Sustainable and self-regulating out-of-oven manufacturing of FRPs with integrated multifunctional capabilities

With the ever increasing demand for energy reduction to stimulate sustainable development, new energy efficient manufacturing processes for advanced fibre-reinforced plastics (FRPs) are of great interest to overcome limitations of conventional autoclave or oven based manufacturing processes such as high energy consumption and size restrictions. Herein, a highly energy efficient and safe out-of-oven curing method is presented by integrating a pyroresistive surface layer with intrinsic self-regulating heating capabilities, into a composite laminate. This surface layer consists of a nanocomposite film based on graphene nanoplatelets (GNPs) and high density polyethylene (HDPE) and possesses self-regulating Joule heating capabilities, which can be used to cure epoxy based composites at a desired temperature without the risk of over-heating. Moreover, the thermoplastic nature of the surface layer enables easy fabrication with good flexibility for complex shapes. Compared to state-of-the-art out-of-autoclave oven curing, the proposed out-of-oven Joule heating approach consumed only 1% of the energy required for curing, with no effect on mechanical performance and glass transition temperature (T_g) of the final composite. Moreover, the integration of the self-regulating heating layer offers additional functionalities to the cured composites, like strain or damage sensing as well as the potential of de-icing without affecting the internal structure and performance of the laminate. The presented smart heating layer provides a novel solution for sustainable manufacturing as well as real-time structural health monitoring (SHM) throughout the components’ life for multifunctional composite applications in the field of renewable wind energy and aerospace.