Adaptative electrothermal activation of hybrid composites for anti-icing function

A green flexible film heater is integrated into fiber-reinforced panels to activate the anti/de-icing function through electrical power. The heater is composed of nanometric graphitic layers embedded into a polyvinyl-alcohol (PVA) thermoplastic matrix. The influence of PVA molecular weight (M.W.) on electrical conductivity and heating efficiency is investigated. For the same nanofiller percentage (50%), the electrical conductivity decreases as the M.W. of the hosting matrix increases, going from 926.0 (M.W. 30 ÷ 70 kDa) to 8.5 S/m (M.W. 146 ÷ 186 kDa). This different behavior, which also affects heating efficiency, is due to the peculiar arrangement of polymeric chains between the nanofiller layers. The M.W. of PVA sensibly affects this arrangement, even leading to the intercalation of polymer chains between graphitic layers that prevents them from arranging into a crystalline lattice, causing complete PVA amorphization. Due to the preservation of the nanometric electrical paths in the polymeric network, unlike metal wire heaters, the film heater retains its heating function after damage. A centimeter-sized perforation does not break all electrically conductive paths, leaving the heating function active. The energy required to heat the developed functional fiber-reinforced panels is significantly lower than that of traditional electrothermal systems, saving up to 88.5% of energy. A traditional repair method for accidental damage, such as the “hot bond repair”, is considered, and a modified methodology, allowing restoration of the heating function, is proposed.