Multi-material additive manufacturing of self-heating structures for out-of-autoclave post-processing and de-icing

This work describes a method for 3D printing self-heating structures by embedding conductive layers inside a thermoplastic matrix using a dual-nozzle setup. The method uses a suspension of carbon nanotubes and short carbon fibres, which self-assembles into a thin conductive film after evaporation of the solvent. The embedded resistive heater can generate over 200 °C and can be controlled by adjusting the electrical current, voltage, and by modifying the suspension with epoxy resin or a blend of polyvinylidene fluoride and acrylic polymers. A conductive layer with 5 wt. % of epoxy resin generated up to by 63 °C, while it was 134 °C with the same amount of the polyvinylidene fluoride and acrylic blend. The method preserves the design freedom and allows to embed complex conductive shapes into a polymer matrix. The resistive heater creates a temperature gradient upon heating across the thickness of the 3D-printed structure, and it can be tailored by adding more resistive heaters into the composite. Joule heating can be employed to obtain void-free composite structures without an autoclave. The heating remained effective in cold temperatures, although the generated temperature at −60 °C was 34 % lower than during heating in room temperature. The results show that 3D-printed self-heating structures have better design and multi-material capabilities than traditional manufacturing methods, while maintaining Joule heating performance.