Combining nano (GNPs) and micro (CFs) carbon fillers for multifunctional epoxy composites

In this work graphene nanoplatelets (GNPs) and micrometric carbon fibres (CFs) have been added to an epoxy resin for producing high performance composite materials. Rheological analysis indicates that CFs slightly increase viscosity without altering the Newtonian behavior of the epoxy resin, while GNPs significantly increase viscosity due to filler-polymer interactions, shifting the behavior to shear-thinning. The produced composite present improved stiffness and strength, with flexural strength increasing from 77 MPa (neat epoxy) to 120 MPa and the elastic modulus rising from 2.2 GPa to 20 GPa in reinforced samples without changing the glass transition temperature (Tg = 170°C). Adding the fillers, the thermal conductivity increases by 220% and a resistivity of 670 Ω cm is reached in the best performing system. The combination of hybrid fillers enables synergistic reinforcement, making the epoxy composites suitable for advanced structural and thermal management applications.