Investigating Ohmic Heating as a Method of 3D-Printing Freestanding Thermoset Composites

Continuous fiber-reinforced (CFR) thermosetting composites are integral to aerospace and high-performance engineering due to their superior specific strength, stiffness, and thermal resistance; however, conventional manufacturing methods are labor-intensive and ill-suited for rapid prototyping or complex, one-off designs. While additive manufacturing (AM) offers a promising alternative, current 3D printing approaches for CFR composites are predominantly limited to thermoplastic matrices and require support structures, constraining their applicability for structurally demanding and high-temperature environments. This work introduces a novel method that integrates direct ink writing (DIW) with in situ ohmic heating to enable the additive manufacturing of freestanding CFR thermoset composites. In this approach, a continuous carbon fiber tow serves dual functions: a mechanical reinforcement and a resistive heating element, to thermally cure an epoxy matrix in real-time during deposition. A modified coaxial nozzle was developed to extrude the composite filament and apply Joule heating through the fiber, allowing for rapid curing and unsupported printing without external heat sources or support materials. Proof-of-concept structures, including inclined spans and step geometries, were successfully fabricated, demonstrating the capability of this method to produce complex, self-supporting parts. The results reveal that this approach enables rapid, support-free printing of CFR thermoset composites, presenting a scalable and cost-effective solution for manufacturing high-performance components in aerospace and related fields.