Experimental studies on liquid additive mixing in a hyperbolic die to incorporate liquids in polymer based additive manufacturing

• Published in: AIP conference proceedings Vol. 2139; no. 1
• Main Authors: Sangli, Aditya, Arispe-Guzman, Marcelo, Armstrong, Connor, Bigio, David
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Melville American Institute of Physics 26.08.2019
• Subjects: Additive manufacturing; Additives; CAD; Carbon fibers; Castor oil; Computer aided design; Computer simulation; Deformation effects; Droplets; Fillers; Imagery; Liquids; Miscibility; Morphology; Polymer matrix composites; Polymers; Production methods; Velocity gradient
• ISSN: 0094-243X; 1551-7616
• DOI: 10.1063/1.5121695

Additive manufacturing methods currently use solid fillers in the polymer matrix to make composites. Many researchers have studied the effect of die design on solid fillers like glass and carbon fibers but there is no research on incorporating immiscible liquid additives which can lead to additive manufacturing of solid parts with a controllable immiscible liquid morphology internal to the part. To accomplish this, experiments must be done to determine the effect of die design on the deformation induced on an immiscible droplet in the flow field. In this research, the feasibility of using shear flows and extensional flows to deform a droplet is first studied. A channel with walls based on a hyperbolic equation can impose a constant stretch rate at the center and makes it easier to model the flow. Applying this principle, a converging channel is built, filled with Silicone oil (Matrix liquid) and subject to hyperbolic flows. The deformation seen by a droplet of immiscible Castor oil is studied for various positions of injection using high speed imagery. It was observed that droplets injected at the center of the channel did not see any significant stretch but the ones injected closer to the walls stretched and reached the affine state. Simulations studies were performed using ANSYS Fluent to find the velocity gradients along each streamline where the droplet was injected. This data, combined with the droplet widths measured from the images, was used to track the Capillary number changes for a given droplet. It was observed that droplets with a higher initial Capillary number saw a steeper reduction than droplets with lower initial Capillary numbers. Further, close examination of the droplet dimensions from each image showed that the droplet width reduced and reached an asymptote in the channel. These results aid in understanding liquid filler behavior in a polymer flow and helps in incorporating liquids in polymer based additive manufacturing.