Thermogravimetric Analysis of Flexible Thermal Protection Systems for Thermal Response Modeling

Abstract

A multi-layered, Flexible Thermal Protection System (FTPS) heatshield configuration layup has undergone ground-based testing in an arc-jet facility to simulate heating generated during atmospheric entry. Thermogravimetric Analysis (TGA) was then performed on virgin samples of an aerogel felt insulator from this same FTPS layup configuration to characterize decomposition by obtaining its activation energy. Experiments were performed in an inert environment for Standard TGA and Modulated TGA methods using a TA Instruments Q5000IR experimental apparatus. Limited TGA testing resources in the past have resulted in rough approximations of activation energy of FTPS materials with little knowledge of uncertainty. A rigorous TGA testing campaign is set forth to experimentally determine the activation energy and its corresponding uncertainty for samples of aerogel felt to increase knowledge of the sample’s decomposition process. The activation energy and corresponding uncertainty obtained from both Standard TGA and Modulated TGA methods are compared. The activation energy from each method are inserted into an existing thermal response model that simulates heat transfer between layers of a FTPS layup. The resulting temperature traces are compared to thermocouple temperature data recorded during ground-based arc-jet testing to conceptually observe simulation accuracy. Recommendations for future testing and analysis are then summarized.