This Faculty Early Career Development (CAREER) award supports a fundamental investigation into the molecular alignment that occurs in nanoscale fibers during post-processing. Strong polymer fibers are the building blocks for lightweight and high strength materials useful in a wide variety of industries. Researchers have studied and optimized conventional microscale fiber manufacturing and post-processing methods for many years to maximize fiber stiffness and strength. Polymer nanofibers have the potential for higher normalized strength than larger conventional fibers due to the physics associated with their small fiber diameter. However, conventional post-processing approaches are difficult to integrate with nanofabrication methods such as electrospinning, making the effects of post-processing on polymer nanofiber strength not well understood. Implementation, investigation, and optimization of conventional post-processing methods for electrospinning have the potential to realize ultra-strong, lightweight polymer nanofiber and polymer-derived carbon nanofiber material. These materials would benefit key industries and our society by reducing energy costs, increasing safety, and making it possible to build larger structures and faster vehicles, vessels, and air/spacecraft. Project execution will provide advanced training in nanotechnology and materials science and engineering to graduate and undergraduate students. The associated outreach activities will expose elementary and high school students to engineering and science to promote the pursuit of STEM education and careers.
The objective of this award is to investigate the macromolecular-level structural transition of polymer nanofibers during drawing and the resultant mechanical properties. Methodologies will be established to process both individual nanofibers and low density aligned polymer nanofiber mats under independently controlled parameters including cure time prior to stretching, processing temperature, and stretch rate. Process/structure/property relationships will be established to investigate the effects of polymer chain mobility, molecular weight and fiber diameter in relation to maximum elongation of the nanofibers. The influence of fiber-fiber junctions on strain for low density non-woven mats will be modeled and tested experimentally to determine the importance of post-stretching individual polymer nanofibers versus an assembly of nanofibers. These studies will provide evidence of polymer nanofiber strength development during drawing as well as the effect of scale on polymer fiber post-processing.
