Multimode Ultrahigh Strain Rate Investigations into the Fundamental Mechanics of Polymers

San Diego State University Foundation, San Diego CA

Investigators

Abstract

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.