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

尽管金属的增材制造正在彻底改变材料和由其制成的部件的设计，但测量的机械性能，如强度和韧性，表现出显著的分散，导致不可预测和潜在的灾难性失效行为。该奖项支持基础研究，以阐明增材制造金属中少量纳米填料如何增强机械性能，从而提高可靠性并实现广泛的工程应用。这一进展可能会改变3D打印技术，并激发美国制造业的竞争力。此外，本研究将培养材料设计、材料力学以及多尺度实验和计算等多学科领域的研究生和本科生。研究结果也将成为面向K-12夏令营学生的3d打印纳米复合材料未来航空航天材料新系列讲座的基础。空洞缺陷的存在会降低材料性能，并在材料内部引入性能变化，这是增材制造金属的固有弱点。为了克服这一限制，本研究旨在研究氮化硼纳米管对增材铝基体的增强作用，因为纳米管-金属界面存在多尺度强化和增韧机制。在原位电子显微镜的帮助下，通过纳米力学拔出嵌入在增材制造金属薄膜中的单个纳米管，可以直接量化不同工艺条件下的界面强度。无法通过实验获得的纳米管-金属界面细节，如在纳米管-金属界面形成的复杂反应产物，将通过密度泛函理论计算来表征。纳米管-基质界面特性以及加工过程中产生的基质孔隙率测量结果将被纳入具有代表性的体积元有限元模型，以进一步阐明增材制造纳米复合材料试样的破坏机制。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.