J.M. Pappas, X. Dong
Arizona State University,
United States
Keywords: additive manufacturing, carbon fiber composites, continuous fiber reinforcement, drop on demand, stereolithography
Summary:
Additive manufacturing of continuous carbon fiber composites provides many potential benefits by enabling fabrication of unique and otherwise difficult to manufacture composite structures. Through fiber-path planning, there is opportunity to customize 3D printed composites by aligning fibers along paths and curves to ensure maximum strength in highest stress areas, thus having greater potential for topology optimization over isotropic counterparts. Additionally, there is potential for manufacturing of advanced honeycomb, lattice and cellular structures, where fiber path planning enables fabrication of lightweight and high-strength composites with customizable properties to meet the needs of high-tech industries such as aerospace, automotive and defense. While there are many potential benefits to additive manufacturing of continuous fiber composites, there are also significant challenges. A primary challenge is void formation during the printing process which leads to poor interlayer bonding and significantly hinders the performance of printed composites. In this work we demonstrate that our combined fiber placement and stereolithography-inspired setup was capable of fabricating high-strength continuous carbon fiber composites by eliminating voids via resin infusion and consolidation. For this process, an aerospace-grade, dual UV and thermal curable photopolymer was pre-impregnated into continuous carbon fiber bundles immediately prior to fiber placement. Following fiber placement, voids were infiltrated with additional resin. Subsequent consolidation and UV-laser curing through a glass plate eliminated interlaminar voids and significantly improved interlayer bonding, as confirmed by microstructural and mechanical characterization. A thermal post-curing procedure ensured that resin was completely cured within fiber bundles and resulted in high-performance unidirectional composites with flexural strength and modulus reaching 1050 MPa and 61 GPa, respectively, at a fiber volume fraction over 40%. This work demonstrated that laser-stereolithography is readily suitable for fabricating high-performance continuous carbon fiber composites, if combined with fiber placement technology, and showed that there is potential for commercialization of such a combined apparatus. This is possible because laser-stereolithography machines are capable of infusing carbon fibers with photocurable resin, and curing the resin with a high-power UV laser through a glass plate that simultaneously provides in-situ consolidation of the 3D printed composite.