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The Washington Research Foundation Fellowship

Natalie Larson, Materials Science & Engineering, 2012-13 WRFF

Natalie LarsonMy first research experience at the University of Washington was in the Automobili Lamborghini Advanced Composite Structures Lab in the Aeronautics and Astronautics Department the summer before my freshman year. It was during this experience that I realized how much I loved working with carbon-fiber composites, particularly when I got to break them to determine their mechanical properties! While working in the Lamborghini Lab, I discovered my passion for materials science and engineering as I continually found myself excited to learn about how the fibers and matrix work together to create lightweight yet stiff composite structures.

The following year, I joined the Flinn Research Group and have been working in their lab ever since. During my sophomore year, I joined Gary Weber (graduate student) in working on Interpenetrating Polymer Networks as adhesives for advanced composite structures. Such adhesives are intended to improve composite structures fabrication and engineering in aerospace applications. For my second research project, I joined Ryan Toivola (graduate student) in investigating fluorescent probe-functionalized epoxy for use in non-destructive inspection of barely visible impact damage in aerospace composite parts. My independent role in this ongoing research is to characterize the effect of the epoxy’s elastic modulus on the response of the fluorescent probe to damage. I am very excited to be working on this fluorescent probe research, as it has the potential to allow in-situ structural health monitoring of composite aircraft.

I am grateful for my opportunities to conduct research in the Lamborghini Lab and the Flinn Lab, as they have helped prepare me for my future research endeavors in sustainable engineering in graduate school and beyond. I have had the opportunity to meet with leading scientists in composites engineering through this research and through the national SAMPE (Society for the Advancement of Material and Process Engineering) Conferences I have attended for the past two years. Most recently, I had the opportunity to present my research in the Student Poster Session at the National SAMPE Tech Conference in Charleston, SC. This trip was made possible by the support of the Washington Research Foundation. I would like to sincerely thank the Washington Research Foundation for supporting me as I continue with my research with fluorescent probes, as their generosity has and will afford me the opportunity to continue my research as well as present my results at conferences across the nation.

Mentor: Brian Flinn, Materials Science & Engineering

Project Title: Effect of Epoxy Modulus on Activity of a Fluorescent Dye for Aerospace Composite Damage Detection

Abstract: Non-destructive evaluation (NDE) of barely visible impact damage (BVID) in polymer composite aircraft structures is of high importance to the aerospace industry. Impact damage due to tool, bird, or luggage cart collisions can create defects below the material's surface, significantly reducing the mechanical performance. Such damage, termed BVID, forces engineers to over-design for BVID, adding significant weight to the aircraft. This over-designing is augmented by limitations in NDE, which currently force prohibitive aircraft downtime. The proposed research aims to develop a novel technique for quick, accurate, and cost-effective NDE of BVID during routine aircraft service, potentially allowing composites engineers to design lighter-weight airplane parts. The proposed NDE technique will integrate stimuli-dependent fluorescent dye molecules into epoxy aircraft coatings/matrices, utilizing fluorescence imaging technology. Under stress, the fluorescence behavior of the functionalized epoxy will change, allowing damaged regions of the composite to be located using a spectrometer. Currently, the research is focused on exploring the effects of integrating the fluorescent dye into epoxy systems, and understanding how fluorescence behavior is affected by the local conditions of the epoxy polymer surrounding the dye. As a part of this larger NDE development, the proposed research will focus on determining the effect of the epoxy's elastic modulus on the fluorescence behavior of the dye. Such research will help determine whether the dye should be incorporated into the matrix, coatings, or topcoats on the aircraft and may reveal the molecular mechanism of dye fluorescence. The proposed research consists of changing the modulus of epoxy with fillers and diluents, measuring the modulus of the epoxy, fabricating functionalized epoxy samples and measuring the fluorescence behavior of the dye under a range of mechanical stresses and local epoxy moduli. Results from this experiment will contribute to study in the fields of molecular engineering, composites, and NDE.