Effect of graphene filler on the mechanical, electrical, and thermal properties of polymer composite

Abstract

Carbon fiber reinforced polymer materials (CFRP) form vital components in many types of vehicles such as airplanes, spacecraft, submarines, and transport vehicles. They achieve comparable mechanical properties to ordinary metals, but with a lower density. This allows vehicles to become lighter which reduces fuel consumption, air pollution, and related costs. Researchers have demonstrated that the failure of the composite part is often induced by a defect at the fiber/matrix interface. The matrix bond quality is a critical factor that dictates the overall structural properties. Thus, enhancing the matrix of a polymer composite presents an avenue to improve the mechanical properties of CFRP materials. CFRP materials are carbon fiber-based composites. The electrical and thermal conductivities of carbon fiber are extremely high. However, polymetric matrices are insulative materials that dramatically reduce the electrical and thermal conductivities of the overall CFRP composite. The thermal conductivity is a pivotal factor in the machinability of CFRPs. Higher conductivity dissipates the heat from the workpiece/cutting tool. This reduces the cutting temperature and extends the service life of the cutting tool. In this study, we aim to improve the CFRP mechanical properties and the thermal/electrical conductivities of the epoxy matrix through the incorporation of graphene particles into the matrix. In the first part of this work, the electrical properties of composites with five different graphene concentrations (0, 3, 5, 7, and 10 wt. %) were evaluated through the broadband dielectric spectroscopy (BDS). The results demonstrate a four-fold enhancement at 10 wt. % of graphene filler and the percolation threshold was achieved with only 7 wt. %. The thermal conductivity was assessed qualitatively through the differential scanning calorimetry (DSC). Samples with 10 wt. % of graphene showed around 16 % reduction in their specific heat capacity which can be translated into an enhancement of the thermal conductivity. In terms of mechanical properties, a suitable manufacturing method of the CFRP was developed. This approach leads to a consistent fiber volume fraction with a minimum void level and a good graphene dispersion. With this process, the impact of the graphene on the mechanical properties of the CFRP can be accurately assessed. Seven graphene concentrations ranging from 0 wt. % to 3 wt. % were tested. Samples with 0.25 wt. % showed the best flexural strength and interlaminar shear strength with an improvement of 5%.

Date	7 Dec 2020
Original language	American English
Awarding Institution	École de technologie supérieure
Supervisor	Jean-François Chatelain (Supervisor) & Gilbert Lebrun (Co-supervisor)