Additive Manufacturing of Highly Filled Fiber Reinforced Ceramic Matrix Composites

Abstract

Ceramic matrix composites (CMCs) are commonly used in aerospace components that require resistance to high temperature environments. CMCs can be manufactured using a variety of methods including silicon infiltration, chemical vapor deposition, and polymer pyrolysis, but there are challenges with the cost and time associated with them. Additive manufacturing techniques have shown promise as a method to produce CMCs with polymer pyrolysis because they can reduce the manufacturing time and allow for a more tailored design of the part, but it is challenging to construct parts with high fiber loadings that can retain their geometric accuracy. This research aims to create and characterize photocurable formulations with high fiber content that can be 3D printed. To do this, photocurable mixtures of preceramic polymer resins were synthesized. They were then filled with pitch and polyacrylonitrile (PAN) based milled fibers with lengths of 50 μm and 100 μm respectively from 0-40 wt.%. The cure depths of these specimens were measured by leveraging a custom technique, and it was found that they varied from 0.58-1.07 mm depending on the fiber and formulation. Extrusion tests were also performed with material at various fiber loadings and based on the fiber length. Successful extrusion was achieved at 25-30 wt.% and 35-40 wt.% for the 100 μm and 50 μm length fibers respectively. It was found that mixtures up to 40 wt.% were photocurable and extrudable, yet there is room for improvement on the resin stability which will be pursued in future work. However, the photocurable, high fiber content ceramic resins produced in this work show promise for constructing custom CMCs for aerospace applications, such as components on rocket nozzles and thermal protection systems.