Sandia Labs FY21 LDRD Annual Report

FY21 ANNUAL REPORT

Polymers in extreme environments examined with novel experimental and computational tools. Polymer surfaces and interfaces, common in myriad engineered systems as insulators

and protective coatings, must survive extreme environments. Researchers constructed a test chamber at Sandia’s Ion Beam Laboratory to bombard polymers with controlled doses of electron beam irradiation, allowing ionization and thermal effects to be studied independently, and changes in composition to be observed. Using polyethylene as a test case, the team developed computer models to account for rapid transformations arising from charge accumulation associated with X-ray or electron backscattering, photoionization, chemical decomposition, thermomechanical shock, temperature- dependent spall fracture, and phase change. These expanded capabilities for evaluating material survivability will allow a broader use of polymers and other complex materials in engineered systems. (PI: Nathan Moore)

Intensity map of fluorescence from a polyethylene specimen while its surface is bombarded with electrons (region is several millimeters across).

Rapid physics-informed survivability assessments. Producing methods that simplify, automate, and streamline the tasks associated with survivability assessments to facilitate agile concept exploration is an important part of mission work. This LDRD project leveraged Sandia’s production codes to ensure long-term support for the underlying capabilities. The work included modeling an experiment in which a material sample is exposed to radiation at a facility such as the Z machine or the National Ignition Facility, specifically focusing on the thermal and thermo-mechanical responses of the sample. The team also evaluated the radiation environments where materials used in electrical devices subject to radiation should be tested. This method of modeling allows for assessment of detailed mechanical responses, such as velocity, stress, and strain, as well as metrics for understanding radiation response of electrical devices, such as dose, dose rate, and damage. A user interface simplifies the evaluation by providing a constrained set of options for using the underlying physics codes. Workflows automate the evaluation by coordinating input setup, executing code, transferring data transfer between codes, and processing results. Documented exemplars demonstrate the general applicability of the tools for survivability assessments. (PI: Brian Franke)

An exemplar survivability problem in which a spectrum filter and material sample are exposed to radiation at a test facility. Analysts may wish to rapidly assess the effects of variability in the spectrum, materials, and layer thicknesses.

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LABORATORY DIRECTED RESEARCH & DEVELOPMENT