Ballistic and electromagnetic shielding behaviour of multifunctional Kevlar fiber reinforced epoxy composites modified by carbon nanotubes

Overall goal of the research is to develop a material simultaneously able to absorb mechanical shocks and shield from electromagnetic interferences. Several layered composite materials aimed at such multi-functionality have been conceived and realized: the characterization has been carried out in terms of electromagnetic shielding effectiveness in the range 0.8-8.0 GHz and of energy absorbing capability upon impact of metallic bullets fired at about 400 m/s and 1000 m/s (such velocity allows to explore the low energy range of potential mechanical shocks in aerospace structures). The composite specimens under test are ∼3.5 mm thick tiles made of hybrid multi-scale material: the manufacturing has been performed by integrating several layers of Kevlar fabric and carbon fiber plies within a polymeric matrix reinforced by carbon nanotubes. The electromagnetic shielding effectiveness has been measured by means of a reverberation chamber; the performances of the layered composites approach the metallic behavior with values of shielding up to 80 dB. The impact tests have been carried out by using an in-house built linear electromagnetic accelerator, known as railgun; the results show that a thin and light tile of the designed composite material is able to absorb high energy impacts with local delamination of the layered structure.