Direct effects of UV irradiation on graphene-based nanocomposite films revealed by electrical resistance tomography

The integration of surface sensing elements providing an in situ monitoring of the UV-induced degradation effects in composite materials and structures is crucial for their applications in hostile environments characterized by high levels of radiation, such as space. In this work, the electrical response of a novel UV-sensitive nanocomposite film was investigated using electrical resistance tomography (ERT). The conductivity changes measured at the irradiated surfaces were compared with results from morphology analysis by scanning electron microscopy (SEM) and surface analytical techniques, such as Raman microscopy. Highly conductive and UV-sensitive nanocomposite coatings were prepared by embedding the graphene and deoxyribonucleic acid (DNA) component in a poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) matrix. The coatings were deposited onto carbon-reinforced laminated structures fabricated by resin transfer molding process using an aerospace-grade epoxy resin. Two different irradiation conditions were tested by exposing the nanocomposite surfaces to UV-C irradiances of 2.6 and 4.0 mW/cm2. Results show that the ERT technique has great potential for the in situ health monitoring of carbon-based materials and structures for aerospace applications, which are subject to degradation by UV-C radiation: it allows mapping of the conductivity changes occurring at the surface of the graphene/DNA/PEDOT:PSS coatings during irradiation.