Development of High-Fidelity Material Response Modeling for Resin-Infused Woven Thermal Protection Systems

The primary objective of the research was to advance the predictive capability for modeling woven thermal protection systems (TPS), in particular, the Heatshield for Extreme Entry Environment Technology (HEEET), a dual-layer woven TPS developed at the NASA Ames Research Center. The accomplishments and results can be divided into three aspects. First, a constrained optimization approach was used to infer an orthotropic thermal conductivity model for HEEET. Specifically, the model provides thermal conductivity properties for HEEET in the 295 - 2000 K temperature range in all three orthogonal directions for both layers of the HEEET material. When using the inferred thermal conductivity model, higher fidelity simulations can be performed, producing results that are in much better agreement with experimental measurements. The model will continue to be used in future simulation efforts to guide the design of HEEET and TPS for space exploration missions. Second, the manufacturing process for HEEET has changed in recent years, which has led to observable changes in the stiffness properties. Again, a constrained optimization approach was applied to infer room temperature stiffness properties, as well as properties at elevated temperatures. The properties at elevated temperatures result in a stiffness reduction model that can be used in simulations involving combined thermal and mechanical effects, increasing the predictive capability of modeling HEEET in a multiphysics environment. The stiffness reduction model will be particularly useful in future simulation efforts to guide the design of HEEET and TPS for space exploration missions. Finally, a linear elasticity solver was developed to model the effects of mechanical loading on thermal protection systems. The linear elasticity solver was implemented within a thermal response solver in a coupled manner, allowing for modeling the simultaneous effects of thermal and mechanical loading on TPS. Specifically, the coupling allows for the computation of deformation due to increased temperature as well as applied mechanical loading. The coupled solver will continue to be used to guide design, research, and TPS developmental efforts for future space exploration missions. These unique research contributions will be very useful for guiding future design, research, and experimental efforts of HEEET and woven TPS.