A trade-off between enhancement of physical properties of the final part and the processability during manufacturing always exists for the application of nanocarbon materials in thermoset-based composites. For different epoxy resins, this study elaborates the impact of nanocarbon particle type, functionalization, and filler loading on the resulting properties, i.e., rheological, electrical, thermo-mechanical, as well as the fracture toughness in mode I and mode II loading. Therefore, a comprehensive set of carbon nanoparticles, consisting of carbon black (CB), single-walled carbon nanotubes (SWCNT), multi-walled carbon nanotubes (MWCNT), few layer graphene (FLG), and electrochemically expanded graphite (ExG), in purified or functionalized configuration was introduced in various epoxy resins, with different molecular weight distributions. A novel technique to introduce sharp cracks into single-edge notched bending (SENB) fracture toughness specimens led to true values. SWCNT show highest potential for increasing electrical properties without an increase in viscosity. Functionalized MWCNT and planar particles significantly increase the fracture toughness in mode I by a factor of two.
Keywords: fracture toughness; mode I; mode II; nano composites; percolation; viscosity.