## 1 Introduction
These nanoparticles are promising nanomaterials in gas- or liquid-barrier applications because graphene sheets do not allow the diffusion of small gases or liquids through their plane. To fulfil this function, films with special architecture can be employed as lightweight protective coatings for composites [30]. Nanoarchitectures with a high level of nanoplatelet orientation and high nanofiller content (>50 vol%) ensure a high tortuosity factor, resulting in high barrier and low permeability properties [31; 32]. Recent studies showed that highly aligned graphene fillers in polymeric coatings can reduce transmission rates by nearly 400 times compared to neat polymer [33]. Further, films at 80 wt% nanofiller content showed a reduction of the WVTR of nearly 90% [34]. Moreover, GNP films with this architecture are also employed for other applications. Indeed, the intrinsic properties of the nanoplatelet (i.e., good thermal and electrical conductivities) are scaled on the macroscale when assembled in a well oriented nanostructure. GNP films have been widely used in thermal management applications [35; 36], such as heating elements in innovative de-icing systems [37; 38], thermal barrier coatings of carbon fibre composites and heat spreaders in battery packs [39], thanks to the high thermal conductivity, which can vary between 600 to 3200 W/mK according to the production process [40]. Additionally, films with a good orientation and superposition of GNPs ensure high electrical conductivity (in the order of 10\({}^{3}\)-10\({}^{5}\) S/m) and can be used as electromagnetic shielding materials [41]. Indeed, [PERSON] et al. reported that the well-aligned structure of GNP films is not only beneficial for high electrical conductivity but also favourable for multiple internal reflections of electromagnetic waves, resulting in a shielding effectiveness of about 90 dB [42]. Thin and highly conductive GNP films are also employed to reduce the effects of lightning on composite aircraft, reducing delamination [43; 44]. [PERSON] al. demonstrated that a highly electrically conductive graphene coating on the surface of carbon fibre composites facilitates lightning's electrical current to spread out without significant damage [45]. In this work, the authors investigated the possibility of employing high-content nanocomposites made with GNPs as a protective layer for reducing moisture absorption. GNP films with high filler content have been integrated into Kevlar/epoxy panels in a one-step manufacturing process. Panels have been fabricated with protective layers at different filler contents (70, 80, 90 wt%). The effectiveness of protection against water uptake has been investigated through moisture uptake and GAG tests in an environmental chamber and the level of damage in the panels has been investigated with non-destructive inspection (NDI). Results indicate that GNP films are effective in protecting the panel from moisture, with a reduction of the maximum absorption after 40 days of 30%. The easy integration of these films in the manufacturing process of composites in a co-curing process ensures a reduction in the processing time and improves energy savings.