UES has been awarded a Phase I SBIR from the Air Force to investigate ceramic matrix composite (CMC) manufacture using the preceramic polymer infiltration and pyrolysis (PIP) method. During a pyrolysis cycle, there is a loss of matrix material as the polymer converts to a ceramic, such that multiple reinfiltration and pyrolysis cycles are required to maximize matrix density. While the first cycle typically uses a ceramic powder filled polymer, subsequent cycles do not. The final residual porosity can then depend on the stochastic variability of fiber placement in the original fiber preform, with some inter-tow spaces being larger than others such that incomplete filling results.
UES has teamed with Teledyne Scientific, both to access measured data on fiber placement in tested CMC's and to implement the knowledge gained here to improve the reliability of CMC's for hypersonic application.
Our two-fold approach uses a physical analog of CMC PIP processing to better understand the PIP process. We propose to use photopolymer-based additive manufacturing to build multiple identical models of a preform that has stochastically varied fiber placement, and then study their infiltration using poly vinyl alcohol in aqueous solution. Subsequent evaporation of the solvent will mimic the volume reduction associated with pyrolysis.
Guided by such a physical observation of the PIP process, we will work with Teledyne to mathematically model preform geometry and the subsequent polymer infiltration and pyrolysis, such that matrix filling of an actual ceramic fiber preform can be optimized.
A model that can optimize matrix filling for a PIP-processed CMC will be applicable to all CMC systems manufactured by PIP, including the CMC's of interest to our partner, Teledyne Scientific.