Study on the Cumulative Damage Behaviors and Microscopic Mechanisms of Epoxy Composite Materials Under a Microsecond Pulse Voltage With a Low Duty Cycle

Abstract

To investigate the degradation processes and the mechanisms of the insulation performance of epoxy composites under pulse voltage, a study was conducted using techniques such as Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) to explore the pulsed breakdown, dynamic mechanical evolution, and surface chemical structural change characteristics. Additionally, molecular dynamics (MD) were employed to investigate the movements of molecules at the microscopic level. The cumulative damage effect and the temperature increase effect of the system during the pulse triggering time led to decreases in the thermodynamic properties of the material, thus decreasing the electrical properties. Under experimental voltages (32–45 kV), the microscale surface morphology, surface chemical state, and thermodynamic performance characteristics of composites were almost unaffected by a single pulse. The composites experienced three stages of cumulative damage: pore/microcrack generation, fusion, and rapid fusion (late insulation life stage). Breakdown occurred extremely quickly after the late insulation life stage. At the microscopic level, the polar functional groups and polar chain segments of the system were influenced by the electric field and elevated temperature. This influence intensified molecular chain motion, thereby accelerating the processes of dissociation of molecular functional groups and rupture of chemical bonds. With an increase in the cumulative pulse count, the rupture of crosslinked network chemical bonds in composites intensified, forming local low-concentration disturbed regions while generating OH groups and other reactive groups, impacting the chemical structure of the material. This change further led to a reduction in the thermodynamic performance, accelerating the degradation of the insulation performance.