Abstract: Additive manufacturing (AM) methods have greatly increased our ability to fabricate complex shapes and multi-material architectures. However, better materials are needed which compete with conventional engineering materials and fully leverage the unique capabilities of 3D printing. Specifically, lightweight 3D-printable polymer composite materials are of considerable interest, as are new composites which incorporate hierarchical design aspects observed in natural materials, for example, bone, nacre, and wood. This seminar will focus on recent efforts in the development and characterization of epoxy-based 3D-printable composites for use with direct-write robocasting. In this process, rheologically-tailored inks are deposited via filamentary extrusion through sub-millimeter nozzles to manufacture parts layer-by-layer. Because the shear and extensional flows in the nozzle induce alignment of high aspect ratio particles in the ink, highly efficient short fiber composites with exceptional properties can be printed. Furthermore, anisotropy can be tuned in these materials through choice of filler particle morphology, and orientation can be locally controlled within a component by tailoring the print path. Printed, short fiber polymer composites achieve Young’s modulus values of up to 24 GPa, up to 20x higher than commercially available printed polymers, while maintaining comparable tensile strength values (40-100 MPa). This talk will conclude with characterization of lightweight 3D-printed cellular structures and preliminary efforts towards synthetic brick-and-mortar composites, as well as future directions for achieving these and other advanced architectures in engineering materials systems. Bio: Brett is currently a staff scientist in additive manufacturing at Oak Ridge National Laboratory, where he is working on in situ thermal imaging of metal and polymer AM processes, thermo-mechanical modeling of the polymer composite deposition process to reduce component warping and delamination, and developing new capabilities at the lab for multi-material printing of ceramic-metal composites with controlled architecture. Brett came to the lab following a position as a Postdoctoral Research Fellow in the Lewis Group at the Harvard School of Engineering and Applied Sciences and the Wyss Institute for Biologically Inspired Engineering, where his work focused on developing thermoset inks for 3D printing of polymer composites inspired by balsa wood. Brett received his Ph.D. in Materials from the University of California, Santa Barbara, and his B.S. in Mechanical Engineering from the University of Kentucky. It was while attending evening pottery classes in the art department at UK that Brett developed his deep interest in ceramics, and decided to pursue further studies in materials. Research interests include ceramic-metal composites, advanced processing and manufacturing techniques, and the effects of material orientation, length scales, and topology in architectured composites and structures. Host: Prof. Megan Valentine/Prof. Matthew Begley