Development of Graphene-based Nanocomposites for Radar Absorbing Materials

Novel graphene-based nanocomposites, consisting of a polymeric-based system filled with graphene nanoplatelets (GNP) are developed for application as low-cost lightweight electromagnetic shielding materials. A significant challenge in radar absorbing materials (RAM) technology is the development of lightweight absorbing materials with frequency selective properties for EM shielding and EM decoupling among radiating systems and antenna arrays. In fact, frequency selective radar-absorbing materials (FS-RAM) would allow the selective EM shielding of a specific frequency simultaneously providing low-reflectivity, which is a key-requirement in the case of multiple systems installed in closed bays, in order to avoid hot spots, as well as the case of open-sites, in order to avoid coupling between radiating antennas and EM shielding configurations. This work presents a series of strategies to obtain graphene-based nanocomposites with improved electromagnetic, electrical and mechanical properties. The main scope of this study is the scale-up of the fabrication processes, towards large-scale aeronautical distribution. To this purpose the use of commercially available GNP-powders are investigated, and incorporated into different thermosetting and thermoplastic resin systems. The complex dielectric permittivity of the resulting composites is studied in the frequency range between 8-12 GHz, and fitted through a novel multiscale Maxwell Garnett-based model that can estimate the agglomeration state of the nanofiller. The results show that the different electromagnetic and mechanical behaviors of the final composites, are conditioned by the interaction between the GNP in the different resins systems, and the filler concentration, as illustrated by scanning electron microscopy (SEM), and Raman spectroscopy.