Improvement in build-direction thermal conductivity in extrusion-based polymer additive manufacturing through thermal annealing

Prajapati, Hardikkumar; Chalise, Divya; Ravoori, Darshan; Taylor, Robert M.; Jain, Ankur

doi:10.1016/j.addma.2019.01.004

Cited by 26 publications

(23 citation statements)

References 20 publications

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“…Moreover, the rigidity and charge of the polymer chains were not taken into consideration. Prajapati et al [ 27 ] proposed Arrhenius kinetics theory to model the thermal annealing of FFF parts. The theory relates the neck size growth with the exponent of activation energy, universal gas constant and the temperature at which the annealing is performed.…”

Section: Literature Reviewmentioning

confidence: 99%

The Effect of Annealing on Additive Manufactured ULTEM™ 9085 Mechanical Properties

Zhang

Moon

2021

Materials

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Fused filament fabrication (FFF) is increasingly adopted for direct manufacturing of end use parts in an aviation industry. However, the application of FFF technique is still restricted to manufacturing low criticality lightly loaded parts, due to poor mechanical performance. To alleviate the mechanical performance issue, thermal annealing process is frequently utilized. However, problems such as distortion issues and the need for jigs and fixtures limit the effectiveness of the thermal annealing process, especially for low volume complex FFF parts. In this research, a novel low temperature thermal annealing is proposed to address the limitations in conventional annealing. A modified orthogonal array design is applied to investigate the performance of ULTEM™ 9085 FFF coupons. Further, the coupons are annealed with specialized support structures, which are co-printed with the coupons during the manufacturing process. Once the annealing process is completed, multiscale characterizations are performed to identify the mechanical properties of the specimens. Geometrical measurement of post annealed specimens indicates an expansion in the layering direction, which indicates relief of thermal stresses. Moreover, annealed coupons show an improvement in tensile strength and reduction in strain concentration. Mesostructure and fracture surface analysis indicate an increase in ductility and enhanced coalescence. This research shows that the proposed annealing methodology can be applied to enhance the mechanical performance of FFF parts without significant distortion.

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Section: Literature Reviewmentioning

confidence: 99%

The Effect of Annealing on Additive Manufactured ULTEM™ 9085 Mechanical Properties

Zhang

Moon

2021

Materials

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“… There is also precedent for the employment of post-printing annealing to remove residual viscoelastic stresses and increase the final crystal fraction, thereby improving thermal [100] and mechanical properties (Fig. 6d, data adapted from Ref.…”

Section: Discussion and Future Directionsmentioning

confidence: 99%

Advances in modeling transport phenomena in material-extrusion additive manufacturing: Coupling momentum, heat, and mass transfer

2020

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Material-extrusion (MatEx) additive manufacturing involves layer-by-layer assembly of extruded material onto a printer bed and has found applications in rapid prototyping. Both material and machining limitations lead to poor mechanical properties of printed parts. Such problems may be addressed via an improved understanding of the complex transport processes and multiphysics associated with the MatEx process. Thereby, this review paper describes the current (last 5 years) state of the art modeling approaches based on momentum, heat and mass transfer that are employed in an effort to achieve this understanding. We describe how specific details regarding polymer chain orientation, viscoelastic behavior and crystallization are often neglected and demonstrate that there is a key need to couple the transport phenomena. Such a combined modeling approach can expand MatEx applicability to broader application space, thus we present prospective avenues to provide more comprehensive modeling and therefore new insights into enhancing MatEx performance.

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“…Previous studies have shown that applying thermal annealing alone leads to a substantial increase in the bond length at the interface, and in turn increases the thermal and mechanical properties of the parts [9,38]. The goal of the present study is to characterize and study the increase in ultimate tensile strength and develop a statistical model by subjecting the FFF parts to a post process thermal annealing, while simultaneously applying an initial static uniaxial load.…”

Section: Introductionmentioning

confidence: 98%

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

et al. 2020

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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.

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Improvement in build-direction thermal conductivity in extrusion-based polymer additive manufacturing through thermal annealing

Cited by 26 publications

References 20 publications

The Effect of Annealing on Additive Manufactured ULTEM™ 9085 Mechanical Properties

The Effect of Annealing on Additive Manufactured ULTEM™ 9085 Mechanical Properties

Advances in modeling transport phenomena in material-extrusion additive manufacturing: Coupling momentum, heat, and mass transfer

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

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