(202c) Radio Frequency Heating of Carbon Nanotube Composite Materials for Additive Manufacturing

Here, we report RF electromagnetic heating of polymer nanocomposite materials via direct contact and capacitively-coupled electric field applicators. Notably, RF heating allows nanocomposite materials to be resistively heated with applied electric fields. We highlight our novel RF heating technique for multi-walled carbon nanotube (MWCNT)/polymer composites and measure their broadband dielectric properties as a function of CNT loading. We also demonstrate two applications of this technique: (i) A key obstacle facing 3D-printed thermoplastic parts in engineering applications is the weak weld between successive filament traces, which often leads to delamination and mechanical failure. Here we report a novel concept for welding 3D-printed thermoplastic interfaces using intense localized heating of carbon nanotubes (CNTs) by microwave irradiation. We apply CNT-loaded coatings to 3D printer filament; after printing, microwave irradiation is shown to improve the weld fracture strength by 275%. (ii) We also demonstrate the use of RF heating to cure an automotive-grade epoxy loaded with MWCNTs. Our results show that lap shear joints cured faster with the RF method compared to control samples cured in an oven due to the heat transfer advantages of directly heating the epoxy composite.