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

虽然金属的添加制造正在彻底改变材料和由它们制造的部件的设计，但测量的机械性能，如强度和韧性，表现出显著的分散性，导致不可预测的和潜在的灾难性故障行为。该奖项支持基础研究，以阐明在附加制造的金属中加入少量纳米薄膜如何增强机械性能，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，并增强美国的制造业竞争力。此外，这项研究将在材料设计、材料力学以及多尺度实验和计算等多学科领域培训一批不同的研究生和本科生。这些研究成果也将成为为K-12夏令营学生提供的关于3D打印纳米复合材料作为未来航空航天材料的新系列讲座的基础。孔洞缺陷的存在降低了材料的性能，并导致材料内部的性能变化，这是添加制造的金属的固有弱点。为了克服这一局限性，本研究旨在研究氮化硼纳米管对添加制造的铝基体的增强作用，这是因为纳米管-金属界面具有多尺度的强韧化机制。不同加工条件下的界面强度将通过嵌入在添加制造的金属薄膜中的单个纳米管的纳米机械拔出来直接量化，并借助于原位电子显微镜。纳米管-金属界面的精细细节，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-基质界面属性以及加工过程中产生的基质孔隙率测量结果将被纳入代表性体积元素的有限元模型中，以进一步阐明添加制造的纳米复合材料样品的失效机制。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.