Collaborative Research: Experimental and Computational Nanomechanics of the Load Transfer Mechanisms at the Graphene Polymer Interface

与传统聚合物复合材料相比，聚合物纳米复合材料在更低的填充成分重量下表现出显著的性能增强。石墨烯因其高刚度和高强度而被认为是聚合物中增强添加剂的理想候选者。然而，人们对石墨烯-聚合物界面的强度特性缺乏基本的了解。该合作研究奖支持基础研究，以提供对选定聚合物和石墨烯之间界面的应力传递过程的机理理解。这些工艺最终控制了石墨烯聚合物纳米复合材料的刚度、强度和韧性。这项研究将有助于实现轻、强、韧的聚合物纳米复合材料。这种先进材料将影响航空航天和汽车工业。这项研究跨越了制造、力学、材料科学和纳米技术等学科。这项多学科研究的成果将被纳入两所大学现有的本科课程。研究结果也将成为K-12夏令营学生的新系列讲座的基础，向这些有潜力的未来工程师介绍聚合物纳米复合材料作为下一代航空航天材料的主题。石墨烯-聚合物界面的强度特性对石墨烯基纳米复合材料的整体力学响应起着至关重要的作用。然而，在与石墨烯从聚合物基体中拉出相关的剪切变形过程中发生的复杂纳米级现象尚未得到很好的理解。该合作研究奖支持在纳米尺度上研究石墨烯-聚合物界面的变形、负载转移和破坏。采用互补的实验和计算相结合的方法。研究团队将使用独特的原位纳米力学表征技术，对嵌入聚合物基质中的单个石墨烯片进行拔出测试。纳米力学拉出实验将为界面强度特性提供直接和定量的测量。这些实验代表了一个重要的进步，比之前的宏观测量体复合材料的性能，石墨烯-聚合物的界面性质只能间接和定性地推断。与此同时，拔出试验的分子动力学模拟将在与实验相关的尺度上进行。这种互补的方法便于将实验结果与模拟结果进行比较。模拟将提供对实验无法获得的精细石墨烯-聚合物界面细节的见解，并将指导进一步的实验。这项互补的实验和计算工作将提供纳米级界面强化过程的机理理解，并破译嵌入石墨烯的尺寸和形态对石墨烯-聚合物界面机械强度的作用。

Polymer nanocomposites show substantial property enhancements at much lower filler component weight as compared to conventional polymer composites. Graphene has been considered an ideal candidate for reinforcing additives in polymers due to its high stiffness and strength. However, there is a lack of fundamental understanding of strength properties of graphene-polymer interfaces. This collaborative research award supports fundamental research to provide mechanistic understanding of the stress-transfer processes across interfaces between selected polymers and graphene. These processes ultimately control the stiffness, strength, and toughness of graphene polymer nanocomposite. This research will contribute towards achieving light, strong, and tough polymer nanocomposite materials. Such advanced materials would impact the aerospace and automotive industries. The research crosses the disciplines of manufacturing, mechanics, materials science, and nanotechnology. Results from this multi-disciplinary research will be incorporated into existing undergraduate courses at both universities. The research results will also form the basis of a new lecture series for K-12 summer camp students introducing these poetntail future engineers to the topic of polymer nanocomposites as next generation aerospace materials. The strength characteristics of graphene-polymer interfaces play critical roles in the bulk mechanical response of graphene-based nanocomposites. Yet, the complex nanoscale phenomena occurring during shear deformation associated with the pull-out of graphene from the polymer matrix are not well understood. This collaborative research award supports investigations of deformation, load transfer and failure of graphene-polymer interfaces at the nanoscale. A combination of complementary experimental and computational methods is employed. The research team will perform pull-out tests on individual graphene sheets embedded within polymer matrixes using an unique in-situ nanomechanical characterization technique. The nanomechanical pull-out experiments will provide direct and quantitative measurements of the interfacial strength properties. These experiments represent a significant advancement over prior macroscopic measurements of the bulk composite properties where the graphene-polymer interfacial properties can only be inferred indirectly and qualitatively. In parallel, molecular dynamics simulations of the pull-out tests will be conducted at size-scales relevant to the experiments. This complementary approach facilitates comparison between the results of experiments and simulations. The simulations will provide insights into the fine graphene-polymer interfacial details not accessible by experiments, and will guide further experiments. This complementary experimental and computational effort will provide mechanistic understanding of the nanoscale interfacial strengthening processes, and decipher the roles of the size and morphology of the embedded graphene on the mechanical strength of graphene-polymer interfaces.