Session: 03-01-02: Annual Conference-Wide Symposium on Additive Manufacturing

Paper Number: 149000

149000 - Composition-Process-Property Relationships for Direct-Ink-Writing of Polymer Nanocomposite-Type Precursors 

Polymer composite-type precursors consist of a polymer binder matrix and functional particle fillers. These precursors are widely used in the manufacturing of parts from various material classes including polymer composites, ceramics and metals, with appropriate post-processing steps such as debinding and sintering. Most conventional manufacturing methods that process these precursors are high-throughput approaches that lack in precise control of constituent morphology, and thus the final microstructure and functional properties in the manufactured parts. Additive manufacturing methods, specifically direct-ink-writing is an effective manufacturing method to process these precursors as it has been shown to be capable of controlling material microstructure in each deposited filament. Particularly, fillers are known to align under the influence of shear and extensional deformation of the composite inks. Comprehensive understanding of this phenomenon relies heavily not only on ink rheology but also the interaction between the ink and the nozzle. The latter manifests in the form of wall-slip and is often overlooked during modeling and analysis of the direct-ink-writing process. Recent work has shown that wall slip is highly prominent for highly loaded composite inks and smaller nozzles. Presence of wall-slip generally induces plug flow in the nozzles, significantly reducing the shear flow within the precursor, limiting the microstructural control capability. Despite this general understanding, detailed studies are needed on how ink composition and process parameters such as nozzle size and flow rate influence the balance between shear flow and wall-slip and, in turn the final microstructure and properties of printed parts.

 

 In this study, we investigate the direct-ink-writing of various polymer composite type precursors, specifically polyethylene oxide- graphene-EGaIn composites and a ceramic precursor including Zirconium diboride particles in a preceramic polymer. We elucidate how the ink composition and printing process parameters influence the wall-slip velocity and true shear strain rate and in turn, the printed part microstructure and electrical conductivity. This is achieved through combining data from the capillary rheometry using a dual-purpose DIW printhead and rotational rheometry along with microstructural and electrical characterization of 3D printed structures. The influence of ink composition on various flow mechanisms and part properties were statistically analyzed, by distinguishing between process-dependent and process-averaged (compositionally inherent) effects. It was shown that reducing particle loading promoted reduced wall slip and increased shear alignment producing structures having comparable functional properties with structures printed with higher particle loading. Key observations have been made regarding the potential particle alignment under the effect of various wall slip mechanisms. Results of this work will be critical towards ink and process design for direct-ink-writing of polymer nanocomposites.

Presenting Author: Arda Gozen Washington State University

Presenting Author Biography: Dr. Arda Gozen is the George and Joan Berry Associate Professor at the School of Mechanical and Materials Engineering of Washington State University. He obtained his Ph.D. degree in mechanical engineering in 2012 from Carnegie Mellon University where he also worked as a post-doctoral research associate. Prior to his Ph.D. studies, Dr. Gozen obtained his B.S. degree from Middle East Technical University, Ankara, Turkey. He is the recipient of 2019 NSF CAREER and WSU Voiland College of Engineering and Architecture Junior Faculty Research awards. He is the author of over 30 journal publications, numerous conference proceedings and holds 2 patents. His research interests include micro- and nano-scale manufacturing, soft-materials and rheology, flexible-stretchable devices, mechatronics and instrumentation, dynamic systems and controls and, precision engineering.

Authors:

Ruchira Tandel Washington State Universit
Caitlin Grover Washington State University
Arda Gozen Washington State University