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  1. null (Ed.)
  2. null (Ed.)
    Pressure distributions within a single screw extruder are dependent on several factors, namely, processing parameters and flow geometry. The Big Area Additive Manufacturing (BAAM) system involves a complex flow geometry with multiple flow zones following the screw extruder. This study utilized experimental data and a one-dimensional (1-D) analytical model to compare pressures at specific areas of interest in the BAAM system. Initial results show a need for further two-dimensional (2-D) and three-dimensional (3-D) simulation and modeling of the BAAM extruder with more accurate underlying assumptions. The results of this work will allow for further study of BAAM input parameters for optimal print quality, material properties, and print head geometric design. 
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  3. null (Ed.)
    Carbon fiber (CF)-reinforced thermoplastic composites have been widely used in different structural applications due to their superior thermal and mechanical properties. The big area additive manufacturing (BAAM) system, developed at Oak Ridge National Laboratory’s Manufacturing Demonstration Facility, has been used to manufacture several composite components, demonstration vehicles, molds, and dies. These components have been designed and fabricated using various CF-reinforced thermoplastics. In this study, the dynamic rheological and mechanical properties of a material commonly used in additive manufacturing, 20 wt% CF-acrylonitrile butadiene styrene (ABS), as well as three CF-reinforced high-temperature polymers, 25 wt% CF-polyphenylsulfone (PPSU), 35 wt% CF-polyethersulfone (PES), and 40 wt% CF-polyphenylene sulfide (PPS), used to print molds were investigated. The viscoelastic properties, namely storage modulus, loss modulus, tan delta, and complex viscosity, of these composites were studied, and the rheological behavior was related to the BAAM extrusion and bead formation process. The results showed 20 wt% CF-ABS and 40 wt% CF-PPS to display a more dominant elastic component at all frequencies tested while 25 wt% CF-PPSU and 35 wt% CF-PES have a more dominant viscous component. This viscoelastic behavior is then used to inform the deposition and bead formation process during extrusion on the BAAM system. 
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