Dielectric, low-frequency noise and mechanical properties of hybrid carbon nanotubes/graphene nanoplatelets epoxy composites

This study analyzes the electrical, microwave (26-37 GHz), low-frequency (20 Hz-10 kHz) noise, and mechanical properties of epoxy hybrid composites filled with multi-walled carbon nanotubes (MWCNT) and graphene nanoplatelets (GNP). The system's percolation threshold was around 0.25 vol.% MWCNT, while the electromagnetic properties were almost independent of GNP concentration. The composites are shown to be suitable for electromagnetic shielding in the 26-37 GHz range, with microwave absorption increasing as the total nanocarbon concentration rises. The electrical transport in these composites is governed by one-dimensional Mott hopping at low temperatures (below 245 K) and redistribution effects above room temperature. The low-frequency voltage noise spectra of the composites are predominant of the 1/f component, with noise spectral density proportional to Ub, where the exponent b is close to 2, indicating noise caused by resistance fluctuations. The optimal electromagnetic properties are near 0.5 vol.% MWCNT and 0.25 vol.% GNP concentrations. The tensile elastic modulus and yield strength showed the highest increases at 0.25/0.25 loading, with gains of 40.43% and 16.77%, respectively, compared to neat epoxy. Fracture toughness and energy release rate increased with adding 0.25 vol.% GNP, while Charpy impact strength improved with higher MWCNT loading.Highlights Percolation threshold in hybrid MWCNT/GNP composites is close to 0.25 vol.% MWCNT Low-frequency voltage noise spectra of the composites are 1/f type Frequency dependence of the dielectric permittivity and electrical conductivity in the 20 Hz-1 MHz frequency range. image