Deformation and Failure Mechanisms in Carbon Nanotube–Metal Matrix Composites at High Strain Rates

碳纳米管-金属基复合材料是一类新型材料体系，具有较高的强度、硬度和抗冲击性，适用于航空航天、汽车、建筑、体育、航天等行业。例如，在制造过程中或在复合结构或部件的使用过程中，例如在动态运动接触和汽车碰撞中，会遇到高变形率。然而，碳纳米管-金属基复合材料在高速加载过程中的工作变形机制尚未得到充分的量化和理解。该奖项支持在多个尺度上的综合实验和计算研究，以发展基于假设的基本理解。所获得的知识将促进产品质量、可靠性、安全性以及碳纳米管-金属基复合材料的应用。此外，该奖项还支持课程改进，少数族裔学生参与暑期研究项目和长期项目，以及在STEM活动的公共设施进行实践示范。该项目的目的是了解碳纳米管与母材相比，如何在高应变速率下影响碳纳米管-金属基复合材料的机械性能和行为。为了实现这一目标，将执行多个相互关联的研究任务。任务1是利用激光增材制造技术合成母材和复合试样，并进行准静态力学表征。任务2是：(i)进行Kolsky bar实验以获得应力-应变关系，（ii）进行现场x射线成像以观察裂纹，（iii）表征由于Kolsky bar撞击导致的微观结构变化。任务3是：(i)进行弹丸撞击实验，测量Hugoniot弹性极限、动强度和冲击响应；（ii）表征撞击引起的结构变化；（iii）和（iv）进行流体动力学和分子动力学建模，分别了解宏观和原子尺度的冲击响应和耗散机制。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。

Carbon nanotube-metal matrix composites are a new class of material systems with desirable properties, such as higher strength, hardness, and impact resistance, making them suitable for applications in aerospace, automotive, construction, sports, space, and other industries. High- rate of deformation is encountered, e.g., in manufacturing processes or during service of the composite structures or parts, such as in dynamic sports contact and automobile collisions. The operative deformation mechanisms during high-rate loading of carbon nanotube-metal matrix composites, however, have not been adequately quantified and understood. This award supports integrated experimental and computational research at multiple scales to develop this fundamental understanding based on hypotheses. The knowledge gained will promote product quality, reliability, safety, and use of carbon nanotube-metal matrix composites applications. Furthermore, the award supports curriculum improvements, underrepresented minority student participation in summer research programs and long-term projects, and hands-on demonstrations at a public facility for STEM activities.The objective of this project is to understand how carbon nanotubes influence the mechanical properties and behavior of carbon nanotube-metal matrix composites at high strain rates, as compared to the base metal. To achieve this objective, multiple inter-related research tasks will be performed. Task 1 is to synthesize the base metal and the composite specimens by laser-based additive manufacturing and conduct quasi-static mechanical characterizations. Task 2 is to: (i) conduct Kolsky bar experiments to obtain stress-strain relations, (ii) perform in-situ X-ray imaging to observe cracks, and (iii) characterize microstructural changes due to Kolsky bar impacts. Task 3 is to: (i) conduct projectile impact experiments to measure Hugoniot elastic limit, dynamic strengths, and shock responses, (ii) characterize impact-induced structural changes, and (iii) & (iv) conduct hydrodynamic and molecular dynamic modeling to understand shock responses and dissipation mechanisms at the macro and atomic scale, respectively.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.