PROCESS MODELING OF THE FIRST PYROLYSIS CYCLE OF SMP-10 CERAMIC MATRIX COMPOSITES

Abstract

Ceramic matrix composites (CMCs) are widely used in high-temperature applications like hypersonic thermal protection systems. The polymer infiltration and pyrolysis (PIP) process is commonly employed to manufacture CMCs. The PIP process consists of repeated cycles of preceramic polymer infiltration and pyrolysis to progressively increase the density of CMCs. However, it presents challenges such as gas evolution, shrinkage of the preceramic polymer (PCP), and the formation of cracks, porosity, and internal stresses during pyrolysis. Detecting these defects is difficult, and they can lead to interlaminar delamination, reducing the CMC structure's strength, stiffness, and durability. Currently, determining the number of PIP cycles and manufacturing parameters relies heavily on experimental results due to the complex nature of CMC manufacturing. However, the high costs and time required for experiments hinder process optimization. Thus, there is a need for high- fidelity computational tools that can capture PIP process defects and analyze the effects of manufacturing parameters. This research aims to develop a multiphysicsbased model with temperature and degree of cure dependencies to simulate the first pyrolysis cycle of the PIP process and its resulting defects (pores and cracks) in CMCs. The FEA software ABAQUS and user subroutines will be used to implement this model. A comparison will be made between the predicted defects by the computational model and experimental results from AFRL. A comprehensive multiphysics model will be developed, integrating a thermo-chemical model, thermo- mechanical model, and crack initiation and propagation model. Initial findings have demonstrated encouraging agreement between the material model and thermogravimetric analysis (TGA) data, particularly concerning the impact of temperature and ceramic conversion.