No abstract

Additive Manufacturing (AM) is gaining enormous attention from academic and industrial sectors for product development using different materials. Fused Deposition Modelling (FDM) is a popular AM method that works with thermoplastics. This process offers benefits of customisation both in terms of hardware and software in the case of desktop-based FDM systems. Enhancement of mechanical properties for the traditional thermoplastic material is a widely researched area and various materials have been added to achieve this goal. This paper focuses on the manufacture of glass fiber reinforced plastic (GFRP) composites using Hybrid Fused Deposition Modelling (HFDM). Commonly available polylactic acid or polylactide (PLA) material was inter-laced with 0.03 mm thick glass fiber sheets to manufacture GFRP products followed by tensile testing. This was done to investigate whether adding more layers increases the tensile strength of the GFRP products or not. Furthermore, the maximum number of glass fiber layers that can be added to the 4 mm thick specimen was also identified. This was done to demonstrate that there is an optimal number of glass fiber layers that can be added as after this optimal number, the tensile strength start to deteriorate. Microstructural analysis was undertaken after tensile testing followed by ultrasonic testing to assess the uniformity of the GFRP composites.

Fused filament fabrication (FFF) is one of the most widely used additive manufacturing processes in the market. It is based on material extrusion and utilises thermoplastic materials to manufacture bespoke products. The process is extremely popular due to its ease of operation and variety of available materials. To enhance the mechanical performance of parts made by FFF, reinforcements including nanoparticles, short or continuous fibers and other additives have been added to commonly used thermoplastics such as acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA). Such new materials require optimization of process parameters to achieve the desired results. One such parameter is the material extrusion rate that can result in under or over extrusion leading to a variety of applications. In this study, PLA and HDPlas® PLA-GNP-A (PLA reinforced with functionalized graphene nanoplatelets) have been used to investigate the effects of material extrusion rate. An extensive comparative analysis has been provided where parts have been manufactured using a desktop 3D printer with the two materials at four extrusion temperatures (180 °C, 190 °C, 200 °C and 210 °C) and ten different extrusion rates (ranging from 70% to 160%). The study aims to evaluate the effects of extrusion temperatures and material extrusion rates on mass, dimensional accuracy, surface texture and mechanical properties of the two materials. Microstructural analysis has also been carried out to evaluate the surfaces of parts after manufacture as well as their fractured surfaces after mechanical testing to determine the impact of extrusion rate on failure modes. The results have shown that the graphene reinforced PLA material is affected more adversely by changes in material extrusion rate compared to PLA. This work provides a good comparison between two materials manufactured at four different extrusion temperatures and how the material extrusion rate can be leveraged to achieve optimal surface finish and mechanical strength.

Ironing is a useful feature for parts made by fused filament fabrication (FFF), as it can smooth out surfaces using heat and extruding a small amount of material. Like any other processing parameter for FFF, ironing also requires optimisation to ensure a smooth surface can be achieved with limited adverse effects on the other features of the printed part. Even with such a beneficial use case, ironing is still considered experimental and, therefore, this study aims to investigate its effects on dimensional accuracy, surface roughness, and the hardness of two commonly used amorphous thermoplastics, i.e., ABS (acrylonitrile butadiene styrene) and ASA (acrylonitrile styrene acrylate). An extensive comparative analysis has been provided where parts have been manufactured using a low-cost, desktop-based 3D printer, with the two materials at three different ironing line spacings (0.1 mm, 0.2 mm, 0.3 mm), three different ironing flows (10%, 20%, 30%), and three different ironing speeds (50 mm/s, 100 mm/s, 150 mm/s). The study focuses on evaluating the effects of these different ironing parameters and determining the optimal combination for bespoke product requirements. The results showed that ASA was more adversely affected by the changes in ironing parameters compared to ABS. However, the different ironing parameters were proven to improve the smoothness as well as hardness of the parts, compared to the un-ironed samples of ABS and ASA. This work provides a good comparison between two popular amorphous materials and offers ways to leverage ironing parameters to achieve dimensional accuracy, optimal surface finish, and better hardness values.

The significance of non-destructive testing (NDT) methods cannot be overstated as they help to evaluate the properties of a material without damaging/fracturing it. However, their applicability is dependent on their ability to provide reliable correlation with destructive tests such as tensile and flexural. This correlation becomes more problematic when the material is not homogeneous, such is the case with parts manufactured using a popular additive manufacturing process termed as fused filament fabrication (FFF). This process also requires optimisation of its parameters to achieve desired results. Therefore, this study aims to investigate the effects of four different nozzle temperatures, print bed temperatures, and print speeds on FFF-printed Haydale’s Synergy Graphene Enhanced Super Tough PLA through three non-destructive (ultrasonic, hardness, strain) and two destructive (tensile, flexural) testing methods. Samples were manufactured using Anet® ET4 Pro 3D printer and evaluated as per British and International standards. Two non-destructive tests, i.e., ultrasonic and hardness have been associated with evaluating the tensile properties of the manufactured parts. These results were correlated with destructive tensile testing and showed good agreement. The NDT method of strain measurement showed a very good correlation with the destructive three-point flexural test and was able to provide a reliable evaluation of flexural properties as a function of all three processing parameters. The results presented in this work highlight the importance of NDT methods and how they can be used to evaluate different properties of a material.