Dielectric breakdown behaviors and high-voltage damages of 3D braided carbon fiber/epoxy resin composites

Dielectric breakdown of carbon fiber reinforced polymers is a key factor affecting the lightning protection design of engineering applications. This paper presented a coupled phase field-electrical-thermal model to reveal dielectric breakdown evolution and damage morphology of three-dimensional (3D) braided carbon fiber/epoxy composites. Finite element analysis (FEA) results show that dielectric breakdown occurs in the shortest conductive path along the electrical field direction. The braided yarns outside the shortest path also exhibit a breakdown tendency, which weakens the dielectric breakdown voltage. Testing results verify that dielectric breakdown voltage decreases from 3250 V to 337.5 V as the increasing carbon fiber yarns. Increasing the equivalent length of braided yarn along the loading direction decreases the dielectric breakdown voltage. Furthermore, a similar elliptical damage is observed at the surface braided knot from both the FEA model and the testing results. The verified model finds that both electric potential and current density distributions within the composite undergo abrupt transitions upon complete dielectric breakdown, which further reveals the dielectric breakdown progress.