Christine Ajinjeru is a Ph.D. candidate in the Bredesen Center’s Energy Science and Engineering graduate program. She is working under the direction of Dr. Chad Duty at UTK and the Manufacturing Demonstration Facility (MDF) on determining the printability of thermoplastics and thermosets on various extrusion-based additive manufacturing (AM) platforms. Ms. Ajinjeru moved to the United States from Uganda via the United Kingdom in pursuit of a higher education and received a bachelor’s degree in chemistry at Grinnell College, Iowa, in 2014. While at Grinnell College, she participated in Oak Ridge National Laboratory’s (ORNL) Higher Education Research Experience’s (HERE) semester-long program, which introduced her to ORNL and the University of Tennessee.
Ms. Ajinjeru’s dissertation work is aimed at expanding the current selection of 3D printable materials for extrusion-based AM platforms. Developing new materials for AM requires screening across all areas of the printing process, from material selection to final part properties. She worked with her advisor, Dr. Chad Duty, on the first four-part framework that evaluates polymer feedstock as candidates for 3D printing across a variety of extrusion-based platforms. The framework uses thermal and rheological characterization to predict successful printability. For a successful print, pressure-driven flow of the melt through the nozzle must first occur. Additionally, the deposited material must form a stable bead with the right geometry, and the deposited bead must be able to support the weight of other subsequent layers and bridge a free spanning gap. Finally, the 3D printed structure needs to be dimensionally stable during the transition to the final part when cooling to ambient temperature.
Ms. Ajinjeru’s work delves into evaluating the applicability and effectiveness of the extrusion criteria to minimize costly trial and error. The pressure-driven extrusion criterion is modeled by calculating the necessary pressure required to extrude a material through a nozzle and comparing that to the system’s maximum pressure. Her work will provide a basis for both optimizing the use of current thermoplastic and thermoset materials as AM feedstock and guiding the development of new materials, especially high-performance materials.