The influence of a carbon nanoparticle modification on the damage behaviour and resulting mechanical properties of an epoxy matrix is experimentally investigated. A comparison of different nanoparticle morphologies with regard to their potential use in FRP is carried out. Since the volumes between the fibres in FRP are very small, the focus is set on the investigation of size effects of polymer nanocomposites. The influence of local microdamage at the particles on the mechanical properties in a small volume is discussed by comparing the different energy dissipating damage mechanisms in dependence of the nanoparticle morphology. Crack initiation and damage mechanisms at the different nanoparticles can be clearly identified. For layered particles such as few layer graphene, it is found that the orientation of the graphene layers with regard to loading direction is critical for local damage mechanisms and hence mechanical properties.