Analysis of Fiber Flow, Fiber Orientation, and Void Formation at Syringe-Nozzle Junction in Material Extrusion Additive Manufacturing of Short Carbon Fiber Epoxy Composites

Abstract

Material extrusion additive manufacturing of short carbon fiber epoxy composite ink should exhibit thixotropic behavior which enables the fabrication of complex as well as simple 3D structures with controlled and tailored fiber arrangement within the composite part. This study investigates a method to automatically segregate fibers from voids and epoxy allowing fiber flow analysis and fiber orientation distribution. Validation of this method is used to present the experimental results for fiber orientation/alignment and void formation at the syringe-nozzle junction for a stitched (entire cross-section) and representative image. Further, the results were compared to assess the significance of the stitched image analysis over a representative image. Specimens were extracted as is from the syringe-nozzle juncture, followed by polishing and imaging. Qualitative visualization and quantitative analysis of the cross-section of the fibers were carried out using image-processing techniques for both images to identify the fiber orientation and alignment corresponding to the ink material flow direction at this junction. Bay and Tucker's method was used to quantitatively measure the 3D orientation and alignment of fibers. Similarly, qualitative, and quantitative analysis was carried out to identify and measure void area fraction for both the images. This study provides insight into the fiber alignment, arrangement, and dispersion within the epoxy matrix at this section as the ink material flows into the nozzle, followed by extrusion. Lastly, the experimental results reported in this study could be used to validate computational models used for analyzing flows within the ME-AM system for short fiber-reinforced epoxy composites.