Electrical Investigation by Tunneling Atomic Force Microscopy of Carbon Fiber-Reinforced Panels Manufactured by Modified Resin Film Infusion

The purpose of this work is the detection of the electrical current map by tunneling atomic force microscopy (TUNA) of carbon fiber-reinforced panels (CFRPs). The impregnation of the CFRPs is carried out through a multifunctional epoxy formulation containing glycidyl polyhedral oligomeric silsesquioxane (GPOSS), for improving flame resistance, and multiwall carbon nanotubes (CNT) to contrast the electrical insulating properties of the epoxy resin. The multifunctional panels are manufactured by an appropriately modified resin film infusion (RFI) process. The effects of the different ply numbers (seven, 14, and 24) on the TUNA electrical performance are assessed. In particular, TUNA technique, which is able to detect ultralow currents ranging from 80 fA to 120 pA, allows to identify the conductive paths due to CNTs. The CNTs result firmly anchored to the carbon fibers of the fabric layers. The adopted manufacturing process allows the transit of the nanofilled resin avoiding filtration effects. TUNA's current images highlight the presence, in the interlayer space of carbon fibers, of conductive three-dimensional networks of CNTs through the plies. This occurrence ensures good electrical properties of the multifunctional panels, which results suitable for advanced structural applications.