Insights into Spallation Mechanisms of Thermal Protection System Materials from Mass Spectrometry and HyMETS Testing

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An effort was undertaken to investigate the mechanisms responsible for internal pressure build up within thermal protection system (TPS) materials subjected to high-enthalpy environments. Understanding how gases evolve, migrate, and interact with the microstructure of a TPS is essential for predicting degradation and failure modes such as spallation. To this end, complementary experimental approaches were employed that provided both chemical and mechanical insight into subsurface processes.

Chemical evolution and internal pressure buildup were identified using the processes illustrated in Figure 1. In part A, in-depth pressure measurements obtained during testing in the Hypersonic Materials Environmental Test System (HyMETS) quantified the dynamic buildup of subsurface pressure as gases evolved. In part B, mass spectrometry was applied to characterize volatile species released as the TPS decomposed under heating.