Phenolic-Impregnated Carbon Ablators (PICA) Modelling for Spacecraft Structures Under High-Temperature Applications

In the aerospace applications varying from spacecraft re-entry vehicles to rocket propulsion systems demand robust thermal protection against extreme temperature. Accurate modeling of charring ablation is critical for reliable virtual testing, reducing dependence on costly ground experiments. Previous finite element studies using Arrhenius-based kinetics reproduced surface temperatures reasonably well but consistently overpredicted surface recession, underscoring the sensitivity of predictions to assumed constant parameters. This study presents the first implementation of isoconversional kinetics using the Flynn–Wall–Ozawa (FWO) method for one-dimensional PICA torch test simulation within Abaqus finite element environment. Multi-rate thermogravimetric data were reduced to obtain conversion-dependent activation energy and pre-exponential factors, which were tabulated and embedded into UMATHT. Results show that FWO kinetics improve predictive fidelity by lowering recession errors by 47% (frozen) compared to Arrhenius, while reducing surface temperature by 60–120 K and keeping it within the experimental 2250–2500 K band across 0.6–1.6 kg/(m²·s). However, the temperature profile and the recession rate could not be simultaneously reproduced by a single heat transfer coefficient, highlighting the shortcomings of bulk-pyrolysis kinetics and indicating the need for refined boundary modeling or inclusion of surface chemistry effects. Overall, the FWO framework represents a more realistic upgrade to Arrhenius formulations, reducing conservatism in TPS simulations and improving predictive fidelity in Abaqus.