Preliminary Mechanical Analysis of Carbon-Carbon Composites Exposed to High-Temperature Flow

Carbon–carbon composites remain a leading candidate for thermal protection systems in hypersonic vehicles due to their high-temperature stability and favorable strength-to-weight characteristics. Although their thermal resistance is well documented, the evolution of viscoelastic mechanical properties following short-duration, high-enthalpy exposure remains insufficiently understood. This gap is critical, as changes in stiffness, damping capacity, and microstructural integrity directly influence structural survivability during repeated thermal loading. This study presents preliminary results quantifying how high-enthalpy flow affects the mechanical response of C/C composites. Test specimens were exposed at approximately 1600 K in the HyperReact facility at the Propulsion and Energy Research Laboratory for several durations. Pre- and post-exposure mass measurements were used to quantify ablation, allowing the extent of material recession to be related directly to subsequent changes in viscoelastic response. Subsequently, Dynamic Mechanical Analysis was employed to measure storage modulus, loss modulus, and tan(δ) across a temperature sweep, enabling correlation between material removal mechanisms and viscoelastic behavior. The observed variations in stiffness and altered damping characteristics indicate that high-enthalpy exposure produces mechanically consequential degradation pathways not captured by traditional ablation metrics alone. These findings motivate expanded mechanical characterization for carbon– carbon materials used in hypersonic thermal protection systems and rotating detonation engine components, as both environments impose rapid and extreme thermal environments that cause matrix degradation, reduce mechanical stiffness, and limit service life.