CAREER: Multi-scale Mechanical Behavior of Quantum Dot Nanocomposites: Towards Data-driven Automatic Discovery of High-performance Structures

这项教师早期职业发展（Career）资助将支持包含超小二维量子点纳米颗粒的热固性纳米复合材料的加工-结构-力学关系的基础研究。热固性聚合物用于航空航天、国防、运输、电子和许多其他行业。此外，纤维增强热固性复合材料主导高性能结构应用。尽管热固性塑料用途广泛，但它们很脆。另一方面，量子点纳米颗粒同时增强了热固性材料的韧性和强度。然而，我们不知道超小的二维粒子是如何增强热固性材料的力学性能的。该研究项目将通过系统模拟和实验揭示这些增强的分子起源。这种新知识具有潜在的变革性，因为量子点可以增强所有其他大规模填充复合材料，如连续纤维、石墨烯和碳纳米管复合材料。教育目标是打造开源虚拟现实工程教育工具，培养创新工程师。我们计划开展独特的合作设计项目，以提高学生的创造力，从而影响下一代工程师的创新潜力。外展活动还将在为硅谷代表性不足的群体服务的小学/高中进行。本研究将提高我们对量子点纳米复合材料分子水平损伤/变形机制和宏观断裂行为的认识。一个特定的重点是给予独特的亚20纳米结构，包含多达三个不同的量子点尺寸，可以与热固性反应和彼此。在CAREER奖期间，将使用实验，理论，计算和信息学方法的组合来回答：(a)量子点纳米复合材料如何变形和断裂？(b)它们的主要增韧机制是什么？研究目标是：(i)揭示载荷传递和脱粘机制，（ii）确定塑性变形、损伤起裂和损伤积累机制，以及（iii）观察、量化和模拟含20 nm以下多模态尺寸量子点的热固性材料的增韧机制。为了实现这些目标，将进行分子动力学合成和力学测试。将进行正电子湮灭时间光谱、原位拉曼光谱、原位同步加速器x射线表征和非原位力学测试。分子动力学多尺度模型将用于量化增韧行为。此外，将创建一个新的原子数据驱动的预测框架，以快速发现具有高机械性能的纳米复合材料。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。

This Faculty Early Career Development (CAREER) grant will support fundamental research on processing-structure-mechanics relationships in thermosetting nanocomposites containing ultrasmall two-dimensional quantum dot nanoparticles. Thermosetting polymers are used by aerospace, defense, transportation, electronics, and many other industries. Moreover, fiber reinforced thermoset composites dominate high-performance structural applications. Despite their common use, thermosets are brittle. Quantum dot nanoparticles, on the other hand, simultaneously enhance the toughness and strength of the thermosets. Yet, we don’t know how the ultrasmall two-dimensional particles enhance mechanical properties of the thermosets. The researched project will reveal the molecular origins of these enhancements using systematic simulations and experiments. This new knowledge is potentially transformative because quantum dots can enhance all the other larger-scale-filler composites, such as continuous fiber, graphene, and carbon nanotube composites. The education objective is to create open-source virtual reality engineering education tools and cultivate creative engineers. Unique collaborative design projects are planned to enhance student creativity that can impact innovation potential of the next-generation engineers. Outreach activities will also be performed in the elementary/high schools that serve underrepresented groups in the Silicon Valley.This study will improve our understanding of molecular level damage/deformation mechanisms as well as macroscopic fracture behavior of quantum dot nanocomposites. A specific focus is given to unique sub-20 nm structures containing up to three different quantum dot sizes that can react with thermosets and with each other. During this CAREER award, a combination of experimental, theoretical, computational, and informatics approaches will be used to answer: (a) How do quantum dot nanocomposites deform and break? (b) What are their main toughening mechanisms? The research objectives are to (i) reveal the load transfer and debonding mechanisms, (ii) identify the plastic deformation, damage initiation, and damage accumulation mechanisms, and (iii) observe, quantify, and model the toughening mechanisms in thermosets containing multi-modal size quantum dots below 20 nm. To achieve these objectives, molecular dynamics synthesis and mechanical tests will be performed. Positron annihilation time spectroscopy, in-situ Raman spectroscopy, in-situ synchrotron X-ray characterization, and ex-situ mechanical tests will be performed. A molecular dynamics-informed multi-scale model will be used to quantify the toughening behavior. In addition, a new atomistic data-driven predictive framework will be created to quickly discover nanocomposites with high mechanical performance.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.