3D printing of continuous carbon fiber reinforced thermoset composites using UV curable resin

Abstract Additive manufacturing is trending toward functional applications beyond the scope of rapid prototyping. This requires the development of high‐performance, lightweight, and complex structures resulting from additive manufacturing. One of the biggest challenges for fulfilling these requirements is the limitation of material properties. The introduction of reinforcement allows for the expansion of current polymer‐based 3D printing technologies to achieve increased material properties while maintaining complex geometries. Commercial 3D printers able to print thermoplastic composites have recently been demonstrated with good repeatability. However, limitations of these thermoplastic composites include low fiber volume fraction and susceptibility to high temperatures. In contrast, thermoset‐based composites offer greater thermal stability and higher mechanical performance due to the cross‐linked structure of the polymer. Moreover, using continuous reinforcement instead of short fiber reinforcement offers higher performance opportunities. Therefore, the challenge of 3D printing with continuous fiber‐reinforced thermoset composite is addressed in this study. A 3D printer capable of printing a UV curable resin system reinforced with continuous carbon fiber was constructed. Variations of printed composites' mechanical properties depending on the fiber tow characteristic were investigated. Two different carbon fiber types and their associated tow twist count and sizing were evaluated in this study. Burn‐off tests were used to determine the printed composites' final fiber volume fraction. Using a rule of mixtures approach, strength and modulus were predicted for each composite and compared against their experimental values. Predicted modulus values were found within 2%–5% of experimental, while strength values were significantly less than predicted.