PSI - Issue 51

Mohammed Algarni et al. / Procedia Structural Integrity 51 (2023) 185–191 M. Algarni/ Structural Integrity Procedia 00 (2022) 000–000

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for this technology increase is its low manufacturing requirements, requiring a proper 3D digital model without cutting, tempering, casting, and bending (Algarni (2021)). Hence, limited waste results. Additive manufacturing (AM) technologies have been heavily used to fabricate both complex-shaped and thin-walled parts. The first category of AM technologies involves creating the part by changing the states of the filament via a thermal process known as fusion disposition modeling (FDM). Then, selective laser sintering (SLS) (Beaman et al. (1997)) creates the parts by adhesive bonding of the material process known as laminated object manufacturing (LOM) (Feygin and Hsieh (1991)). The most used process is FDM, where a solid 3D model is saved in an STL file and printed in layers from bottom to top by a 3D FDM printer using different materials known as filaments (Algarni (2022)). The three well know filaments used in FDM are acrylonitrile butadiene styrene (ABS), poly-ether-ether-ketone (PEEK), and polylactic acid (PLA) all thermoplastics (Algarni and Ghazali (2021)). They are known for their strength, lightweight, formability, and relatively cheap cost. They are used in many medical, communications, and engineering applications. The manufactured parts’ mechanical and physical properties depend on the filament and FDM process parameters. Examples of the FDM process parameters are raster angle (RSA), air gap (ARG), infill density (IFD), printing time (PTT), extrusion temperature (EXT), and layer thickness (LYT). The material used in this research is PLA, where different process parameters were applied to achieve optimum mechanical properties. Many studies have been concerned with adjusting FDM process parameters through experimental and modeling methods to enhance printed parts properties based on their desired applications. Li et al. (2018) compared the different quantitative influences of LYT, PTT, and infill rate in past mechanical performance. They concluded that LYT and PTT played leading roles in the product bonding strength. A study by Zhou et al. (2018) performed an experimental investigation on the RSA and ARG influence on the ultimate tensile strength (UTS) and modulus of elasticity (E). Their results showed that decreasing the ARG leads to higher UTS. A more recent study by Pires et al. (2020) created a model based on statistically based experiment results to predict the mechanical behavior of the printed parts via varying the printing process parameters. Cojocaru et al. (2022) systematically investigated the effect of six process parameters on tensile and compression strength and bending stiffness. Their results showed that using a multidirectional raster angle on one part improved the mechanical properties compared to a unidirectional raster. Finally, a study by Bembenek et al. (2022) showed that the most influential FDM process parameter on the mechanical strength is the IFD. Our study investigates the influence of RSA, LYT, and IFD process parameters on a specimen’s tensile strength and strain behavior. The RSAs sets were 0º, 45º, and 90º, where 0º is directed parallel to the applied tensile force and 90º is directed perpendicular to tensile force. The LYT sets were 0.1, 0.2, and 0.3 mm; the IFD sets were 30%, 50%, and 80% of the specimens’ inner space. Experimental tests were run on all sets of process parameters, and models were created to describe the influence of the printing parameters on the tensile strength and strain behavior. Finally, a comparison of the modeling and experimental results was evaluated, and a set of optimized process parameters were suggested for higher strength and strain. 2. Experimental Process 2.1. Parts Fabrication by FDM The parts were made of PLA material and 3D printed by extrusion through a heated nozzle in layers using a Creality printer (model Ender-3) substrate. The specimens were designed based on ASTM D638-14 (Type IV) where the gauge length is 33.0mm and thickness is 4.0mm. 2.2. Process Parameters and Design of Experiment The experimental design was based on the number of process parameters and the specimens. The process parameters chosen were raster angle (RSA), layer thickness (LYT), and infill density (IFD). The RSA is the raster movement direction with respect to the loading direction. The RSAs selected were 0º, 45º, and 90º, where 0º is directed parallel to the applied tensile force and 90º is directed perpendicular to tensile force. The LYT is the thickness of the deposited material measured during the printing in millimeters. The selected LYTs were 0.1, 0.2, and 0.3 mm. Finally, the third process parameter is the IFD, which defines the percentage of material within the printed part. The selected