Electrical Percolation in Hybrid Carbon‐Filled Glass Fiber–Epoxy Composites: Microstructural and Spectroscopic Correlation

ABSTRACT

Electrical percolation in polymer composites loaded with carbon nanofillers depends on the dispersion, distribution, and interconnections of conductive fillers. But the results of dispersion studies and electrical data are seldom interpreted in relation to each other. The present study establishes a connection between electron microscopy, X‐ray diffraction, optical and IR spectroscopic analysis and electrical characteristics of glass‐fiber/epoxy nanocomposites: an unmodified reference (EG), an aluminium‐trihydrate‐modified system (EGA), a hybrid carbon‐nanotube/nanoplatelets system (EGH), and a combined hybrid‐filler‐plus‐trihydrate system (EGAH). Scanning electron microscopy provides images of fine non‐agglomerated filler dispersion with strong fiber‐matrix adhesion in hybrid nanocomposites. X‐ray diffraction reveals the loss of sharp reflection peaks for nanotubes and nanoplatelets in hybrid systems EGH and EGAH, attenuation of the MWCNT and GNP reflections, consistent with fine dispersion. Optical spectroscopic analysis proves that the value of the band gap decreases from 3.05–3.10 eV to 2.68–2.95 eV while the IR spectrum confirms the unchanged structure of the matrix. AC electrical conductivity (from 10 Hz to 2 MHz) reveals a frequency independent plateau (1.6–1.8 × 10 ⁻² and 2.7–5.9 × 10 ⁻³  S/m) in EGH and EGAH, which is 4–5 orders of magnitude higher than in EG and EGA (10 ⁻⁷ –10 ⁻⁵ S/m) accompanied by a higher low‐frequency dielectric permittivity enhancement characteristic of a percolated network. Characteristic results observed provide consistent description for the transition from dielectric to electrically conductive behavior in the hybrid MWCNT/GNP‐filled glass‐fiber/epoxy composites.