Mechanics of nozzle clogging during direct ink writing of fiber-reinforced composites

January 21, 2021

Brendan P. Croom (1), Andrew Abbott (1,2), James W. Kemp (3), Lisa Rueschhoff (1), Louisa Smieska (4), Arthur Woll (4), Stanislav Stoupin (4), Hilmar Koerner (1)

Additive Manufacturing, 37, January 2021. DOI: 10.1016/j.addma.2020.101701


Direct write; Nozzle clogging; Polymer matrix composite; Ceramic matrix composite; CMC; 3D printing


Nozzle clogging frequently occurs while printing fiber-filled polymer inks with extrusion-based additive manufacturing processes, which limits the quantity of fibers that can be added to the matrix, part fidelity, and geometric accuracy of the printing process. Both in situ X-ray radiography and ex situ X-ray computed tomography were used to explore the mechanisms that contribute to nozzle clogging. Three inks were considered, with fiber volume fractions ranging from 1% to 5.75%, and nominal fiber lengths from 150 to 470 µm. These results showed that the specific mechanisms that produced the clog depended substantially on the fiber volume fraction, fiber length and nozzle geometry. Specific clogging mechanisms included the log-jam pileup of misoriented fibers near the nozzle tip, the lodging of a fiber entanglement in the nozzle tip, and the accumulation of misoriented fibers at step-like reductions in the nozzle profile. Suggestions to reduce the prevalence of nozzle clogging are presented.

How Our Software Was Used

Dragonfly was used to isolate individual fibers in reconstructed tomograms.

Author Affiliation

(1) Materials and Manufacturing Directorate, Air Force Research Laboratory, 2941 Hobson Way, Wright-Patterson AFB, OH 45433, USA
(2) University of Dayton Research Institute, 300 College Park, Dayton, OH 45469, USA
(3) Mechanical, Aerospace, and Biomedical Engineering Department, University of Tennessee, 1512 Middle Dr, Knoxville, TN 37996, USA
(4) Cornell High Energy Synchrotron Source, 161 Synchrotron Drive, Ithaca, NY 14853, USA