Collaborative Research: Exploiting Nanoscale Interfaces to Enhance Bulk Mechanical Response of Additively Manufactured Boron Nitride Nanotube-Metal Composites

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Although additive manufacturing of metals is revolutionizing design of materials and the parts made from them, the measured mechanical properties, such as strength and toughness, exhibit significant scatter, leading to unpredictable and potentially catastrophic failure behaviors. This award supports fundamental research to elucidate how small percentages of nanofillers in additively manufactured metals enhance the mechanical properties, thus improving reliability and enabling widespread engineering use. This progress could transform 3D printing technologies and invigorate the manufacturing competitiveness of the United States. Additionally, this research will train a diverse group of graduate and undergraduate students in the multidisciplinary areas of materials design, mechanics of materials, as well as multiscale experiments and computations. The research results will also form the basis of a new lecture series on 3D-printed nanocomposites as future aerospace materials for K-12 summer camp students.The presence of voiding defects, which degrades material performance and introduces property variations within the material, is an inherent weakness of additively manufactured metals. To overcome this limitation, this research aims to investigate the reinforcement of additively manufactured aluminum matrices with boron nitride nanotubes because of the multiscale strengthening and toughening mechanisms emanating at the nanotube-metal interface. The interfacial strength under different processing conditions will be directly quantified by nanomechanical pull-out of individual nanotubes embedded within additively manufactured metal films, with the help of in situ electron microscopy. The finer nanotube-metal interfacial details that are not accessible by experiments, such as the complex reaction products formed at the nanotube-metal interface, will be characterized by density functional theory calculations. The nanotube-matrix interfacial properties together with matrix porosity measurements arising from processing, will then be incorporated into finite element models of representative volume element to further elucidate the failure mechanisms of the additively manufactured nanocomposite specimens.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.