Novel Fiber-Reinforced Polysiloxane Composites: Processing, Characterization, and Modeling for Hypersonic Applications

Novel fiber-reinforced polysiloxane composites (FRPCs) using various fibers infiltrated with a high char yield polysiloxane resin were developed and tested under extreme aerothermal environments. Techneglas manufactures the preceramic polysiloxane resin. FRPCs using glass, silica, carbon, graphite, carbon/polybenzimidazole, alumina, and quartz fibers in different architectures were manufactured by the Koo Research Group. Characterization of thermal stability, flammability, ablation, thermophysical, and mechanical properties of these FRPCs was performed. Thermal stability properties of these FRPCs were characterized using thermogravimetric analysis, and flammability properties using microscale combustion calorimetry. Ablation properties using an oxy-acetylene test bed with advanced diagnostics were performed at several heat fluxes and exposure times. Recession rate, mass loss rate, front surface temperature, and back-face heat-soaked temperature are criteria to compare material performance. The microstructures of these pre- and post-tested FRPCs were investigated using scanning electron microscopy and micro-computed tomography. Thermophysical properties of these FRPCs in virgin and char states were characterized at elevated temperatures. Using these material properties and surface thermochemistry analysis, material response modeling was performed and validated with aerothermal test data. The composites’ tensile, compression, and flexural properties were conducted via ASTM standards. These FRPCs compared favorably with legacy phenolic-based ablatives under similar extreme aerothermal environments.