Determination of Carbon-Carbon Hydrocode Parameters by Uncertainty Quantification

Material models utilized by hydrocode programs (EPIC, Velodyne) require dynamic material properties and strengths as input. Due to the scarcity of useable material databases, many times these properties are inferred by calibrating the hydrocode model to experimental results. The calibration process involves tuning the input parameters until the hydrocode results agree with the observed behavior. This uncertainty in dynamic material properties highlights the need for a robust and comprehensive methodology to converge on input properties with predictive capability. Under the Phase I SBIR program, Materials Research & Design (MR&D) and Southwest Research Institute (SwRI) successfully demonstrated an uncertainty quantification methodology and framework for hydrocode simulations; specifically, a hypervelocity projectile impacting a carbon-carbon (C-C) composite at elevated temperature. An empirical dataset was identified in the literature from which MR&D built a representative hydrocode model with. In coordination with MR&D, SwRI utilized the probabilistic software NESSUS to develop fast-running response surface models for the prediction of front and back damage areas as a function of nine material property values. These response surface models were then used to enable detailed variance-based global sensitivity analysis to characterize the dependence of the response quantities on the material property variations. Bayesian analysis was then used to refine the material property uncertainty distributions based on a comparison of the hydrocode simulation results with reported experimental result. Key findings of the Phase I effort were: fiber failure modes dominate the damage behavior of the C-C composite; calibrated fiber strengths are a function of proximity to the initial impact location, and thus dependent on loading rate; and better agreement with experimental data may be achievable with a strain-rate dependent constitutive model. In the Phase II effort, a well-established C-C material will be characterized for strain-rate and pressure dependent material properties. To do this, SwRI will conduct both split-Hopkinson pressure bar and flyer impact testing on the C-C composite, which will supplement MR&D’s constitutive modeling effort. SwRI will also conduct hypervelocity ballistic testing on C-C panels at elevated temperatures. To capture and quantify the damage sustained by the panels, multiple data collection methods will be used (high-speed cameras, CT Scans). These experiments will be used to mature the hydrocode-UQ methodology and enhance the capabilities of the toolset. At the conclusion of the Phase II effort, MR&D and SwRI will have created a methodology and analysis tool for the uncertainty quantification of hypervelocity impact on C-C materials, demonstrated using impact conditions analogous to thermal protection systems during hypersonic flight. Approved for Public Release | 20-MDA-10643 (3 Dec 20)