Content uploaded by Hisham Abusalma
Author content
All content in this area was uploaded by Hisham Abusalma on Feb 06, 2023
Content may be subject to copyright.
Content uploaded by Vukica Jovanovic
Author content
All content in this area was uploaded by Vukica Jovanovic on Jul 17, 2022
Content may be subject to copyright.
Content uploaded by Mohammad Sepahi
Author content
All content in this area was uploaded by Mohammad Sepahi on Oct 22, 2022
Content may be subject to copyright.
Mechanical Properties of 3D-Printed Parts Made
of Polyethylene Terephthalate Glycol
Mohammad Taregh Sepahi, Hisham Abusalma, Vukica Jovanovic, and Hamid Eisazadeh
Submitted: 18 December 2020 / Revised: 20 May 2021 / Accepted: 2 July 2021 / Published online: 19 July 2021
Fused deposition modeling (FDM), one of various additive manufacturing (AM) technologies, has revolu-
tionized the manufacturing industry, from the development of concept models to the creation of functional
parts. FDM uses a wide variety of materials to create 3D-printed parts. However, most FDM printers in the
market use polylactic acid (PLA) and acrylonitrile butadiene styrene (ABS) thermoplastic materials for
their good mechanical properties and low cost. Polyethylene terephthalate glycol (PETG) has recently
gained considerable attention due to its enhanced properties. Despite the potential attraction of PETG in
the 3D printing industry, very few studies have investigated its mechanical properties, such as toughness,
tensile strength, elongation at break, yield strength, and tensile modulus, which would then lead to the
development of more reliable standards for testing and inspection. In this paper, the mechanical properties
of PETG, as well as the mechanical properties of two popular FDM materials, PLA and ABS, are inves-
tigated and compared. A total of 75 tensile tests were carried out in order to investigate the effect of five
different raster angle directions on mechanical properties. Adequate strength and high ductility were
observed in PETG. Despite the ductility enhancement, PETG materials exhibited slight brittleness in tensile
test results and scanning electron microscope analysis, which could be attributed to raster angle. According
to the outcome of this investigation, recommendations for 3D printing of PETG material to fit the design
and application will be provided. This can result in more accurate reference data for potential applications
of these manufacturing technologies, as well as improved part and product quality.
Keywords 3D printing, ABS, additive manufacturing,
mechanical testing, PLA, polyethylene terephthalate
glycol (PETG)
1. Introduction
The FDM additive manufacturing process uses a wide
variety of materials to manufacture 3D-printed parts. The
material choice depends on the desired mechanical properties of
products, such as strength, toughness, stiffness, and the build
envelope of the additive manufacturing equipment. Some
reasons that materials with high toughness are used to create
specific parts are impact resistant and high durability. Other
applications may have a spotlight on more specific material
properties, such as melting point (Ref 1), coefficient of thermal
expansion (Ref 2), viscosity and layer adhesion (Ref 3), which
are crucial for the ease of material printability. All of these
parameters and their effects on the additive manufacturing
process must be better understood in order to apply the correct
build orientation and slicing settings (Ref 4) to the code that
controls the printer and to obtain the desired mechanical
properties for the part. As such (Ref 5), various materials are
currently available on the market for the FDM process.
Polylactic acid (PLA) and acrylonitrile butadiene styrene
(ABS) are some of the commonly used materials based on
the open literature. PLA is made from environmentally friendly
materials like fermented plant starch from corn, cassava,
sugarcane or sugar beet pulp. Some of its characteristics include
ease of printing due to its relatively low melting point, high
stiffness, and strength (Ref 1,3). As well, due to the lower
negative impact on human health, it is widely used for additive
manufacturing training since organic vapors emitted during the
process of heating thermoplastics differ among different
thermoplastic materials (Ref 6). On the other hand, ABS is
relatively strong, stiff, durable (Ref 7), and does not deform
over time (Ref 8) in service loading conditions, but it is
hazardous and toxic to humans. Polyethylene terephthalate
glycol (PETG), a copolyester-based polymer (Ref 9), which is
derived from polyethylene terephthalate (PET), has recently
gained considerable attention due to its promising potential in
FDM manufacturing. It contains added glycol, and unlike PET,
it does not exhibit strain-induced crystallization (Ref 10). The
application of PETG is well established through medical
industries, food applications, electronics, etc., due to its high
toughness, transparency, and chemical resistance (Ref 9,11).
Material selection is not the only design choice in the FDM
process (Ref 12). Process parameters, such as orientations of
the build, thermal conditions, and slicing parameters, are just as
important because they can influence the mechanical perfor-
Mohammad Taregh Sepahi and Hisham Abusalma are contributed
equally.
This invited article is part of a special topical focus in the Journal of
Materials Engineering and Performance on Additive Manufacturing.
The issue was organized by Dr. William Frazier, Pilgrim Consulting,
LLC; Mr. Rick Russell, NASA; Dr. Yan Lu, NIST; Dr. Brandon D.
Ribic, America Makes; and Caroline Vail, NSWC Carderock.
Mohammad Taregh Sepahi and Hisham Abusalma, Mechanical and
Aerospace Engineering Department, Old Dominion University,
Norfolk, VA 23518; and Vukica Jovanovic and Hamid Eisazadeh,
Engineering Technology Department, Old Dominion University,
Norfolk, VA 23518. Contact e-mail: heisazad@odu.edu.
JMEPEG (2021) 30:6851–6861 ÓASM International
https://doi.org/10.1007/s11665-021-06032-4 1059-9495/$19.00
Journal of Materials Engineering and Performance Volume 30(9) September 2021—6851
mance of the final FDM parts. Common building orientations,
how the part is positioned when produced (Ref 13), are
horizontal, vertical, and lateral, but other desired orientations,
such as inclined, may be used as well. Thermal conditions like
bed, extrusion, and ambient temperatures play an important role
in the shrinkage of the parts and adhesion with the previously
deposited layers.
The effect of these process parameters on the mechanical
properties were investigated in the literature. It was shown that
strength in the build direction is the weakest compared to other
directions (Ref 14,15). Also, the reduction of the layer
thickness increases tensile strength, but reduces the ductility
(Ref 16-18). It was demonstrated that a higher percentage of
infill density improves part strength by lowering the partÕs build
rate and increasing cost, although it increases the overall print
time. Therefore, a tradeoff among these factors should be
determined (Ref 17-20). Studies on the effect of raster angle on
mechanical properties of FDM parts showed a higher strain can
be obtained in the direction of the fiber, yet a lower strain in the
transverse direction (Ref 20). Recently, the effect of natural
fibers as reinforcement was also explored. It was shown that
high elasticity properties can be achieved in fiber direction
rather than transverse direction (Ref 21). Mechanical anisotropy
in FDM 3D-printed parts, which is an inherent nature of all AM
methods, is almost unavoidable due to the presence of voids in
the final printed parts’ structure (see) (Ref 4,5). However, the
voids can be minimized through process parameters and may
take different shapes accordingly. For instance, the thermal
conditions, such as previously deposited layer temperature and
extrusion temperature, are crucial in determining the bonding
quality between layers (Ref 8). Based on printing conditions,
three common voids are normally observed in the FDM parts,
which are demonstrated in a–c. If there is a small bonding area,
for instance, as seen in a, the lack of molecular diffusion of
polymer chains leads to weak bonding between the layers. As
the bonding area increases, the neck grows between adjacent
filaments, for instance, as seen in b and 1c. This causes the
polymer chains to diffuse to one another and increase
randomization of polymer chains across the filamentsÕinterface,
which subsequently provides stronger adhesion (Ref 8).
The FDM process parameters like raster angle, raster gap,
build orientation, layer thickness, and infill density affect
interlayer adhesion, microstructure, and, subsequently, mechan-
ical properties of the printed part. For instance, a thinner layer
increases necking between the adjacent layers, reducing void,
or the gap size, between the rasters. This improves the inter-
raster fusion bond (Ref 22). The inter-raster fusion bond failure
is the main contributor to failure of samples printed in 45°and
90°raster orientations (Ref 23). Longitudinal raster angle,
raster parallel with load direction or 0°raster orientation,
significantly increases the strength of the part because the
failure mode in such specimens is mostly trans-raster failure
because the weakest areas in the part with 0°raster orienta-
tion are the bonding between the layers (Ref 22). Additionally,
certain raster orientations lead to stress concentration in specific
loading modes, such as bending and torsion (Ref 24).
In general, there are two main mechanisms for absorbing
energy in polymers: crazing and shear yielding. According to
the SEM micrographs, when crazing occurs, small cracks are
formed, normal to the applied loading direction, which are then
bridged by many micro-fibrils. The crazes cause the polymer to
turn white (in the SEM images) when deformed due to the
scattering of light by these fibrils. Necking, on the other hand,
results in no stress whitening (Ref 25).
This study focuses on the general mechanical properties of
3D-printed PETG parts. The investigation into the failure
mechanism has higher credibility when it is compared with
those obtained from other materials in the same manufacturing
conditions. As such, the mechanical properties of PETG, along
with the most commonly used materials in the FDM market,
such as polylactic acid (PLA) and acrylonitrile butadiene
styrene (ABS) thermoplastics, are examined in the same test
and print environment; then the results are compared. Accord-
ing to the outcome of this investigation, observations related to
the various modes of 3D printing of PETG material will then be
investigated so that further applications of such materials in 3D
can be better understood for future applications in additive
manufacturing and part quality testing and inspection.
2. Printing Procedure
In this study, samples were prepared in accordance with the
ASTM D618 standards (Ref 26). This standard defines
humidity and temperature as parameters that influence test
results (Ref 26). As such, all materials were dried and kept
under control prior, during, and after the printing, according to
the test requirements. The geometry of the test samples was
chosen from the ASTM D618 standard (Ref 26). The standard
had multiple geometries to choose from. Types I, II, and III
were too large, which caused warping and thermal deformation
during the printing process in the longitudinal direction. Type V
was smaller than the tensile testing machine minimum dimen-
sions. Type IV geometry had neither of those issues and was
selected for testing the material.
The printing process was carried out after drawing the
sample geometry using SolidWorks CAD software. Designed
geometry was exported as an STL file and loaded into the
Ultimaker Cura software (Ref 27). The pre-printing process
was optimized using slicing features within the software to
Fig. 1. Three common voids observed in the FDM parts
6852—Volume 30(9) September 2021 Journal of Materials Engineering and Performance
ensure the raster angles were as desired. Ultimaker 3 Extended
3D printer was used to print the specimens. Before the printing
process, standard office glue was added on top of the printing
base plate to improve adhesion to the surface and prevent
warping (Ref 27). This step was recommended by the
Ultimaker user guide. Every test sample was printed individ-
ually after the base plate cooled down to room temperature to
ensure that the sample detached from the plate. Rafts and brims
are extra material printed around the base of the sample to
ensure adhesion to the surface. However, they were not used
because the printed sample had enough surface area to adhere
to the base plate. All three materials were printed in five distinct
angles: 0°,90°, 0/90°,45°and 45/135°, as depicted in Figure 2.
To assure repeatability of this study, five samples of each raster
angle were printed, resulting in a total of 75 samples. Figure 3
illustrates the build direction relative to specimen and build
platform. A summary of process parameters is shown in
Table 1, indicating 100 percent of infill density for all
specimens.
2.1 Tensile Testing
After printing, the specimens were removed from the print
bed, post processed, and measured by digital caliper to make
sure to comply with ASTM D618 standards (Ref 26). Testing
was carried out by an Alliance RF/300 testing machine that is
fitted with serrated-jaw tensile grips. The specimens were fitted
into the tensile jaws, checked for alignment, and then
pretensioned to eliminate compressive forces and improve
repeatability of the results. The test speed was set to 55 mm/s.
Following each test, the tensile test data were collected and
recorded for further analysis. Figure 4represents the fractured
specimen after the tensile test (Table 2).
2.2 Scanning Electron Microscope (SEM)
Scanning electron microscopy (SEM) characterization was
performed using a ‘‘Phenom Pure SEM Desktop’’ electron
microscope at Old Dominion University. Scanning was per-
formed in high vacuum mode at 5 kV acceleration voltage and
60 Pa vacuum. For the current magnification, no sample
coating was required, and the samples were only attached to the
mount with carbon conductive tapes. PLA, ABS, and PETG
plastic materials were conductive enough for low magnification
SEM imaging without applying any gold or carbon coating.
The failed samples were carefully cut with a sharp blade and
Fig. 2. Schematic of five raster angles and dimension of tensile test specimens used in this study. (a) 0°, (b) 90°, (c) 0/90°, (d) 45°, (e) 45/135°
Fig. 3. Printed orientation relative to the gravity vector or build
direction
Table 1. Printing parameters of the specimens
PETG ABS PLA
Deposition temp 240 °C 230 °C 200 °C
Deposition speed 55 mm/s 55 mm/s 70 mm/s
Bed temp 70 °C80°C60°C
Layer thickness 0.1 mm 0.1 mm 0.1 mm
Number of contours 1 1 1
Infill density 100% 100% 100%
Fan speed 50% 5% 100%
Journal of Materials Engineering and Performance Volume 30(9) September 2021—6853
Fig. 4. Fractured specimen after tensile test. (a) PETG, (b) PLA, (c) ABS
Table 2 Summary of tensile tests break for various print orientations of ABS, PETG and PLA materials
Sample
strength
MPa
Std
deviation
Yield
strength
Std
deviation
Average strain
at break
Std
deviation
Ultimate
toughness
Std
deviation
Tensile
modulus
Std
deviation
CPE 0 49,37 0,38 5,31 0,27 122,46 16,58 4251,56 402,44 1468,26 31,44
CPE 90 35,86 6,34 4,96 0,11 3,03 0,71 77,10 12,71 1387,23 33,93
CPE 45 37,37 5,94 4,92 0,13 3,62 0,21 116,54 16,68 1381,90 68,97
CPE 0/
90
46,47 3,67 5,46 0,22 4,29 0,66 152,18 11,00 1452,67 74,72
CPE
45/-
45
40,95 1,04 4,44 0,50 4,39 0,27 125,32 12,26 1354,82 32,47
ABS 0 38,75 1,91 4,87 0,12 4,16 1,47 202,68 12,24 1527,29 43,15
ABS 90 32,27 1,23 4,56 0,15 2,44 0,30 44,60 7,61 1479,40 28,45
ABS 45 36,68 0,90 4,71 0,13 3,05 0,17 70,26 4,16 1479,97 22,96
ABS 0/
90
33,65 1,13 3,90 0,11 2,90 0,14 59,12 5,60 1462,99 12,28
ABS
45/-
45
37,09 0,90 4,46 0,19 3,37 0,21 109,24 6,76 1475,83 30,24
PLA 0 59,98 5,16 8,16 0,33 3,04 0,27 123,80 16,16 2462,27 163,8
PLA 90 51,57 1,02 6,40 0,28 2,77 0,09 93,76 7,26 2510,50 39,73
PLA 45 59,02 1,43 6,34 0,18 3,24 0,11 221,79 15,21 2487,24 61,82
PLA 0/
90
57,22 0,84 7,01 0,19 2,93 0,10 108,41 13,22 2567,41 112,18
PLA
45-45
60,81 0,31 7,01 0,22 3,28 0,13 291,84 64,54 2514,88 55,47
Fig. 5. Results of tensile tests, 0°raster angle
Fig. 6. Results of tensile tests, 90°raster angle
6854—Volume 30(9) September 2021 Journal of Materials Engineering and Performance
then cleaned with air pressure to remove dust and any foreign
particles. Then, the prepared samples were loaded into the SEM
machine. Several micrograph images were captured from the
fracture surfaces at various zoom levels.
3. Results
Printing material and raster angle were the factors that
changed during this experiment.
3.1 Sample Comparisons
PLA samples were selected as the reference for all raster
angle comparisons. PLA demonstrated higher tensile strength
and reasonable toughness when compared to similar raster
angles in PETG and ABS. The tensile test results achieved for
three materials are presented in Figs. 5,6,7,8and 9.
Figure 5shows that PLA undergoes little elongation (brittle
like) after reaching its yielding point with 0 raster orientation.
On the other hand, ABS and PETG show ductile and rubber-
like behaviors, respectively. PLA has the highest strength of all
three materials with about 60 MPa, while PETG has an ultimate
strength of 45 MPa and ABS has 35 MPa of strength. PETG
has very high elongation with 140% strain at break. Figure 6
shows the stress strain curves of 90 raster angle samples in
which the highest strength belongs to the PLA sample. PETG
has the largest elongation. Interestingly, the strength of PETG is
higher than that of ABS. ABS has a slightly higher stiffness
compared to PETG. Figure 7shows the stress strain curves of
0/90 raster angle samples. The trends are similar to those
demonstrated in Figure 6with the difference being that PETG
shows higher stiffness than ABS. Figure 8illustrates the stress
strain behavior of samples with 45 raster orientation, in which a
new behavior is observed, especially for PLA. PLA was
relatively ductile and revealed the highest strength. This is
unlike the other raster directions, where PETG experienced the
highest elongation. Figure 9shows the stress strain curves of
45/135 raster angles samples. This result is similar to Figure 8
where PLA has an improved ductility. However, PETG has
higher elongation in this case. ABS is inferior to PETG in most
mechanical properties.
The quantitatively mechanical properties were extracted
from stress–strain curves and classified into five sections:
elongation at break, ultimate toughness, yield strength, ultimate
strength, and tensile modulus, which are further investigated
using SEM micrographs.
3.2 Elongation at Break
Figure 10a demonstrates the summary of elongation at
break. Overall, PETG exhibited the maximum elongation at
break among the tested materials. PLA and ABS displayed
similar elongation at break except at 45°raster angle, where
PLA showed a higher elongation at break compared to other
materials in this (45°) raster angle. Most specimens reached
their maximum elongation at break at 0°raster angle, and the
minimum elongation at break was observed to be at 90°raster
angle. PETG 0°exhibited a considerably higher elongation at
break, with an average elongation at break of 122.5% with a
standard deviation of 16.9%. In contrast, the majority of PLA
and ABS exhibited a brittle behavior, where ABS 0°displayed
an average elongation of 12% at break.
The 45°and 45/135°raster angles tend to be favorable for
PLA compared to ABS and PETG. These raster angles also
exhibited the highest mechanical properties for PLA. These
results are elaborated on in more detail in the discussion section.
At an angle of 90°, all specimens displayed a brittle
behavior. Hence, this raster angle exhibited the lowest amount
Fig. 7. Results of tensile tests, 0/90°raster angle
Fig. 8. Results of tensile tests, 45°raster angle
Fig. 9. Results of tensile tests, 45/135°raster angle
Journal of Materials Engineering and Performance Volume 30(9) September 2021—6855
of elongation relative to the other raster angles. The 45/135°
raster angle has the second highest elongation at break for the
PETG and ABS specimens. In addition, this angle can provide
a high amount of elongation, in some cases, compared to other
raster angles (e.g., PLA 45/135°).
3.3 Ultimate Toughness
Ultimate toughness, or total energy, is defined as the amount
of absorbed energy prior to fracture (Ref 28). Ultimate
toughness was derived by calculating the area under the
stress–strain curve. Figure 10b shows an overview of the
Fig. 10. (a) Elongation at break for various print orientations. PETG 0°is not added due to high value, (b) Ultimate Toughness of the
specimens (PETG 0°not included), (c) Yield Strength for various raster angles of ABS, PETG and PLA materials, (d) Average Ultimate
Strength for various raster angles of ABS, PETG and PLA materials (e) Tensile Modulus of test specimens
6856—Volume 30(9) September 2021 Journal of Materials Engineering and Performance
ultimate toughness of the printed specimens. It should be noted
that the 0°raster angle of PETG specimen is not mentioned in
this figure due to its very high amount of toughness [4526 J/
m3]. Accordingly, the ABS specimens exhibited very low
ultimate toughness, with the exception of a 0°raster angle
relative to the PLA and PETG components. In general, PETG
demonstrated the highest amount of ultimate toughness.
3.4 Yield Strength and Ultimate Strength
Figure 10c and d shows the summary of yield strength and
ultimate strength of ABS, PLA, and PETG specimens. The first
assessment of the data sets the highest strengths in the PLA and
a relatively similar amount of yield and ultimate strength for
ABS and PETG specimens with PETG having slightly higher
values. At 0°raster angle, PETG shows an average ultimate
strength of 49.3 MPa with a deviation of 0.4 MPa, ABS shows
an average strength of 38.7 MPa with a deviation of 1.9 MPa,
and PLA has an average strength of 60 MPa with a deviation of
5.1 MPa. A similar trend was observed for other angles as
depicted in Figure 10d. According to Figure 10c and d, PETG
has its maximum strength values if printed in 0°raster angle or
its combinations, such as 0/90°. PLA had the highest values of
yield and ultimate strength. In general, ABS exhibited the
lowest strength values. The ultimate strength of PLA 45/135°
was observed to be as close as that of PLA 0°, but its yield
strength is the same as PLA 0/90°, which is due to higher
toughness at 45/135°. ABS has its high strength at 0°raster
angle. At 45°and 45/135°, ABS has slightly lower ultimate and
yield strength than the longitudinal orientation.
3.5 Tensile Modulus
Figure 10e provides a summary of the average tensile
modulus of the specimens. The tensile modulus was derived
using secant modulus of the elastic area prior to the yield point
of the stress–strain curve. In general, the data show no
significant difference in the tensile modulus of ABS and PETG.
However, PLA exhibited a higher tensile modulus compared to
the ABS and PETG specimens with its highest deviation at 0°
raster angle.
3.6 SEM Micrography
The general overview of the SEM micrographs for all
specimens shows a weak interlayer adhesion in the middle
section of the printed parts. Figure 11a and b shows the
transition of the weak and strong interlayer adhesions of ABS-
90°in the middle section of the specimen. A similar trend is
observed in all three materials’ 90°raster angle combinations
(e.g., 0/90°).
The majority of PLA and ABS exhibited brittle behavior in
all sections of fracture surfaces. In contrast, PETG-0/90°
specimens displayed both ductile and brittle fracture behavior,
as seen in Figure 12. Figure 12a displays the transition between
ductile and brittle behavior. Figure 12b and c depicts the middle
section and the corner of the PETG 0/90°, respectively.
Figure 12c exhibits two types of brittle fracture behavior, in
which the wall of the printed specimen exhibits an uneven
surface fracture.
PETG 90°is an exception that exhibited a complete brittle
fracture. Figure 13 shows brittle fracture in the middle section
of the printed specimen with non-adhered filaments of the
PETG 90°at the bottom of the photograph.
Figures 14a and b depict an example of common defects
other than inter-bead voids that were observed in the PETG
specimens. Figure 14a represents a lack of adhesion between
deposited layers. Figure 14b is an example of crack propagation
in areas where the materials depict a brittle behavior. These
deficiencies are the main reasons for the lower strength and
strain in raster angles other than 0°.
Figure 15 is an example of good adhesion between
deposited filaments in PETG 45/135°. The ductile behavior
of the well-adhered layers is clearly observed.
PLA 45°and 45/135°raster angles exhibited superior
mechanical properties compared to other raster angles of PLA.
Figure 16a shows relatively smaller inter-bead voids in PLA
45°and PLA 45/135°, respectively. These smaller inter-bead
voids contribute to better mechanical properties of the printed
parts.
4. Discussions
Based on the data obtained in this study, the majority of the
samples revealed their highest and lowest mechanical proper-
ties (e.g., elongation and strength) at 0°and 90°raster angles,
respectively. However, PLA is an exception; when compared to
ABS and PETG, the 45°and 45/135°angles of the raster tend
to be favorable for PLA. Among PLA samples, PLA 45/135°
exhibited the highest elongation at break and ultimate tough-
ness. The void-free spots in PLA 45/135°, as shown in
Fig. 11. (a) Weak interlayer transition, (b) weak interlayer in the middle part of ABS 90°
Journal of Materials Engineering and Performance Volume 30(9) September 2021—6857
Figure 16b, explain the reason behind its superior mechanical
properties.
Comparing all materials, the interlayer voids were consid-
erably smaller in PLA. In addition, PLA shows a high deviation
in 0°raster angle, which points to unsteady configuration in this
particular direction, compared to other raster angles.
The angles of 45/135°and 0/90°raster angles were expected
to display an average mechanical property for PETG, ABS, and
PLA specimens, as they contain two high angles. This was true
for PETG and PLA. However, ABS with 0/90°raster angles
displayed little elongation. Also, its deposited layers formed
some wave patterns, as shown in Figure 17, which were
insignificant in PLA and PETG samples. This is because some
irregular adhesion between layers at various locations exists.
For instance, as shown in Figure 11, there is a sufficient
adhesion at the corner of the samples, where the temperature of
previously deposited layer is still high and the layer is just
being deposited. However, the temperature difference of
previous and newly deposited layers in the middle section is
more pronounced in ABC samples than PLA and PETG
samples, which can be attributed to its glass transition
temperature. The glass transition temperature of ABS, PLA,
and PETG are 105, 70, and 80°C, respectively. This causes
poor adhesion and wave patterns in ABS specimens. Further,
Fig. 12. SEM micrographs of PETG 0/90°. (a) Brittle to ductile transition, (b) ductile area, (c) contour with uneven fracture behavior
Fig. 13. Lack of adhesion in PETG 90°layers
Fig. 14. SEM micrographs of PETG 45°specimen, a. lack of adhesion between deposited layers, b. example of crack
6858—Volume 30(9) September 2021 Journal of Materials Engineering and Performance
Figure 18 shows weak interlayer adhesions even when the
materials were printed at the manufacturer’s recommended
temperatures. The small inter-bead voids in the Figure 18b
suggests that the recommended deposition temperature is not
high enough to melt materials. This effect was not observed in
PLA and PETG, which stresses the poor printing capability of
ABS compared with PETG and PLA.
Figure 19a and b exhibits the thin bonding areas of PETG
samples, and subsequently weak interlayer adhesion, which
results in lower mechanical properties for PETG 90°and PETG
45°samples. In general, weak interlayer adhesion causes inter-
raster fusion bond failure mode, which lowers the strength of
specimens. Figure 19c shows a huge gap in a group of
deposited layers that can be another cause of the failure in the
PETG samples.
In most cases, PETG is superior to ABS in terms of tensile
strength, yield strength, strain at break, and toughness.
However, ABS samples produced a higher elastic modulus in
a consistent manner. Additionally, PETG has competitive
properties to those of PLA, especially in terms of strength
and elongation. The mechanical advantages of PETG are
apparent when the material is stressed in the same direction of
the rasters. On the other hand, these advantages are not as
apparent due to the weak raster-to-raster adhesion. Nonetheless,
increasing the print temperature may improve its raster bonding
strength. Furthermore, introducing additives to PETG, such as
carbon fiber, glass fiber, and alumina particles may also
Fig. 15. An example of good adhesion in PETG 45/135°
Fig. 16. Voids in FDM specimens (a) PLA 45°, (b) PLA 45/135°
Fig. 17. Wave form of the deposited layers in ABS 90°
Journal of Materials Engineering and Performance Volume 30(9) September 2021—6859
improve the raster lateral bonding, as well as its stiffness and
strength characteristics. Also, it is recommended to select a
print path that allows the forces on the printed part to be
longitudinal to the rasters.
5. Conclusion
The effects of five different raster angle directions were
studied on PETG, PLA and ABS materials in FDM additive
manufacturing. A total of 75 tensile tests were carried out, and
the results were given in terms of stress–strain curves. Further,
the SEM micrograph analysis was performed comprehensively
on the fracture surface of the specimens to investigate the
reasons for the different behaviors in each raster angle. PETG
material showed a high potential in terms of elongation and
toughness, which can be varied by using various raster angles.
PLA has the highest strength and tensile modulus, but exhibits
significant deviation in modulus at 0°raster angle, and it is less
durable than other materials, since PLA, as a material made
from renewable resources (such as corn), tends to lose
properties over the time. Hence, understanding PETG and
other alternative materials is even more important. Due to
notable performance of PETG, there is promising potential for
its increased use in future applications. In this study, the
optimum mechanical properties for PETG were achieved at 0°
and 0/90°raster angles. ABS had the optimum properties at 0°
and 45/135°raster orientations. However, in the case of PLA,
45°and 45/135°raster angles hold higher mechanical proper-
ties than other angles due to lower inter-bead voids. The SEM
micrographs show a consistency in adhesion of PLA-deposited
beads compared to ABS and PETG. PETG specimens had
weak interlayer adhesion, which was the primary cause of
lower mechanical properties in certain raster angles. Currently,
the primary cause of weak interlayer adhesion is unknown.
However, according to the voidsÕshape, increasing PETG
deposition temperature may reduce inter-bead voids. The effect
of various temperatures of the inter-filament adhesion, as well
as the effect of various infill density and cooling rate and
deposition speed on mechanical properties, will be considered
in future studies.
Acknowledgments
The authors would like to thank Prof. Dipankar Ghosh and
Prof. Oleksandr Kravchenko for making available the SEM
machine and the tensile test machine, respectively.
References
1. N.G. Tanikella, B. Wittbrodt and J.M. Pearce, Tensile strength of
commercial polymer materials for fused filament fabrication 3D
printing, Addit. Manuf., 2017, 15, p 40–47. https://doi.org/10.1016/
j.addma.2017.03.005
2. C. Casavola, A. Cazzato, V. Moramarco and G. Pappalettera, Residual
stress measurement in Fused Deposition Modelling parts, Polym. Test.,
2017, 58, p 249–255. https://doi.org/10.1016/j.polymertesting.2017.01.
003
Fig. 18. Weak interlayer adhesion in ABS 0/90. (a) weak interlayer adhesion at the corner of ABS 0/90, (b) weak interlayer adhesion at the
middle part of ABS 0/90
Fig. 19. a and b thin interlayer bonding in PETG 45°C a large gap
6860—Volume 30(9) September 2021 Journal of Materials Engineering and Performance
3. S. Rangisetty and L.D. Peel, The Effect of Infill Patterns and Annealing
on Mechanical Properties of Additively Manufactured Thermoplastic
Composites. In Smart Materials, Adaptive Structures and Intelligent
Systems, 2017, Sep 18, American Society of Mechanical Engineers,
vol. 58257, p V001T08A017
4. N.P. Levenhagen and M.D. Dadmun, Improving Interlayer Adhesion in
3D Printing with Surface Segregating Additives: Improving the
Isotropy of Acrylonitrile–Butadiene–Styrene Parts, ACS Appl. Polym.
Mater., 2019, 1, p 876–884. https://doi.org/10.1021/acsapm.9b00051
5. W. Prasong, A. Ishigami, S. Thumsorn, T. Kurose and H. Ito,
Improvement of interlayer adhesion and heat resistance of biodegrad-
able ternary blend composite 3D printing, Polymers (Basel)., 2021, 13,
p 1–20. https://doi.org/10.3390/polym13050740
6. S. Wojtyła, P. Klama and T. Baran, Is 3D printing safe? Analysis of the
thermal treatment of thermoplastics: ABS, PLA, PET, and nylon, J.
Occup. Environ. Hyg., 2017, 14, p D80–D85. https://doi.org/10.1080/
15459624.2017.1285489
7. S. Ziemian, M. Okwara and C.W. Ziemian, Tensile and fatigue
behavior of layered acrylonitrile butadiene styrene, Rapid Prototyp. J.,
2015, 21, p 270–278. https://doi.org/10.1108/RPJ-09-2013-0086
8. Q. Sun, G.M. Rizvi, C.T. Bellehumeur and P. Gu, Effect of processing
conditions on the bonding quality of FDM polymer filaments, Rapid Prototyp.
J., 2008, 14, p 72–80. https://doi.org/10.1108/13552540810862028
9. S. Guessasma, S. Belhabib and H. Nouri, Printability and Tensile
Performance of 3D Printed Polyethylene Terephthalate Glycol Using
Fused Deposition Modelling, Polymers (Basel)., 2019, 11, p 1220. h
ttps://doi.org/10.3390/polym11071220
10. R.B. Dupaix and M.C. Boyce, Finite Strain Behavior of Poly (Ethylene
Terephthalate) (PET) and Poly (Ethylene Terephthalate)-Glycol
(PETG), Polymer, 2005, 46(13), p 4827–4838
11. L. Yuan, S. Ding and C. Wen, Additive manufacturing technology for
porous metal implant applications and triple minimal surface struc-
tures: A review, 2020 https://doi.org/10.1016/j.bioactmat.2018.12.003
12. G.J. Johnson, Encyclopedia of Analytical Science, 2nd ed., Reference
Reviews, 2005, vol. 19, no. 8, p 38–39. https://doi.org/10.1108/0950
4120510632723
13. E.A. Campo, Selection of Polymeric Materials How to Select Design
Properties from Different Standards Plastics Design Library, 2008. h
ttps://www.sciencedirect.com/book/9780815515517/selection-of-poly
meric-materials
14. C. Ziemian, M. Sharma and S. Ziemi, Anisotropic mechanical
properties of ABS parts fabricated by fused deposition modelling,
Mech. Eng., 2012 https://doi.org/10.5772/34233
15. V.E. Kuznetsov, A.N. Solonin, A.G. Tavitov, O.D. Urzhumtsev, A.H.
Vakulik, Increasing of Strength of FDM (FFF) 3D Printed Parts by
Influencing on Temperature-Related Parameters<strong></stron-
g>of the Process, (2018) 1–32. https://doi.org/10.20944/preprint
s201803.0102.v2
16. J.M. Chaco´n, M.A. Caminero, E. Garcı´a-Plaza and P.J. Nu´n˜ ez,
Additive manufacturing of PLA structures using fused deposition
modelling: Effect of process parameters on mechanical properties and
their optimal selection, Mater. Des., 2017, 124, p 143–157. https://doi.
org/10.1016/j.matdes.2017.03.065
17. K. Durgashyam, M. Indra Reddy, A. Balakrishna and K. Satya-
narayana, Experimental investigation on mechanical properties of
PETG material processed by fused deposition modeling method, Mater.
Today Proc., 2019, 18, p 2052–2059. https://doi.org/10.1016/j.matpr.
2019.06.082
18. R. Srinivasan, P. Prathap, A. Raj, S.A. Kannan and V. Deepak,
Influence of fused deposition modeling process parameters on the
mechanical properties of PETG parts, Mater. Today Proc., 2020, 27,p
1877–1883. https://doi.org/10.1016/j.matpr.2020.03.809
19. R. Srinivasan, W. Ruban, A. Deepanraj, R. Bhuvanesh and T.
Bhuvanesh, Effect on infill density on mechanical properties of
PETG part fabricated by fused deposition modelling, Mater. Today
Proc., 2020, 27, p 1838–1842. https://doi.org/10.1016/j.matpr.2020.
03.797
20. M.M. Hanon, R. Marczis and L. Zsidai, Anisotropy evaluation of
different raster directions, spatial orientations, and fill percentage of 3d
printed petg tensile test specimens, Key Eng. Mater., 2019, 821, p 167–
173.
21. K. Szykiedans, W. Credo and D. Osin
´ski, Selected mechanical
properties of PETG 3-D prints, Procedia Eng., 2017, 177, p 455–
461. https://doi.org/10.1016/j.proeng.2017.02.245
22. B. Akhoundi and A.H. Behravesh, Effect of filling pattern on the
tensile and flexural mechanical properties of FDM 3D printed products,
Exp. Mech., 2019 https://doi.org/10.1007/s11340-018-00467-y
23. B. Rankouhi, S. Javadpour, F. Delfanian and T. Letcher, Failure
analysis and mechanical characterization of 3D printed ABS with
respect to layer thickness and orientation, J. Fail. Anal. Prev., 2016, 16,
p 467–481. https://doi.org/10.1007/s11668-016-0113-2
24. V.E. Kuznetsov, A.N. Solonin, A.G. Tavitov, O.D. Urzhumtsev, and A.
Vakulik, Increasing Strength of FFF Three Dimensional Printed Parts
by Influencing on Temperature-Related Parameters of the Process,
Rapid Prototyp. J., 2020, 26(1), p 107–121. https://doi.org/10.1108/
RPJ-01-2019-0017
25. J. Kierkels, Tailoring the mechanical properties of amorphous
polymers, 2006 https://doi.org/10.6100/IR613293
26. ASTM D618-13, Standard Practice for Conditioning Plastics for
Testing, ASTM International, West Conshohocken, PA, 2013, https://
www.astm.org/Standards/D618.htm
27. Ultimaker, Cura User Manual, 2015, p 28–31. https://ultimaker.com/
software/ultimaker-cura
28. G.M. Swallowe, Ed., Mechanical Properties and Testing of Polymers:
An A–Z Reference. Springer Science & Business Media, 1999
Publisher’s Note Springer Nature remains neutral with regard to
jurisdictional claims in published maps and institutional affilia-
tions.
Journal of Materials Engineering and Performance Volume 30(9) September 2021—6861
