Collaborative Research: Fracture Mechanics of Glasses with Nanoscale Phase Separation - A Multiscale Experimental and Computational Study

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Although glasses exhibit unique properties, such as high strength and transparency, their inherent brittleness seriously limits their use in many practical applications. Extrinsic treatments can increase the toughness of glass but typically compromise its optical transparency. As an alternative route, this award supports fundamental research to elucidate how controlled nanoscale composition may be used to enhance the resistance to fracture of glass. This knowledge will accelerate the design of tough, yet transparent glasses. Insights from this study will promote glass as a competitive material for a broader range of applications, for which glasses have not been considered until now due to concerns related to safety and reliability resulting from their risk of fracture. Insights from this project will also lead to improved glass performance in many existing applications,for instance, lighter automotive windshields would result in significant energy savings. Thus, the research will not only promote the progress of science but due to the prevalence of glass will also advance the national health, prosperity, and welfare. By integrating multiple disciplines, including physics, material science, and mechanical engineering, this research will train a diverse group of students in various aspects of engineering and contribute to forming the next generation of scientists that the U.S. glass industry critically needs to compete globally. In addition, this award will support: inclusion of undergraduate students in research, integration of research and education through extensive collaboration with glass manufacturer Corning Inc., and recruitment of minority students and outreach to K-12 students through university programs Brittleness remains the main drawback of glasses. To overcome this age-old limitation, this research aims to elucidate the effects of nanoscale heterogeneities and controlled phase separation on the fracture toughness of calcium aluminosilicate glasses,an archetypical model for alkali-free display glasses. The bottom-up strategy relies on high-throughput molecular dynamics simulations, benefits from topological constraint theory, and culminates in peridynamic simulations to ensure the hand-shake of all the considered spatial scales: atoms, microstructure, and continuum. These predictions are systemically validated by experiments, which comprise structural analysis and mechanical tests. This interdisciplinary effort will offer some new insights in the thermodynamics and kinetics of phase separation in glasses. This new fundamental knowledge will serve as a guide to elucidate the distinct roles of the atomic topology, heterogeneity thereof, and nanoscale phase separation in controlling the nanoductility and macroscopic toughness of silicate glasses.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.