Researchers from Colorado State University and Arizona State University have developed a new additive manufacturing (AM) method for fabricating high-performance carbon fiber-reinforced thermoset composites. Published in Nature Communications, the study introduces a tool-free process using in-situ thermal curing via photothermal conversion, enabling rapid, energy-efficient 3D printing without post-processing or support structures.
The technique combines a thermoresponsive DCPD resin with a low-power blue laser mounted on a robotic platform to locally heat carbon fibers during printing. This allows the composite material to cure instantly upon deposition, supporting the creation of both continuous and discontinuous fiber-reinforced structures in midair or on solid substrates.
Rapid, tool-free composite manufacturing
Traditional manufacturing of fiber-reinforced polymer composites (FRPCs) requires custom tooling and long oven-cure cycles, limiting scalability and design freedom. To overcome these constraints, the researchers employed ring-opening metathesis polymerization (ROMP) of dicyclopentadiene (DCPD) to formulate a fast-curing, tunable thermoset resin. When deposited, the resin is cured on demand by laser-induced photothermal heating of carbon fibers, which act as localized heat conductors.
Using a 4.5W laser diode (450 nm), the team achieved rapid heating rates (~220–240 °C within 200 ms) at print speeds of up to 1.5 m/min. The paper notes that higher print speeds (>2 m/min) require more powerful lasers. Still, the method enabled fabrication of structures with up to 70 vol% for continuous fiber composites and void content as low as 0–1.5%, all without oven curing or support materials.
Mechanical performance and energy savings
The study demonstrated mechanical parity between in-situ printed parts and conventionally cured counterparts. Flexural tests showed that parts printed with aligned fiber orientations achieved comparable modulus but slightly lower flexural strength compared to oven-cured samples. Dynamic mechanical analysis confirmed similar glass transition temperatures (Tg ~160 °C) across all samples.
A key demonstration involved printing a two-layer composite bracket in 100 seconds using just 0.45 kJ of thermal energy. By comparison, a similar epoxy composite cured in a laboratory oven would consume an estimated 6912 kJ over six hours, highlighting the significant energy efficiency of the process.
Freeform printing and scalability
The researchers successfully printed continuous fiber composites along curved, unsupported paths using a robotic arm, achieving precise deposition across multiple substrates over distances of up to 1.8 meters. This opens up possibilities for large-scale, freeform composite structures in aerospace, marine, and automotive applications.
Preliminary demonstrations with aramid fibers suggest broader applicability to a range of reinforcement types and geometries.
Curing breakthroughs and support-free strategies reshape composite 3D printing
Recent advances in resin formulation and curing strategies have expanded the capabilities of additive manufacturing, particularly for high-performance and support-free applications. Previously, researchers from Colorado State University demonstrated frontal polymerization to fabricate support-free carbon fiber parts, marking an early step toward in-situ composite curing.
Separately, researchers at Lawrence Livermore National Laboratory developed a dual-wavelength resin system that enables simultaneous printing of structural and sacrificial supports, streamlining post-processing. In parallel, companies like Formlabs are refining photopolymer resins and curing systems to achieve injection molding-grade performance in 3D printed components. The in-situ photothermal curing method introduced by Dojan et al. builds on these developments, offering a tool-free, scalable approach to fabricating fully cured thermoset composites.
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Featured image shows Schematic representation of the additive manufacturing process. Image via Dojan et al., Nature Communications.
