The slight reduction in GNP electrical conductivity post functionalisation (detailed in 0) has no discernible effect on the conductivity of the composite. The neat epoxy electrical conductivity is 6.1 x 10 11 S m -1 and no significant change is observed with the addition of any filler. This indicates that no percolative network is formed, meaning that higher loadings than those tested are required to achieve an electrically conductive composite. Having considered how the different filler surface chemistries lead to different fillermatrix dispersions, the effect of these can be linked to the multifunctional composite properties. The mechanical reinforcement from a nanoplatelet filler to a nanocomposite under tensile stress can be understood using shear-lag theory . Whereby the deformation of the surrounding matrix generates an axial shear stress on the filler particle, that builds from zero at its edges to a maximum at its centre. This stress-transfer requires a large enough platelet over which the filler and matrix axial stresses can equilibrate, and a high matrix shear modulus (and thus 𝐸 𝑚 ) to efficiently transfer the force. The former requires graphene platelets with a lateral size of at least 3 µm , and the latter means that stiffer matrices unlock higher 𝐸 𝑓 values . The overall reinforcing effect is then dependent on the amount of matrix each filler platelet can affect, i.e., the shear-lag unit. Maximising this requires well dispersed and distributed, high aspect ratio flakes . The PG-10 and PG-NH retain their platelet shape in the matrix, and the lateral size of the flake stacks appear to follow the distribution found for the powder. However, the stacks of the former are thicker than the latter, resulting in a lower aspect ratio and thus lower effective surface area and weaker reinforcement. The PG-CF flakes do not preserve their platelet shape, and instead form amorphous aggregates, with a higher density of low lateral size (< 2 µm) particulates. These are not long enough to bear the tensile load from the surrounding matrix, and as such are ineffective at mechanical reinforcement, leading to the lowest 𝐸 𝑐 values.