This Faculty Early Career Development Program (CAREER) project will focus on improving the safety and performance of polymer composites by discovering the fundamental mechanisms governing the evolution of damage in these next-generation materials. Polymer composite usage is growing rapidly; driven by increasing demand for high-strength, lightweight materials in the automotive, aerospace, and civil infrastructure industries. In these primarily outdoor applications, loss of load-bearing ability over time is driven by material property changes in response to the complex and combined effects of mechanical and environmental stresses. A fundamental understanding of these changes is crucial to safe operation throughout the life cycle of the structure. To derive this understanding, the experimental approach in this research project takes advantage of changes in dielectric behavior of absorbed atmospheric water molecules in response to damage initiation and progression. By tracking the ability of water molecules to rotate in response to an oscillating electromagnetic field, early and non-visible changes in the chemical and physical characteristics of the material can be measured. The new and valuable insight into the mechanisms responsible for the progression of damage derived from these measurements will improve our ability to design more robust materials and better predict impending failure, thus advancing national health, prosperity, welfare, and national defense. The research will be complemented by an effort to provide access to K-12 summer engineering camp activities at North Carolina State University for students from rural and isolated urban communities. A sustainable process for packaging and disseminating these high-value educational resources will be developed and implemented, expanding their impact beyond the students attending the on-site camps and increasing visibility and knowledge of engineering among students who may not otherwise consider or pursue STEM careers.
The overarching goal of the research is to derive the mechanistic underpinnings of polymer composite damage progression across spatial scales in response to coupled thermal, hygroscopic, and mechanical loading. The specific objectives in support of this goal are to: (i) describe the link between water-polymer interaction and topology, nanovoid content, polarity, and hygrothermal aging of fiber-reinforced epoxies; (ii) connect the response of absorbed molecular water to multiscale damage induced by dynamic, fatigue, and impact loading; (iii) use a neural-network technique to extract the salient variables that govern damage progression for use in deriving a mechanistic understanding of the molecular precursors to damage; and (iv) reconcile the experimental and neural-network derived insights with the physical basis of state-of-the-art multiscale, multiphysics simulation techniques. This project will allow the PI to expand the knowledge base in mechanics and materials science, enabling safer and more efficient use of polymer composites across multiple industries.
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.