Introduction
Manufacturers in all industries are looking for lightweight materials to save money and material without sacrificing strength. To improve vehicle efficiency, the weight of automobile components must be reduced while maintaining an estimated strength. In additive manufacturing, materials will be added layer by layer, and components will be created. However, additive manufacturing saves material, reduces fabrication time, allows for the fabrication of complex geometry, and provides material flexibility. Automotive, aerospace, agriculture, fashion, medical, mechanical, and pharmaceutical industries use the additive manufacturing technology.[1, 2, 3].Parts printed by additive manufacturing are used as prototype models, for design verification, testing, and assembly verification in industrial and medical applications [4, 5]. AM techniques include stereo lithography, fused deposition modeling (FDM), selective laser sintering, and laminated object modeling,etc.. [6, 7, 8]. The development of new materials with the necessary properties contributes to the expansion of FDM processes and applications in various industries [11]. Several studies attempted to optimize the FDM process parameters (orientation and raster angle) to improve the properties of printed parts. [12]. The surface roughness can be reduced by 38 to 55 percent by controlling the road width and layer thickness [13]. The bonding of the materials between the layers influenced the anisotropy property as well as the fatigue strength and ultimate strength of the printed parts [14].
The composite filaments with single, double, and triple particle sizes, the mechanical properties such as tensile strength, young’s modulus, and so on are best achieved with double particle size (DPS) [15]. The square shape of the nozzle increased tensile strength while decreasing porosity by 7% due to reduced voidspace between the subsequent layers [16]. E-Glass fiber, Thermoplastic polyurethane elastomer, and PLA-loaded composite materials outperform injection molded composites. Because of the stiffening mechanism in 3D printed specimens, the tensile strength of the GF-reinforced models was reduced by 41% to 32% [17]. The PLA/Carbon Black and PLA/Graphene filament 3D printed structures showed no microstructural changes, but the filament resistivity was reduced 4-6 times compared to the printed parts due to the filament extrusion process. The resistivity of printed parts improved 1500 times for printed PLA/Graphene and 300 times for PLA/Carbon black due to void volume and expansion processes in thick layers [18]. By optimizing the process parameters, the Kevlar fiber (11.5%) by volume increases the compressive strength of lightweight composite materials. By increasing the density of the parts, the composite printed parts’ strengths are improved [19]. After annealing, the mechanical properties of the PLA/CF-produced parts did not improve the crystalline and ultimate strains were unaffected. However, the 15% fiber addition greatly enhanced the elastic modulus by up to 78%. The voids in the printed specimens were aligned with the extrusion line, and the annealing procedure marginally reduced the voids in consolidation [20]. The tensile modulus of the PLA/Carbon fiber (short) improved from 1.16 times to 2.2 times higher than PLA. Because of the fiber orientation in the printing direction, the manufactured parts improve stiffness along the printing path, whereas the printing direction is unaffected in PLA. Furthermore, the composite material decreased the failure strain rate and combining carbon fiber with PLA material enhanced the modulus of elasticity [21&22].
When the temperature rises from 200°C to 230°C, the continuous carbon fiber in PLA increases the bonding strength. [23]. In FDM part fabrication, using the PLA/CFRTPC, accommodates the fiber content up to 27% and increases the flexural strength and modulus of 335 MPa and 30 GPA. The extrusion pressure and overlap pressure bonding, improve the flexural strength when the federate is increased from 60-80 mm/min [24]. The agent methylene dichloride solution (8%) with the PLA improves composite bonding and increases the tensile strength by 13.8% and flexural strength by 164% over unprocessed PLA/CF composites [25]. The continuous carbon fiber printed parts with different densities (20% to 100%) improve the tensile strength by 70% and the flexural strength by 18.7% [26].
When up to 1.5% (by weight) of a 14-micron size wood floor is added to the PLA, the elastic modulus increases by up to 30%, and the tensile strength equals 66% of the compressive strength [27]. The 3D printing of fiber-reinforced materials has the greatest influence on the printing direction [28]. The addition of natural long bamboo fiber 100-300-micron size to PLA improves flexural strength linearly up to the addition of 70% bamboo fiber [29]. Continuous fiber impregnation, such as carbon fiber or twisted yarn, improves the strength of printed parts. The mechanical strength and tensile modulus of carbon fiber-reinforced 3D printed parts are increased by 435 and 599%, respectively [30]. The PLA/conductive graphene (10%) homogeneous dispersion improves mechanical and dynamic properties by 27% (from 31.6MPa to 40.2 MPa) and 30% (from 1.8 GPA to 2.45 GPA), respectively [31]. The PLA/Aramid composite filaments ensure that 3D printed parts are manufactured without difficulty, and fiber placement along the loading direction improves the mechanical properties of printed parts [32].
PLA/Ramie fibers significantly improve tensile, flexural, and impact strength, because of the fiber orientation along the loading direction [33]. The PLA/MWCNT (Multiwall Carbon NanoTube) improves the material property; up to 10% of the MWCNT disperses completely in the PLA [34]. 3D printed samples had lower yield strength and elongation at break than hot-pressed samples. The PLA/bronze composite increases the young’s modulus while decreasing elongation at break and yield strength by 33.5 percent and 7%, respectively. [35]. Also, by optimizing the machine parameters, considerable mechanical properties can be improved [36]. The raster angles influence the strength of 3D printed parts; changing the raster angle changes the properties of the printed parts [37]. The strength of the printed parts in the Z-axis direction is solely dependent on the bonding between the layers, the parts in the X-Y direction have a higher load-bearing capacity [38]. The printed parts exhibit greater dimensional stability and strength for the smallest layer thickness. The thinnest layer reduces the void space between the layers [39]. Raster patterns, raster angle, contour number, and dimensions all have a significant impact on the strength of printed parts [40].
The majority of research has focused on control parameters and the mechanical properties of FDM-fabricated objects. The machine parameters have little effect on the mechanical properties of FDM fabricated components, but the material used to fabricate the components has a significant impact on FDM. A number of researchers prepared the PLA-composite material, investigated its mechanical properties, and demonstrated significant improvement. However, very few studies have been conducted on the fabrication of PLA sandwiches using dual-extrusion FDM printers. The goal of this article is to investigate the tensile properties of sandwich structures made of PLA-PLA/Composite using FDM machines to control the machine parameters.