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Open AccessFeature PaperArticle

Post-Process Effects of Isothermal Annealing and Initially Applied Static Uniaxial Loading on the Ultimate Tensile Strength of Fused Filament Fabrication Parts

1
Mechanical and Aerospace Engineering, University of Texas at Arlington, Arlington, TX 76019, USA
2
Industrial, Manufacturing, & Systems Engineering, University of Texas at Arlington, Arlington, TX 76019, USA
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Author to whom correspondence should be addressed.
Materials 2020, 13(2), 352; https://doi.org/10.3390/ma13020352
Received: 13 September 2019 / Revised: 11 November 2019 / Accepted: 12 December 2019 / Published: 12 January 2020
(This article belongs to the Special Issue New Materials and Approaches in Polymer Additive Manufacturing)
Fused filament fabrication (FFF) is one of the most popular additive manufacturing (AM) techniques used to fabricate polymeric structures. However, these polymeric structures suffer from an inherent deficiency of weak inter-laminar tensile strength. Because of this weak inter-laminar strength, these parts fail prematurely and exhibit only a fraction of the mechanical properties of those fabricated using conventional means. In this paper, we study the effect of thermal annealing in the presence of an initially applied static uniaxial load on the ultimate tensile strength of parts fabricated using FFF. Tensile specimens or dogbones were fabricated from an acrylonitrile butadiene styrene (ABS) filament with a glass transition temperature (Tg) of 105 °C; these specimens were then isothermally annealed, post manufacture, in a fixture across a given range of temperatures and static loads. Tensile testing was then performed on these specimens to gauge the effect of the thermal annealing and static loading on inter-laminar tensile strength by measuring the ultimate tensile strength of the specimens. A design of experiments (DOE) approach was followed to calculate the main and interaction effects of the two factors (temperature and static loading) on the ultimate tensile strength, and an analysis of variance was conducted. Cross-sectional images of the specimens were studied to observe the changes in the mesostructure of the specimens that led to the increase in inter-laminar strength of the parts. The results show that temperature plays a dominant role in increasing the ultimate tensile strength and an 89% increase in the average ultimate tensile strength was seen corresponding to an annealing temperature of 160 °C. A change in the mesostructure of the parts is seen, which is characterized by an increase in bond length and void coalescence. These results can be helpful in studying the structural strength of 3D printed parts, and thus could eventually guide the fabrication of components with strength comparable to those of conventional manufacturing techniques. View Full-Text
Keywords: additive manufacturing; fused deposition modelling; interface healing; ultimate tensile strength; thermal annealing; uniaxial loading; post processing additive manufacturing; fused deposition modelling; interface healing; ultimate tensile strength; thermal annealing; uniaxial loading; post processing
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Rane, R.; Kulkarni, A.; Prajapati, H.; Taylor, R.; Jain, A.; Chen, V. Post-Process Effects of Isothermal Annealing and Initially Applied Static Uniaxial Loading on the Ultimate Tensile Strength of Fused Filament Fabrication Parts. Materials 2020, 13, 352.

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