Multimode Ultrahigh Strain Rate Investigations into the Fundamental Mechanics of Polymers

聚合物由于其固有的微观结构而成为耐冲击结构（如运动装备和防护装甲）的基本材料。然而，由于在对这类材料在低应变率应用中的上级性能的机制的基本理解方面存在差距，因此限制了它们的进一步应用。该奖项支持研究获得聚合物如何响应动态加载的基本见解，通过使用冲击波对材料进行机械和快速加载，同时使用光谱学观察分子结构的行为。所产生的知识将加速开发基于聚合物的耐冲击结构，其性能比目前使用的结构更高。这项研究的见解将拓宽聚合物在过去无法预见的情况下的应用领域。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，例如运动防护装备和增强地面，空中和海上车辆的耐撞性。因此，这方面的研究不仅将促进科学的进步，而且由于聚合物在耐冲击结构中的重要性，将促进吸能结构的发展。这项研究的最重要的是通过整合先进的光学，材料科学与工程，机械工程的多学科方法。此外，这项研究致力于培养一批多样化的学生在工程技术和人际交往能力，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，扩大妇女和少数民族学生的参与，并通过大学开放日推广到更广泛的社区。聚合物高应变率载荷的失效机制仍然不明确。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入射多轴冲击波之间的相互作用及其对内在键强度的影响方面提供突破。实验方法取决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，以同时揭示聚合物作为加载模式，振幅和应变率的函数的原位动态行为。该奖项反映了NSF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。

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.