Nanoporous Carbon Nanotube Coating for 3D Printing of High-Performance Continuous Fiber Reinforced Polymer Composites

High strength and lightweight continuous carbon fiber reinforced composites are desirable structural materials for applications in various industries including aerospace, automotive, and defense. Additive manufacturing (AM) of such important materials may provide multiple benefits including reduced cost, improved manufacturing efficiency, and the ability to fabricate complex structures not possible with traditional methods. Despite these benefits, a significant challenge with AM of continuous carbon fiber composites is poor impregnation of the fiber bundle with matrix material. When there is a lack of matrix material, voids develop within the fiber bundle and reduce mechanical properties of the composite including strength and stiffness. To minimize void formation, low speed manufacturing is typically necessary to facilitate impregnation. In this work, it was shown that fiber bundle impregnation can be significantly improved by applying thin, nanoporous coatings to the continuous fiber bundle. Using an electrophoretic deposition process, the coating microstructure, including thickness and nano pore size, was easily controlled through effective tuning of process parameters. Ultimately, individually coated carbon fibers were obtained and provided improvements in fiber bundle impregnation without sacrificing the flexibility of the fiber bundle. A highly absorbent yet flexible fiber bundle was desirable for 3D printing applications and would facilitate fabrication of complex geometries. With such tailored nanoporous coatings, fifteen-fold improvement in resin absorption time due was observed due to improved wicking by the nanoporous structure. Such improvements in absorption characteristics have a great potential for drop on demand or other resin-based 3D printing techniques. Furthermore, mechanical characterization demonstrated the potential of nanoporous coatings for additive manufacturing of high performance carbon fiber reinforced composites.