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.