Multimode Ultrahigh Strain Rate Investigations into the Fundamental Mechanics of Polymers

由于其固有的微观结构，聚合物是运动装备和防护甲等耐冲击结构中必不可少的材料。然而，由于对这类材料在超高应变率应用中具有优异性能的机理的基本理解存在差距，进一步的应用进展是有限的。该奖项支持研究，通过使用冲击波来机械地快速加载材料，同时使用光谱学来观察分子结构的行为，从而获得关于聚合物如何响应动态加载的基本见解。所产生的知识将加速基于工程聚合物的耐震结构的开发，其性能比目前使用的结构更高。这项研究的洞察力将拓宽聚合物在过去未预见到实现的场景中的应用领域。从长远来看，该项目的成果还将改善现有应用中的能量吸收性能，如动作运动防护装备，以及增强地面、空中和海上车辆的耐撞性。因此，这项研究不仅将推动科学的进步，而且由于聚合物在耐震结构中的重要性，也将推动吸能结构的发展。这项研究最重要的是通过集成先进的光学、材料科学和工程以及机械工程的多学科方法。此外，这项研究致力于培训不同群体的学生工程技术和人际交往技能，并有助于灌输下一代工程师，以保持美国的全球技术竞争力。该奖项将为本科生和高中生提供实践研究经验，通过本科生和研究生的课内和课外活动整合研究和教育，扩大女性和少数族裔学生的参与，并通过大学开放参观更广泛的社区。由于高应变率加载聚合物而导致的失败机制仍不明确。为了克服这一科学挑战，这项研究努力在揭示分子间运动和输入的多轴冲击波之间的相互作用以及它们对固有键强度的影响方面取得突破。实验方法依赖于利用聚合物对太赫兹波的透明度，这提供了同时耦合加载和表征设置的能力，以同时揭示作为加载模式、幅度和应变率的函数的聚合物的原位动态行为。这些结果将提供对导致控制聚合物行为和性能的内在故障机制的分子间运动的洞察。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。

Polymers are essential materials in shock-tolerant structures such as sports gears and protective armors due to their intrinsic microstructure. However, further advancements towards their use are limited due to the gap in the fundamental understanding of the mechanisms dedicating the superior performance of this class of materials in ultrahigh strain rate applications. This award supports research to gain fundamental insights on how polymers respond to dynamic loading through the use of shock waves to mechanically and rapidly load the material while using spectroscopy to observe the behavior of the molecular structure. The knowledge generated will accelerate the development of engineered polymer-based, shock-tolerant structures with higher performance than those currently in use. Insights from this research will broaden the application domain of polymers in scenarios where their implementations were unforeseen in the past. In the longterm, the outcomes of this project will also lead to improved energy absorption performance in existing applications such as action sports protective gears and enhanced crashworthiness of ground, aerial, and marine vehicles. Thus, the research will not only promote the progress of science, but due to the importance of polymers in shock-tolerant structures will promote the development of energy absorbing structures. Paramount to this research is the multidisciplinary approach through the integrating of advanced optics, material science and engineering, and mechanical engineering. Additionally, this research strives to train a diverse group of students in technical and interpersonal skills of engineering and contribute to inculcating the next generation of engineers to maintain the global technological competitiveness of the United States. This award will provide hands-on research experiences to undergraduate and high school students, integrate research and education through undergraduate and graduate intra- and extra-curricular activities, broaden the participation of women and minority students, and outreach to the broader community through university open-houses.Failure mechanisms due to high strain rate loadings of polymers remain ambiguous. To overcome this scientific challenge, this research strives to provide a breakthrough in revealing the interplay between intermolecular motion and incoming multi-axial shock waves and their effect on the intrinsic bond strength. The experimental approach hinges on leveraging the transparency of polymers to terahertz waves, which provides the ability to couple loading and characterization setups at the same time to uncover the in-situ dynamic behavior of polymers as a function of loading mode, amplitude, and strain rate simultaneously. The results will provide insights into the intermolecular motion leading to the intrinsic failure mechanisms governing the behavior and performance of polymers.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.