Sandia Labs FY22 Laboratory Directed Research & Development Annual Report

STRESS INTENSITY THRESHOLDS FOR DEVELOPMENT OF RELIABLE BRITTLE MATERIALS.

Brittle material failure can appear random and unpredictable at subcritical stresses. A fundamental understanding of how structural and environmental factors impact fracture propagation is necessary to predict fracture in these systems. Through this project, a physics-based model of glass fracture was developed to limit uncertainties in predicting crack growth. An experimental and computational approach composed of molecular dynamic (MD) simulations, numerical modeling, and atomic force microscopy (AFM) was used. AFM characterization identified crack growth rates as slow as 10-13 m/s. MD simulations identified the role of inelastic relaxation in crack propagation including evolution of the local atomic structure during relaxation. A numerical model for the existence of a stress intensity threshold was developed and is being incorporated into mission programs. The project included collaboration with faculty and students from Sandia Alliance partner Purdue University and with the Missouri University of Science and Technology. This work has resulted in five publications, with one, “ Inelastic relaxation in silica via reactive molecular dynamics,” selected for the cover of the Journal of the American Ceramic Society . PI Jessica Rimsza was also selected to

participate in the 7 th World Materials Research Institutes Forum Workshop for Early Career Scientists for her work on fracture in nuclear waste forms. (PI: Jessica Rimsza)

Cover of the Journal of the American Ceramic Society.

Three examples of inelastic relaxation in cracks propagation.

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LABORATORY DIRECTED RESEARCH & DEVELOPMENT