Summary:
Together with our collaborator, Dr. Mehran Tehrani, we have established a reactive extrusion AM (REAM) system that is capable of fabricating parts from two-part thermoset resin systems with deposition rates that are 100x faster than typical desktop systems. The resulting parts display nearly isotropic properties, and the process is especially well-suited to fabricating functionally graded, composite parts because the liquid precursors are mixed on-demand. From a design perspective, this technology enables the design and fabrication of smart devices that are capable of actively changing shape as requirements change. We are working with collaborators at Penn State to design, fabricate, test, and model these devices.
Other process innovation research includes the establishment of a high-viscosity, large area stereolithography system, in collaboration with Dr. Rich Crawford and LLNL. The system is capable of printing with very high viscosity resins that yield tougher, stronger parts with bounding dimensions as large as 0.5 m. This effort has already led to two provisional patents. From an engineering design perspective, this capability is expected to lead to significant advances in our ability to design and fabricate soft robotics and deployable structures.
A third area of process innovation is volumetric powder bed fusion. Together with Dr. John Pearce, Dr. Joe Beaman, and collaborators at the University of Nottingham, Dr. Seeperad and her students are establishing a novel AM process in which RF radiation is used to fuse thermoplastic powders volumetrically in selective regions that are doped with conductive graphite. The process poses significant design challenges because the presence of dopants distorts the RF electromagnetic field, inducing hot and cold spots. As a result, an intended part geometry cannot be uniformly doped with conductive graphite; the graphite dopant must be functionally graded to re-distort the field and induce more uniform heating and fusing. Additional experiments are underway to refine this process and improve its speed along with the geometric accuracy and mechanical properties of resulting parts.
Collaborators:
UT Austin: Mehran Tehrani, Richard Crawford, John Pearce, Joe Beaman
Penn State: Mary Frecker, Zoubeida Ounaies
U Nottingham: Chris Tuck, Richard Hague, Ali Sohaib
Funding:
NSF, ExxonMobil, Lawrence Livermore National Laboratory
Related Publications:
Reactive Extrusion Additive Manufacturing (REAM)
Uitz, O., P. Koirala, M. Tehrani, C.C. Seepersad, 2021, “Fast, Low-Energy Additive Manufacturing of Isotropic Parts via Reactive Extrusion,” Additive Manufacturing, Vol. 41, pp. 1-12.
Koirala, P., O.L. Uitz, A.A. Oridate, C.C. Seepersad, and M. Tehrani, 2021, “Reactive Extrusion Additive Manufacturing of a Short Fiber Reinforced Thermoset Composite,” 36th Technical Conference of the American Society of Composites.
Leng, R., O. Uitz, Z. Ounaies, C. Seepersad, 2021, “Design and Characterization of a Multilayered Multifield-Actuated Polymer Unimorph,” ASME Conference on Smart Materials, Adaptive Structures, and Intelligent Systems, Paper No: SMASIS2021-68238.
High Viscosity Paste Stereolithography
Song, H., N.A. Rodriguez, C. C. Seepersad, R.H. Crawford, M. Chen, E.B. Duoss, 2021, “Development of a Variable Tensioning System to Reduce Separation Force in Large Scale Stereolithography,” Additive Manufacturing, Vol. 38, pp. 101816 (15 pages).
Volumetric Powder Bed Fusion
Allison, J., J. Pearce, J. Beaman, C.C. Seepersad, 2022, “Volumetric Fusion of Graphite-Doped Nylon 12 Powder with Radio Frequency Radiation,” Rapid Prototyping Journal, in press.