Additive manufacturing of continuously reinforced thermally curable thermoset composites with rapid interlayer curing

Research on different methods to achieve composite additive manufacturing has accelerated in the last decade. Existing commercial equipment on the market can only fabricate carbon fiber composites using thermoplastic or a narrow range of rapid curable resins (photopolymerization and frontal polymerization), which cannot meet a wide range of mechanical and durability requirements. Here, we developed a Rapid Interlayer Curing Assisted (RICA) 3D printing strategy, by in-situ formation of a dual-cure resin system to enable an interpenetrating network (IPN) at the interlayer in between thermally curable resin/fiber laminates to achieve fast solidification and shape retention in 3D printing, and then subsequently forming a complete polymerization of major matrix resin (e.g., epoxy) across the interlaminar in post-baking. This concept allows to use any types of commercially available thermally curable resin and fibers to develop 3D printed composites. We developed a robotic system consisting of a uniquely designed end effector and an automated robot arm, yielding a composite 3D printer that enables us to print continuously reinforced thermally curable thermoset composites. The printed composite achieved fiber volume fraction at similar to 44.2 vol%, tensile strength at 1075.27 MPa and modulus at 45.24 GPa, flexural strength at 1209.50 MPa and modulus at 68.01 GPa, and interlaminar strength at 37.17 MPa.