<p>The damping behaviour of polymer nanocomposites which are doped with graphene nano-platelets (GNPs) can be attributed mainly to the interactions between the GNPs and the polymer matrix, as well as to the matrix inherent damping capability. Furthermore, additional mechanisms like interlayer friction between GNP layers that form the GNP flake seem to play a crucial role. However, as the GNP content increases, this leads to agglomeration which reduces the effective surface area in contact with the polymer, lowering the interfacial friction and, consequently, damping. Moreover, excessive GNP content increases the stiffness of the nanocomposite, which can reduce the polymer’s ability to deform and dissipate energy through internal friction. Similar to polymer nanocomposites, the same damping mechanisms take place during carbon fibre reinforced composite (CFRP) damping where additional energy dissipation related to the interaction between the carbon fibres and the GNPs are identified. Nevertheless, for both material cases, there is an optimal concentration of GNP for which damping is maximized due to a balance between enhanced interfacial interaction and energy dissipation. Several specific analyses, qualitative and quantitative, are proposed here as plausible explanations of the damping behaviour observed in these composites.</p>