Designing Tough Composite NanoFibers using Brittle Glasses

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Designing Tough Composite NanoFibers using Brittle GlassesNon-technical SummaryThis award supports theoretical and computational research and education on composite materials, which are mixtures of two or more pure substances. Composites are ubiquitous in everyday life and can be found in commercial airliners, electric cars, consumer electronics and medical equipment/devices. The common wisdom of composite design is that a property, say ductility, of a final composite mixture must be within the range of values taken by the constituent pure substances. Therefore, in order to toughen a brittle material, the general practice is to incorporate a ductile material to form a composite. The research goal of this NSF project is to seek a new composite design paradigm such that the resulting composite can be superior to any of the pure constituent substances. That is, can one design a tough composite using only brittle constituents? The research team will conduct large-scale atomic-level simulation of thousands of potential composite designs and apply state-of-the-art machine-learning algorithms to optimize such composite design. With this new composite design, brittle materials can potentially be used in load-bearing structural composites, while functional materials can sustain higher stresses without mechanical failure. The educational efforts will include outreach in collaboration with the "New Visions: Math, Engineering, Technology & Science (METS)" high-school program and developing interactive learning modules using the Wolfram Computable Document Format (CDF) environment for core engineering undergraduate courses.Technical SummaryThis award supports theoretical and computational research and education on designing composite materials. Most materials lack highly desirable work-hardening mechanisms, so that oxide glasses and superhard solids generally cannot be used as structural materials, and silicon-based electronics cannot bend or survive impacts. The primary motivation is to devise a general toughening scheme to impart work-hardening to brittle materials by combining them into composites by exploiting stiffness disparity. To accomplish this goal, the research team will carry out large-scale molecular-dynamics simulations exploring the design space of the composite nanofibers, which will be used as a training dataset for state-of-the-art machine-learning algorithms. The composite nanofiber designs from this project, capable of work-hardening, can be used to synthesize tough nanofibers as reliable probes for characterization, data-storage or nano-fabrication, as well as building-blocks for macroscopic fibers, fabrics or scaffolds. In addition, the design strategy and toughening mechanisms for composite nanofibers can be applied to toughen bulk composite, which could open-up a new paradigm for structural materials. Importantly, with the new composite designs, brittle materials (low-cost silicate glasses, as well as superhard materials) can potentially be incorporated into structural composites. Using the tough fiber design, functional materials and devices can tolerate both local strains (volume expansion in lithiation or thermal shock) and global strains (service strain in flexible electronics or accidental drops).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.