Dielectric breakdown behavior of unidirectional carbon fiber reinforced composites with different fiber volume fractions

The dielectric breakdown damage of carbon fiber reinforced polymers is an important factor affecting its structural safety during application in the high electric field. This paper investigates the dielectric breakdown behavior of unidirectional carbon fiber reinforced composites with different fiber volume fractions and yarn distributions. Comparing the experimental testing, finite element analysis, and equivalent analytical model, the dielectric breakdown behaviors are elucidated. The results reveal that dielectric breakdown voltage decreased by more than 50% as the carbon fibers distributed to the surface densely. The electric field became more concentrated after the surface resin breakdown, which would weaken the breakdown strength of the composite. Increasing fiber volume fraction from 7.2% to 56.6% leads to an order of magnitude decrease in the dielectric breakdown voltage (from 3.07 to 0.35 kV). The dielectric breakdown voltage shows a nonlinear decreasing with the increasing fiber volume fraction, which is governed by the spatial evolution of localized electric field enhancements induced by carbon fibers. This study is meaningful for the dielectric properties design of carbon fiber composites under high electric fields.