Additive manufacturing of continuous carbon fiber/thermally curable thermoset composites

Abstract

Continuous carbon fiber-reinforced thermoset composites are widely valued for their exceptional strength-to-weight ratio, thermal stability, and structural performance, which are critical features in aerospace, automotive and marine applications. However, conventional manufacturing methods such as hand lay-up, vacuum bagging and resin transfer molding are labor-intensive, geometrically restrictive, and expensive, limiting design flexibility and scalability. Composite additive manufacturing (AM) offers a transformative alternative by enabling mold-free and layer-wise fabrication, which allows greater geometric freedom, part customization, and minimizes material waste. Despite these advantages, producing complex thermoset composite geometries with high mechanical performance via AM remains challenging due to the slow curing kinetics and rapid viscosity reduction of thermoset matrix upon heating, as well as the absence of effective crosslinking density at interlayer regions. ☐ To overcome these limitations, this research introduces a core-shell tow-preg-enabled AM strategy for continuous carbon fiber composites. The system uses a thermally curable epoxy core impregnated into fiber tows, encased in a UV/thermal dual-cure resin shell. UV exposure rapidly solidifies the shell for shape retention, while subsequent thermal curing achieves high crosslink density across layers. This dual-curing process enhances interlaminar bonding, structural cohesion, and enables the creation of geometrically complex architectures without molds. ☐ The fabricated composites achieve a fiber volume fraction exceeding 50%, with outstanding mechanical properties: tensile strength of 1295.7 MPa, compressive strength of 544.1 MPa, flexural strength of 659.3 MPa, and interlaminar shear strength of 50.9 MPa. The process also demonstrates rapid shape retention and low void content. ☐ This core-shell AM approach presents a scalable and versatile solution for manufacturing advanced thermoset composite structures, unlocking new capabilities for lightweight, high-strength components in demanding engineering applications.