Mechanical properties enhancement of 3D-printed fiber/PLA
composites
Bhargavi Thakre, Suraja, Varun Srinivas, Sudhanshu Verma
ABSTRACT:
This study explores ways to improve the mechanical performance of 3D-printed polylactic
acid (PLA) by reinforcing it with glass fibers using fused deposition modeling (FDM). PLA is
a popular, biodegradable material in additive manufacturing, but its relatively low tensile
strength and limited thermal resistance make it unsuitable for many load-bearing
applications. To address this, the research focused on strengthening PLA by printing it over
pre-arranged glass fibers with specific orientations. Standardized tests—including tensile,
flexural, and creep testing—were conducted to compare pure PLA with glass fiber-
reinforced PLA (GFR-PLA). Interestingly, the results showed that pure PLA performed
better in tensile and flexural tests. This was mainly due to inconsistent bonding and uneven
distribution of the glass fibers in the composite. Creep tests further revealed that PLA
becomes significantly weaker at temperatures close to its glass transition point, leading to
rapid deformation under sustained loads. These findings highlight the importance of strong
fiber-matrix bonding and thermal management when designing reinforced PLA composites.
Overall, this work offers practical insights for optimizing sustainable materials for
structural uses in industries like aerospace, automotive, and healthcare.
1.Introduction
The development of 3D printing technology has revolutionized manufacturing by producing
complex geometries quickly and cost-effectively. Polylactic Acid (PLA) is a leading material
in the field of additive manufacturing due to its biodegradability, renewability, and ease of
processing. However, PLA’s inherent limitations, such as low tensile strength, limited
fracture toughness, and insufficient thermal resistance, restrict its application in high-
performance and load-bearing components. A promising solution to address these
deficiencies is the reinforcement of PLA with various types of fibres, including continuous
fibres, natural fibres, and chopped synthetic fibres. By incorporating such reinforcements,
the mechanical and structural properties of PLA can be significantly improved, enabling its
application in engineering, aerospace, and automotive industries. This project explores the
reinforcement of PLA for 3D printing by drawing upon three significant studies in the
domain.
Composite materials have transformed modern engineering due to their superior
mechanical properties, including high strength-to-weight ratio, corrosion resistance, and
durability. These materials are widely used in aerospace, automotive, and structural
applications, where traditional materials like metals and polymers may fall short in terms of
performance and longevity. The continuous advancements in material science have allowed
researchers to explore various reinforcement techniques to enhance the mechanical,
thermal, and electrical properties of composites, making them suitable for a broad range of
applications (14). This research aims to build upon previous findings by conducting a
systematic analysis of the tensile properties of different fibre-reinforced composite
configurations. By evaluating parameters such as fibre orientation and layer deposition
strategies this study seeks to provide a deeper understanding of how these factors influence
the overall performance of composite materials. The findings will contribute to the
development of next-generation composite materials that can meet the demanding
requirements of aerospace, automotive, and industrial applications (15). Much has changed
in the field of continuous fiber-reinforced composites since Matsuzaki et al. first
documented their research on the Fused Deposition Modeling (FDM) method. This
foundational work has led to the publication of many studies, which have contributed to the
development of Continuous Scaled Manufacturing (CSM), introduced in 2012 using the
Stereolithography (SLA) method [1]. The market for additive manufacturing (AM) has
grown substantially; in 2018, revenues worldwide reached $14.5 billion, surpassing what
was initially estimated for the year 2020[1]. The advantages of 3D printing, including the
product customization flexibility, rapid prototyping ability, and lower cost, have promoted
its adoption across various industries. Fused Filament Fabrication (FFF) is an extremely
popular form of AM used dominantly within the aerospace, automotive, and biomedical
fields, which have successfully applied it for the efficient processing of thermoplastic
polymers and composites [2]. PLA is widely used in FFF as it is biodegradable,
biocompatible, and renewable. In excessive amounts, it is utilized in packaging, automotive,
and biomedical applications. However, the mechanical properties of 3D-printed parts made
of PLA are affected by building orientation and layer height so further research into its
fracture behaviour is required [3]. Continuous fiber-reinforced composites have been
developed to improve the mechanical properties of 3D-printed components, which have
traditionally not been able to compare with conventional materials. The use of additives,
such as lignin (LIG), has shown promise for improving the characteristics of PLA for use in
healthcare, offering both antioxidant and antimicrobial benefits [4]. The most recent
developments in AM have allowed for metamaterials with special mechanical properties,
such as tailored deformation responses and increased resistance to fatigue. Some studies
have demonstrated that print parameters, including raster orientation, are crucial factors
influencing the mechanical performance of 3D-printed PLA components [5]. Hence, use of
AM in biomedical fields is on the rise. It is potential due to the development of bone and
joint implants from materials like Hydroxyapatite (HA). Although there are mechanical
strength-related difficulties, 3D printing gives an efficient route to the manufacturing of
customized implants with improved biocompatibility [6]. This paper discusses
experimental and numerical analyses related to the tensile failure behaviour of 3D-printed
polylactic acid (PLA), using digital imaging correlation in combination with finite element
method assessments for several raster orientations [7]. As AM techniques are gaining
popularity, there is a greater need for optimizing process parameters for better mechanical
properties of printed parts. This paper aims to address the existing knowledge gaps by
considering novel PLA composite filaments and their applications across different
industries [8].
In paper [9] studied the mechanical performance of PLA filament (pure and with SCF)
reinforced with continuous carbon fiber and presents a comprehensive tensile and flexural
response of CCFRPC and to investigate the fracture interface after performing the
mechanical testing through optical microscope. Research investigations on the possibility of
reducing the strain/stress concentrations in an open-hole plate using localized 3D printed
carbon fiber reinforcements. The use of a recent manufacturing process, based on the
additive manufacturing technique, has allowed arbitrary reinforcements to be created in the
open-hole plate. Experimental tests, analytic and numerical analyses have been performed.
The specimens have been produced by means of the 3D printer Mark Two provided by Mark
forged® and they have been tested under a uni-axial load. The digital image correlation
technique, DIC, has been used to evaluate the strain field during the test [10]. The study
[11] used carbon fiber-ABS composites and used as FDM feedstocks. Short carbon fiber-
reinforced ABS composites at different fiber loadings were prepared by both compression
moulding (CM) and FDM to assess the strengths and weaknesses of the FDM process (in
comparison with the more conventional CM process). Effects of the process and fiber
loading on void formation, average fiber length, and fiber orientation distribution, and
eventually their effect on the tensile strength and modulus of the final printed product,
were investigated. The performance of the Mark forged Mark One system is also evaluated
for the fabrication of composites with continuous fiber reinforcement. This study involved
the fabrication of nylon composites with carbon, Kevlar, and glass fibres (Sourced from
Mark forged) and the mechanical performance of all three composite types were compared.
To date, Mark forged materials have been assessed individually, and under differing testing
conditions and standards. This study presents a comprehensive tensile and flexural
characterization of all fibres commercially available for the Mark forged system under
uniform conditions, facilitating their direct comparison. In addition, the influence of fiber
volume fraction (VF), fiber placement and fiber orientation, on the mechanical performance
of the composite were evaluated [12]. Development of a novel extruder based on the
“Embedding on the component” method to eliminate drawbacks of other methods. This
extruder is interchangeable and can be installed on the available FDM 3D printers. The
quality of 3D printed specimens is examined by doing tensile and bending attests and
morphological analysis [13].
The findings from this project aim to bridge the gap between PLA’s environmental benefits
and its limited mechanical performance. By systematically studying and optimizing the
reinforcement of PLA with continuous fibres, natural fibres, and chopped fibres, this
research seeks to expand the applications of PLA composites in areas requiring higher
strength and durability. Moreover, the integration of sustainable materials like flax fibres
aligns with global efforts toward reducing environmental impact, making this study
relevant for industries prioritizing eco-friendly manufacturing solutions.
2. Materials And Methodology:
2.1 Methodology Chart
Figure 1. Methodology layout chart
The construction procedure comprises utilising a 3D printer to reinforce PLA onto pre-
placed glass fibres on a glass plate. The polymer matrix is commercial PLA filament, and the
glass fibres are randomly orientated or unidirectionally distributed on the glass plate prior
to printing. The fibres' orientation is of rectilinear type with varied infill percentages of PLA
and oriented at angles 45 degrees is changed to examine how it affects the mechanical
properties. The nozzle height of the fused filament fabrication (FFF) 3D printer can be
adjusted to guarantee that PLA is properly deposited onto the fibres. Printing parameters
are optimised to achieve strong interfacial bonding between PLA and the fibres. These
include nozzle temperature (200-220°C), print speed (40-60 mm/s), layer height (0.1-0.3
mm), and printing pattern (rectilinear, gyroid, honeycomb) with different PLA infill
percentages. The initial layer's parameters are carefully controlled to prevent fibre
displacement and assure adhesion.
In order to prevent warping, the samples are allowed to cool naturally after printing, and
any additional fibres growing out of the surface are removed if needed. Tensile, flexural, and
Creep testing are used to assess the PLA/glass fibre composites' mechanical qualities in
accordance with ASTM guidelines. A universal testing machine (UTM) is used for tensile
testing (ASTM D638), which measures tensile strength, Young's modulus, and elongation at
break. Stress-strain curves are studied to evaluate the impacts of fibre orientation. Three-
point bending tests are used in flexural testing (ASTM D790) to assess flexural stiffness and
strength.
Epoxy reinforced with glass fiber samples are required to check the properties of 2 different
orientations of the glass fiber that's going to be used. Samples were created by layering
glass fiber on top of each other and a layer of epoxy between the glass fiber was used as to
form matrix of the composite. A universal testing machine is used to perform the tensile
strength (ASTM D638) Ultimate tensile strength, Young’s modulus, stress-strain graph,
mode of failure are obtained from this test. Flexure test (ASTM D790) is to be formed on the
second sample to check for the following parameters: Modulus of rupture; bending strength
and mode of failure.
Scanning electron microscopy (SEM) is employed for microstructural study in order to
explore fracture mechanisms, fiber-matrix adhesion, and fibre pullout. Fibre arrangement
and the development of voids are examined in cross-sectional pictures using optical
microscopy. Mechanical qualities are benchmarked against pure PLA and traditional PLA-
fiber composites, is performed to compare various fibre orientations and printing
conditions. The study is to optimise the reinforcement procedure for improved mechanical
performance and assess the efficacy of depositing PLA on pre-placed glass fibres. To further
enhance composite qualities, future research may investigate various fibre surface
treatments, hybrid reinforcements, and multi-layer fibre designs.
2.2 PLA as Matrix:
Poly Lactic Acid:
Polylactic acid (PLA) is a biodegradable, bio-based thermoplastic polymer synthesized from
renewable agricultural sources such as corn starch, sugarcane, or cassava. Due to its eco-
friendly nature, PLA has gained significant attention in recent years as a sustainable
alternative to petroleum-based polymers (Garlotta, 2001). The polymer can be synthesized
through two primary methods: direct polycondensation of lactic acid and ring-opening
polymerization (ROP) of lactide, with the latter method preferred for achieving higher
molecular weights and improved mechanical properties (Drumright et al., 2000). In terms
of mechanical performance, PLA exhibits a tensile strength in the range of 50–70 MPa and a
Young’s modulus between 2.5–3.5 GPa, making it comparable to common thermoplastics
such as polyethylene terephthalate (PET). However, PLA suffers from low elongation at
break (2–10%), making it relatively brittle and less impact-resistant compared to
alternatives like ABS (Auras et al., 2004). It has a glass transition temperature of 55–60°C
and a melting point ranging from 160–180°C, which restricts its use in high-temperature
environments.
One of the most notable advantages of PLA is its biodegradability. Under industrial
composting conditions—typically above 58°C with high humidity—PLA can degrade into
carbon dioxide and water within a few months (Jamshidian et al., 2010). This property has
led to its widespread use in environmentally conscious applications such as disposable
packaging, agricultural films, and biomedical devices including sutures and implants.
Despite its favourable properties, PLA’s inherent brittleness and low thermal resistance
limit its use in structural applications. To address these shortcomings, researchers have
explored modifications such as blending with ductile polymers (e.g., PBAT, PEG) and
reinforcing with fibres like glass or carbon to improve mechanical and thermal
performance. These advancements expand the usability of PLA in load-bearing applications
and functional parts, especially in the field of additive manufacturing (Drumright et al.,
2000; Jamshidian et al., 2010).
2.3.Glass fibers as Reinforcement :
Glass fibres are high-performance reinforcing materials produced from silica-based
compositions, commonly utilized in fibre-reinforced polymer (FRP) composites due to their
excellent mechanical strength, chemical resistance, and low cost. The production of glass
fibres involves the high-temperature melting of raw materials—primarily silica (SiO₂),
alumina (Al₂O₃), lime (CaO), magnesia (MgO), and boric oxide (B₂O₃)—followed by
extrusion through fine orifices and rapid cooling to form continuous filaments (Mallick,
2007). Among various types, E-glass (electrical grade) is the most widely used for structural
applications due to its balanced mechanical and electrical insulation properties. It possesses
a tensile strength of 2000–3500 MPa, a Young’s modulus of 70–80 GPa, and a density of
2.54–2.60 g/cm³ (Bunsell & Renard, 2005). Other variants include S-glass, known for
superior tensile strength and thermal stability, and C-glass, which offers high chemical
corrosion resistance.
Figure 2. Glass fibre as reinforcement with PLA matrix sample fabrication
The low thermal expansion coefficient (~5 × 10⁻⁶/°C) and melting point of approximately
1120–1250°C make glass fibres thermally stable for demanding applications (Callister &
Rethwisch, 2020). Furthermore, they absorb minimal moisture (<0.1%), maintaining
performance even in humid or corrosive environments. However, their inherently brittle
nature and susceptibility to matrix debonding require appropriate surface treatments—
commonly with silane coupling agents—to enhance interfacial adhesion in polymer
matrices (Mallick, 2007). In composite materials, the addition of glass fibres significantly
enhances the mechanical behaviour of thermoplastics such as polylactic acid (PLA).
Improvements include increased tensile and flexural strength, higher stiffness, and better
dimensional stability under load. The effectiveness of reinforcement depends on factors like
fibre aspect ratio, volume fraction, orientation, and dispersion uniformity (Bunsell &
Renard, 2005). Short glass fibres are often preferred in 3D printing applications for ease of
processing, whereas continuous fibres offer superior load-bearing capacity.
Due to these advantages, glass fibres are extensively used in sectors such as automotive,
aerospace, construction, electronics, and additive manufacturing, where strength-to-weight
ratio and environmental durability are crucial.
3.METHODOLOGY AND MAKE:
3.1.3D PRINTER :
In this study, 3D printing was employed for the fabrication of specimens using a fused
deposition modelling (FDM) technique. The printing process was carried out using a
Creality Ender 3 desktop 3D printer, a widely used, open-source FDM machine recognized
for its affordability and reliability in producing thermoplastic components with moderate
precision. The printer features a layer resolution of 100–200 microns, a build volume of 220
× 220 × 250 mm, and a 0.4 mm brass nozzle. It supports a range of thermoplastic filaments
including PLA, ABS, PETG, and TPU.
The Ender 3 operates with a Cartesian coordinate system and utilizes a heated bed capable
of reaching temperatures up to 110°C, which improves adhesion and minimizes warping
during printing. The nozzle temperature is controllable up to 260°C, making it suitable for a
variety of filament materials. In this research, PLA filament was used due to its
biodegradability and ease of processing, with the nozzle and bed temperatures maintained
at 200°C and 60°C, respectively. Slicing of the 3D models was performed using Ultimaker
Cura software (version X.X), where printing parameters such as infill density, layer height,
print speed, and support generation were configured
Figure 3a.,3b. PLA neat filament, 3D printer:Creality
4.EXPERIMENTATION:
4.1.TENSILE TEST:
The tensile test sample has a rectangular profile with a specially designed tapered section in
the middle. This tapering begins at 130 mm from one end and extends over a length of
1150.68 mm, featuring a curvature radius of 760 mm. The overall length of the sample is
1650 mm, with a width of 190 mm and a thickness of 32 mm.
This shape ensures that the maximum stress is concentrated in the tapered section during
the test, promoting failure in the region intended for accurate assessment. Its design
minimizes stress concentrations near the grips, ensuring reliable and consistent test results.
The dimensions are tailored for compatibility with standard tensile testing equipment.
Figure 4.CAD drawing of tensile sample
Figure 5. Tensile Test Setup
The tensile test was conducted using a standardized specimen with a gauge length of 50
mm. The gauge length is the region of the specimen where strain measurements are
focused, ensuring precise evaluation of the material's deformation during testing. The
sample featured a flat rectangular cross-section with a width of 13 mm and a thickness of 3
mm, optimizing stress distribution and minimizing localized stress concentrations. Testing
was performed at a controlled velocity of 50 mm/min, which refers to the constant rate of
separation between the machine grips. This velocity plays a critical role in determining
strain rate sensitivity and ensures uniform test conditions for the evaluation of the
material's tensile properties, including yield strength, ultimate tensile strength, and
elongation at break.
4.2.FLEXTURE TEST:
As mentioned above the test sample for flexure test were made using fusion deposition
modelling (FDM) manufacturing was used to make a test sample with 100% fill with
rectilinear walls. As for the GFRP test sample the FDM printing process was paused halfway
where a pre-cut sheet of glass fibre was placed, and the printing process was resumed. The
2 samples are identical in dimensions (12.7mm x 127mm x 3mm) and were modelled
according to the ASTM D790 standards. Tests on the tension were done at a controlled rate
of 10 mm\min based on the specification mentioned in the standard. Fig shows a 3 point
flexure test being performed on the fabricated test samples.
Figure 6. CAD drawing of Flexure Sample
Figure 7a. Flexure test setup before bending Figure 7b. Flexure test setup after bending
The machine used to perform the 3-point flexure test is the Tinius Olsen H25KT and the
following graphs and table covers the mechanical response to each of the specimen for
identical loading conditions.
4.3.CREEP TEST:
To investigate the time-dependent deformation behavior of reinforced thermoplastics
under sustained load, creep test specimens were fabricated using fused deposition
modeling (FDM) and subjected to constant load at elevated temperature conditions. The
material system comprised polylactic acid (PLA) as the polymer matrix, reinforced with a
single-layer fiberglass sheet embedded mid-plane during the 3D printing process. The
specimens were manufactured using a Creality FDM 3D printer, employing a rectilinear
infill pattern with 100 % density to balance strength and material usage. The layer height
was set to 0.2 mm, and printing was paused at a layer height of 2.5 mm to manually place
the glass fiber sheet. A minimal adhesive was used to ensure the fiberglass remained
properly aligned during continuation of the upper layers. After completion, the creep test
samples had a nominal thickness of 5 mm, with fiberglass reinforcement encapsulated
centrally. Dimensional stability and uniformity of fiber placement were verified through
visual inspection. At the same time, samples for PLA-neat and PLA-with walls with 100%
infill and rectilinear configuration were printed to study test results.
Figure 8a.,8b. CAD Drawing for creep test according to machine requirement
The completed specimens were subjected to creep testing under a constant applied load of
25 kg (approximately 245 N). To simulate thermal conditions near the softening point of
PLA, testing was conducted at an elevated temperature of 55 °C using a controlled heating
environment. The load was uniformly distributed across the surface of the specimen. Creep
deformation was measured by recording dimensional changes at regular time intervals. The
testing procedure was designed to evaluate the viscoelastic response and dimensional
stability of the reinforced PLA under combined thermal and mechanical stress.
Figure 9: Creep test experimental setup
5.RESULTS AND INTREPRETATIONS:
5.1.TENSILE TEST:
Tensile tests were conducted to evaluate and compare the mechanical behavior of glass
fiber-reinforced polymer (GFRP) and pure polylactic acid (PLA) specimens. The results
highlight notable differences in their tensile performance, particularly in terms of ultimate
stress, elongation, and deformation characteristics. The GFRP specimen exhibited an
ultimate stress of 37.6 MPa, with a break distance of 2.44 mm and a total elongation of
3.49%. In comparison, the pure PLA specimen demonstrated superior tensile properties,
achieving an ultimate stress of 43.4 MPa, a break distance of 2.86 mm, and a significantly
higher elongation of 5.72%. These findings indicate that pure PLA outperforms GFRP in
terms of both tensile strength and ductility under the specified testing conditions.
Figure 10. Tensile test results for the sample reinforced with Glass fibers
Figure 11. Tensile test results for neat PLA
The force versus extension and stress versus strain curves further emphasize these
distinctions. The GFRP specimen reached a maximum load of 1350 N, whereas the pure PLA
specimen sustained a higher maximum load of 1690 N. The stress-strain curve for GFRP
depicted linear behavior up to failure, characteristic of a brittle material. In contrast, the
curve for pure PLA demonstrated higher strain at failure, suggesting enhanced flexibility
and ductile behavior. In summary, while GFRP offers acceptable tensile strength, pure PLA
exhibits superior performance with higher strength and elongation. These observations
underline the potential advantages of pure PLA in applications where ductility and tensile
strength are critical. However, the material selection ultimately depends on the specific
requirements of the application.
Figure12.Tensile test samples after damage
The observed discrepancies in the tensile performance of the GFRP specimen, as compared
to pure PLA, may be attributed to inconsistencies in the bonding process between the PLA
matrix and the glass fibers during sample preparation. The method of integrating the
reinforcement material plays a critical role in determining the composite's mechanical
properties. Inadequate bonding or improper dispersion of the glass fibers can result in
stress concentrations, void formations, or poor load transfer across the fiber-matrix
interface, ultimately leading to suboptimal performance. Such issues could manifest as
reduced tensile strength and elongation, as observed in the GFRP samples tested. Further
investigation into the fabrication process, including optimization of bonding techniques and
quality control during specimen creation, is necessary to mitigate these potential sources of
error and enhance the mechanical performance of the composite material.
5.2.FLEXURE TEST:
PLA clearly outperforms glass fiber reinforced PLA in all the aspects of the test showing
superior mechanical properties. PLA is better at load bearing as evident from the force
versus position graph it was able to take 69.2 N and it reinforced counterpart only taking up
to 35.8 N. Comparing the stress strain graph of the two materials shows that PLA has a
ultimate tensile stress as 63.5 MPa and the glass fiber reinforced PLA having 32.9 MPa, also
PLA having a slightly steeper curve when compared Glass fiber reinforced PLA indicates
that PLA has a relatively higher flexure modulus.
Figure 13. Flexure test results of Glass fiber reinforced PLA
Figure 14. Flexure test results of neat PLA
MATERIAL Ultimate Load Ultimate Load Total Elongation
PLA 69.2 N 63.5 MPa 6.28 %
GFR-PLA 35.8 N 32.9 MPa 3.37 %
Table 1. Flexure test results
PLA elongates to max of 6.28% which is significantly larger than the 3.2% expansion of the
glass fiber reinforced PLA has undergone proving that adding glass fiber as a reinforcement
in this method effectively decreases its ductile property making the final material more
brittle.
This counter intuitive results for the mechanical properties of GFRP might be because of the
inconsistent bonding of the glass fiber to the PLA matrix. Inadequate bonding or uneven
distribution of the glass fibers across the matrix result in stress concentrations, void
formations, or poor load transfer across the fiber-matrix interface, ultimately leading to
suboptimal performance.
Such issues could manifest as reduced strength and elongation, as observed in the GFRP
samples tested. Further investigation into the fabrication process, including optimization of
bonding techniques and quality control during specimen creation, is necessary to mitigate
these potential sources of error and enhance the mechanical performance of the composite
material.
5.3.CREEP TEST :
The following are the creep test results, and the strain vs time graph illustrates the creep
failure happening in PLA-neat sample and PLA-with 6-layer walls sample.
Figure 15: Creep strain vs time graph of PLA – without walls
At 55 °C, which is close to the glass transition temperature (Tg) of PLA (~60 °C), the
polymer experienced thermal softening, resulting in a rapid onset of tertiary creep. The
strain-time curve shows a sharp rise in strain after a short initial delay, leading to material
rupture. This behavior is characteristic of polymers nearing their softening point, where
molecular mobility increases significantly, reducing resistance to deformation. The short
time to failure and the sudden spike in strain confirm that thermal effects critically weaken
the mechanical integrity of PLA under sustained loading.
Figure 16 :Creep strain vs time graph of PLA – with walls
At 30 °C and with walls , well below PLA’s glass transition temperature, the polymer
maintained better structural stability. The strain developed gradually over time, showing a
prolonged primary and secondary creep stage before reaching maximum strain. The
specimen sustained the load for a longer duration without catastrophic failure, highlighting
improved creep resistance at this temperature. The gradual increase in strain and delayed
failure indicate that viscoelastic properties dominate at lower temperatures, allowing the
material to deform without immediate rupture.
Parameter At 30 °C At 55 °C
(with walls)
Max Strain (%) 19.814 13.760
Max Extension (mm) 9.907 6.880
Time to Failure 6 min 15 sec 3 min 52 sec
Creep Behavior Gradual deformation Rapid softening & failure
Table 2. Creep test results of PLA (neat) and PLA with walls
Despite the higher maximum strain at 30 °C, the creep process was stable and sustained. In
contrast, at 55 °C, though the final strain was lower, the deformation occurred quickly and
ended in premature failure due to thermal softening and chain relaxation in the polymer
structure. This suggests that temperature plays a more dominant role than strain
magnitude in determining the failure mode in PLA during creep loading. The experiment
demonstrates that PLA's creep resistance decreases significantly at elevated temperatures,
nearing its softening range. Designers and engineers should therefore avoid prolonged
mechanical loading of PLA components at temperatures above 50 °C, especially in structural
or load-bearing applications. These findings are crucial for thermal stability assessments of
PLA-based parts used in environments with fluctuating or high temperatures.
6.CONCLUSION:
This experimental study on reinforcing PLA with glass fibers via FDM 3D printing revealed
both promise and pitfalls. PLA’s eco-friendly profile and ease of processing remain
attractive, but its mechanical shortcomings must be addressed for load-bearing uses. In our
tensile and flexural trials, pure PLA surprisingly outperformed the glass fiber–reinforced
samples. Post-test analysis showed that inconsistent adhesion at the fiber–PLA interface
and uneven fiber placement during printing created weak zones where stress concentrated
rather than transferring smoothly into the stiffer glass fibers. Tiny gaps and voids along the
fiber surfaces prevented effective load sharing, so instead of boosting strength, the fibers
acted as crack-initiation sites—undermining the very reinforcements intended to
strengthen the material.
Creep testing further underscored PLA’s heat sensitivity: at temperatures close to its glass
transition, the polymer softened rapidly and deformed under sustained load, and the
loosely bonded fibers offered no real resistance to this movement. These results drive home
one key lesson: fiber adhesion is as crucial as fiber selection. To achieve meaningful
improvements, future work must focus on enhancing the fiber–matrix bond—through
surface treatments like silane coupling agents—optimizing fiber alignment for even stress
distribution, and fine-tuning printing parameters (nozzle height, extrusion rate) to
eliminate voids. By addressing these interfacial challenges and exploring hybrid or
multi-layer reinforcement strategies, we can unlock the full potential of sustainable,
high-performance PLA composites.
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