This experimental and theoretical study systematically investigates the structural, chemical, mechanical, and kinetic behavior of Tyranno fibers subjected to high-temperature exposure. Fibers were heat-treated in an argon atmosphere from 1200 °C to 1500 °C and characterized using FTIR, XRD, TGA, SEM, and mechanical testing. The experimental findings revealed a significant reduction in mechanical performance—with tensile strength and Young's modulus decreasing markedly—that correlated with microstructural and chemical transformations. TGA measurements showed a complex, multi-stage thermal decomposition, which was accurately validated using a simulated kinetic model. Furthermore, the crystallization kinetics, observed via XRD, were successfully described by a Johnson–Mehl–Avrami–Kolmogorov (JMAK) model, providing quantitative insight into the nucleation and growth mechanisms. Collectively, the results highlight a crucial trade-off: high-temperature treatment enhances the thermal and chemical stability of Tyranno fibers by promoting crystallization, but it simultaneously degrades their mechanical properties due to defect formation and porosity. By combining experimental characterization with theoretical modeling, this work provides a comprehensive understanding of the degradation mechanisms, offering valuable insights for optimizing the use of these fibers in demanding aerospace and structural applications.
Lafdi et al. (Sat,) studied this question.