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

Rhugdhrivya Rane,Akhilesh Kulkarni,Ankur Jain,Hardikkumar Prajapati,Victoria Chen,Robert Taylor

doi:10.3390/ma13020352

Abstract

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.

Highlights

Manufacturing techniques have constantly been evolving with a greater emphasis on fabricating complex geometries with a high degree of dimensional accuracy
2 2of techniques are a set of disruptive techniques that have gained popularity owing to their ease of availability, comparatively cheaper feedstock, and capability to build part geometries that would availability, comparatively cheaper feedstock, and capability to build part geometries that would otherwise be challenging to fabricate using traditional methods
The design of experiments (DOE) assumptions for the full factorial model are verified and the outcome of the analysis of variance (ANOVA) analysis is stated

Summary

Introduction

Manufacturing techniques have constantly been evolving with a greater emphasis on fabricating complex geometries with a high degree of dimensional accuracy. 2 2of techniques are a set of disruptive techniques that have gained popularity owing to their ease of availability, comparatively cheaper feedstock, and capability to build part geometries that would availability, comparatively cheaper feedstock, and capability to build part geometries that would otherwise be challenging to fabricate using traditional methods. Unlike traditional mold techniques, which involve complex designing and are time-consuming, AM uses digital technology manufacturing techniques, which involve complex designing and are time-consuming, AM uses to build parts [1]. The AM processes have been segregated into seven categories by the ASTM F42 digital technology to build parts [1]. These techniques differ from each other based on the by the ASTM F42 committee to standardize the terminology These techniques differ from each other type of feedstock used, the source of energy, and the method of material deposition. Fused filament based on the type of feedstock used, the source of energy, and the method of material deposition

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