Evaluation of UV Curable and Highly Loaded Inks for Additive Manufacturing of Ceramic Matrix Composites

The next generation of advanced aerospace technologies will require strong materials able to withstand high temperatures in high stress environments. Ceramic matrix composites (CMCs) are becoming more popular solutions used to manufacture components for these challenging environments. CMCs take advantage of the high temperature capabilities and erosion resistance of ceramic materials combined with a fiber reinforcement matrix to enhance the strength beyond the capabilities of pure ceramics. Traditionally, CMCs are manufactured using a variety of methods including silicon infiltration, chemical vapor deposition, and polymer pyrolysis, but there are challenges with the available geometries, cost, and time associated with them. Additive manufacturing techniques have shown promise as methods to produce CMCs that can allow for a more tailored design of components and a reduced manufacturing time. However, it is challenging to construct parts with high fiber loadings that can retain their geometric accuracy and compare to more traditional methods of manufacturing CMCs. This research aims to develop and characterize photocurable CMC formulations and CMC inks with high fiber content that can be 3D printed. To do this, photocurable mixtures of preceramic polymer resins were synthesized and filled with pitch and polyacrylonitrile (PAN) based milled carbon fibers from 0-40 wt.%. Additional inks were mixed and tested without photocuring capabilities at solids loadings up to 65 wt.% to evaluate the printing capabilities of highly filled inks. Cure depth of photocurable inks, extrudability of each mixture, rheology of highly filled mixtures, and printing results were obtained. While photocuring CMC inks had a limit to its effectiveness at high solids loadings, a printable mixture with greater than 50 wt.% fiber reinforcements was shown to be viable. The results shown in this paper have significance for future work in additive manufacturing of fiber filled polymer inks and show promise to construct CMCs for aerospace applications.