Browsing by Author "Russell, Timothy D., 1993-"
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Item Mechanical and thermal property prediction in single beads of large area additive manufactured short-fiber polymer composites.(2021-12-06) Russell, Timothy D., 1993-; Jack, David Abram, 1977-The prediction of mechanical and thermal properties of 3D printed short-fiber reinforced polymers (SFRPs) are investigated in this study. Methods are demonstrated for predicting the internal spatially varying fiber orientation state and resulting internal spatially varying stiffness, coefficient of thermal expansion, and strength properties in a single bead of 13% carbon fiber filled acrylonitrile butadiene styrene. The methods allow determination of both the spatially varying microstructural properties and the effective, bulk properties in any direction by finite element analysis. The focus of this work is specifically on Large Area Additive Manufacturing, an extrusion-based process for manufacturing thermoplastic parts that are several feet long, but the methods are applicable to other SFRP processing methods as well. For the experimental validation portion of this dissertation, a large-scale 3D printing system was constructed to fabricate test specimens. Tensile, compressive, and flexural specimens were fabricated with this system and tested. It is demonstrated that correct order of magnitude predictions can be made for the effective stiffness, CTE, and strength of LAAM-printed SFRP beads using the presented computational methodology. In addition, the computational methodology lays a framework that lends itself to improvement by using more accurate modeling inputs as they are measured, and more accurate underlying equations as they are developed.Item The effects of fiber orientation on stiffness and thermal expansion of large volume, anisotropic, short-fiber, composite material fabricated by Fused Filament Fabrication.(2017-09-14) Russell, Timothy D., 1993-; Jack, David Abram, 1977-Fused Filament Fabrication (FFF) is a rapidly improving 3D printing technology that can be used for manufacturing complex parts. The properties of these parts can be improved by adding short-fibers to the polymer feedstock. The fiber orientation state is critical to know in order to determine the final material properties though. This study investigates the reasonableness of several fiber orientation models based on their use in predicting the effective longitudinal Young’s modulus E_22 and CTE α_22 of a large volume, short-fiber composite, FFF printed bead. Comparisons are made between computational results from MATLAB (MathWorks, Inc., Natick, MA) and COMSOL Multiphysics (Stockholm, Sweden) to experimental results from samples collected from beads fabricated with an in-house, large scale bead deposition system. Based on comparisons of the computational and experimental results for E_22 and α_22, the Reduced Strain Closure (RSC) model [1] with 1/30≤κ≤1/5 seems to be the most reasonable.