Investigating the Effects of Annealing on the Mechanical Properties of FFF-Printed Thermoplastics

Javaid Butt,Raghunath Bhaskar

doi:10.3390/jmmp4020038

Javaid Butt, Raghunath Bhaskar

Open Access

https://doi.org/10.3390/jmmp4020038

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Abstract

Fused filament fabrication (FFF) is a cost-effective additive manufacturing method that makes use of thermoplastics to produce customised products. However, there are several limitations associated with FFF that are adversely affecting its growth including variety of materials, rough surface finish and poor mechanical properties. This has resulted in the development of metal-infused thermoplastics that can provide better properties. Furthermore, FFF-printed parts can be subjected to post-processes to improve their surface finish and mechanical properties. This work takes into consideration two commonly used polymeric materials, i.e., ABS (acrylonitrile butadiene styrene) and PLA (polylactic acid) and compares the results with two metal-infused thermoplastics i.e., copper-enhanced PLA and aluminium-enhanced ASA (acrylonitrile styrene acrylate). The four different materials were subjected to a post-process called annealing to enhance their mechanical properties. The effect of annealing on these four materials was investigated through dimensional analysis, ultrasonic testing, tensile testing, microstructural analysis and hardness testing. The results showed that annealing affects the materials differently. However, a correlation among ultrasonic testing, tensile testing and microstructural analysis was observed for all the materials based on their crystallinity. It was found that the semi-crystalline materials (i.e., PLA and copper enhanced PLA) showed a considerable increase in tensile strength post-annealing. However, the amorphous materials (ABS and aluminium-enhanced ASA) showed a comparatively lower increase in tensile strength, demonstrating that they were less receptive to annealing. These results were supported by higher transmission times and a high percentage of voids in the amorphous materials. The highest hardness values were observed for the ASA material and the lowest for the ABS material. This work provides a good comparison for the metal-infused thermoplastics and their applicability with the commonly used PLA and ABS materials.

Highlights

The production of customised products at low costs and required mechanical properties is in demand as it leads to higher customer satisfaction and profits for manufacturers
In addition to these materials, the manufacture of composites using fused filament fabrication (FFF) has been widely researched due to the ease of modifications in software and hardware for FFF systems [4,5,6]. These efforts have resulted in the development of functional electronics [7,8] and composites with superior mechanical properties [9,10]. This has led to the development of metal-infused filaments for FFF that can provide the aesthetics and a relative increase in mechanical properties compared to conventional FFF materials
These examples show the need for optimization of process parameters to achieve high quality products from FFF. This is why the use of experimental approaches and predictive techniques is becoming exceedingly prevalent to characterize the mechanical properties of FFF-printed parts [24]. Considering this discussion, this paper aims to provide a comparative account of metal-infused thermoplastics and their applicability with widely used PLA and ABS materials

Summary

Introduction

The production of customised products at low costs and required mechanical properties is in demand as it leads to higher customer satisfaction and profits for manufacturers. There are seven main categories of AM; vat photopolymerization, powder bed fusion, binder jetting, material jetting, sheet lamination, material extrusion and directed energy deposition [1,2,3] These technologies can work with different materials (e.g., metals, polymers, ceramics) to manufacture customised products. In the form of filaments, are heated and extruded out of a nozzle onto a build plate to manufacture a product Different materials such as PLA (polylactic acid), ABS (acrylonitrile butadiene styrene), ASA (acrylonitrile styrene acrylate), PEEK (polyether ether ketone), nylon, PET (polyethylene terephthalate) and ultem can be used with FFF. ASA is gradually gaining attention due to its superior properties for composite production using FFF [13]

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