nanofiber fillers on breakdown
behavior and dielectric properties of composites are theoretically
analyzed by the finite element and phase-field method. The results
show that the more inclined the nanofiber fillers is, the higher the
nominal breakdown strength is, which benefits from the obstruction
of the conductive channels by the nanofibers. However, the dielectric
constant shows the opposite law, which is the result of the decreased
polarization along the electric field direction of the nanofiber fillers.
Besides this, by modulating the distribution of local electric field,
a higher aspect ratio of nanofiber fillers helps to achieve a much
higher breakdown strength with a slight sacrifice of dielectric constant.
The present work provides a comprehensive and quantitative understanding
of the orientation and aspect ratio of nanofiber fillers on the dielectric
and breakdown properties of composites, providing important guidance
on optimizing the energy storage performance.
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