Scientia et Technica Año XXVI, Vol. 26, No. 01, marzo de 2021. Universidad Tecnológica de Pereira. ISSN 0122-1701 y ISSN-e: 2344-7214
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Abstract The use of natural fibers as reinforcement for
composite materials is on the rise due to the need to reduce
environmental damage and manufacture sustainable products.
One of the fibers used for this purpose is fique fiber. This article
describes the manufacture of a student chair with fique fiber-
reinforced composite material. To choose the amount of
reinforcement to be used in the elaboration of the chair, the
mechanical characterization of several composites with different
percentages of the fiber was carried out, where it was found that
both the flexural and tensile properties increased with a higher
insertion of fique. The selected material was analyzed
morphologically with optical microscopy, finding that there was
good adhesion between the fiber and the matrix. A simulation with
finite elements showed that the chair would resist a load of 100 kg.
The student chair was manufactured using the Hand Lay Up
technique with material composed of fique fiber and polyester
resin.
Index Terms Composite, Fique, Mechanical characterization,
Natural Fiber.
ResumenEl uso de fibras naturales como refuerzo de materiales
compuestos esta aumentado debido a la necesidad de reducir el
daño ambiental y manufacturar productos sustentables. Una de
las fibras utilizadas para este fin es la fibra de fique. El presente
artículo describe la fabricación de una silla estudiantil con
material compuesto reforzado con fibra de fique. Para la elección
de la cantidad del refuerzo a utilizar en la elaboración de la silla se
realizó caracterización mecánica de diversos compuestos con
diferentes porcentajes de la fibra donde se encontró que tanto las
propiedades de flexión y tensión aumentaron con mayor inserción
de fique. Se analizó morfológicamente con microscopia óptica el
material seleccionado encontrándose que existe buena adhesión
entra la fibra y la matriz. Una simulación con elementos finitos
permitió evidenciar que la silla resistiría una carga de 100 kg. La
This manuscript was sent on September 07, 2020 and accepted on November
11, 2020.
This work was supported by the Universidad Pontificia Bolivariana.
S. mez S. Author is with the Mechanical Engineering Department,
Universidad Pontificia Bolivariana, Km 7 autopista via Piedecuesta,
Floridablanca, Santander, Colombia, (e-mail: sergio.gomezs@upb.edu.co)
E. Cordoba T. Author is with the Mechanical Engineering Department,
Universidad Pontificia Bolivariana, Km 7 autopista via Piedecuesta,
Floridablanca, Santander, Colombia, (e-mail: edwin.cordoba@upb.edu.co)
silla estudiantil se manufacturó por medio de la técnica Hand Lay
Up con material compuesto de fibra de fique y resina de poliéster
Palabras clavesCaracterización mecánica, Fibra Natural,
Fique, Material Compuesto
I. INTRODUCTION
OMPOSITE materials are defined as the heterogeneous
combination of two or more materials at the macroscopic
level in order to achieve better properties than individually [1].
In the manufacture of these composite materials, fibers of
synthetic origin were usually used as reinforcement, however,
recently natural fibers have been replaced because they exhibit
good properties such as high mechanical resistance, excellent
thermal insulation, good flexibility and biodegradability [2].
Additionally, there is a great need to replace unsustainable
products with sustainable products due to the limited amount of
conventional energy resources and damage to the environment,
which has promoted the use of renewable raw materials such as
natural fibers for the development of new components [3].
One of these natural fibers is fique fiber, which is grown in
South American countries such as Colombia, Brazil, Ecuador,
Venezuela, Costa Rica, and the Antilles. The main application
of the fiber is the use of long fibers to make coffee bags and
ropes, however, it is also obtained in other presentations such
as short fibers and woven [4].
Diverse works of manufacture and characterization of
composite materials made with fique fiber are found in the
literature, obtaining mainly their mechanical, thermal,
morphological and dynamic properties [5][9]. However, there
is not enough evidence of use in industrial applications, except
for Delvasto et al. [10], who manufactured corrugated
composite sheets with cement matrix and fique fiber
C. Vega M. Author is with the Mechanical Engineering Department,
Universidad Pontificia Bolivariana, Km 7 autopista via Piedecuesta,
Floridablanca, Santander, Colombia, (e-mail:
christian.vega.2015@upb.edu.co)
S. Gómez B. Author is with the Mechanical Engineering Department,
Universidad Pontificia Bolivariana, Km 7 autopista via Piedecuesta,
Floridablanca, Santander, Colombia, (e-mail: sergio.gomez.2015@upb.edu.co)
Manufacture of student chair in composite
material reinforced with fique fiber
Fabricación de silla estudiantil en material compuesto reforzado con fibra de fique
S. Gómez-Suarez ; E. Córdoba-Tuta , C. B. Vega-Mesa ; S. Gómez-Becerra
DOI: https://doi.org/10.22517/23447214.24509
Artículo de investigación científica y tecnológica
C
Scientia et Technica Año XXVI, Vol. 26, No. 01, marzo de 2021. Universidad Tecnológica de Pereira.
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reinforcement to be used in the construction sector.
It is for this reason that this article describes the manufacture
of a student chair with composite material reinforced with fique
fiber, characterizing the material mechanically and
morphologically by means of the flexural, tensile and optical
microscopy tests accompanied by a simulation of finite
elements that allowed evidencing that the chair would resist a
load of 100 kg.
II. MATERIALS AND METHODS
A. Materials
Fique fiber in random configuration were used as
reinforcement for the composite materials that make up the
back, seat, and armrests of the chair. They were supplied by the
foundation San Lorenzo in Barichara, Santander Colombia. Fig.
1 shows the fiber under an optical microscope at 50X.
Fig. 1. Fique fibers seen with 50X magnification.
The fibers have a length of 1.76 ± 0.53 mm and a diameter of
0.0253±0.0033 mm, as reported in study by Gómez et al. [11],
where the same reinforcement was used in the same random
configuration.
In the fabrication of the chair support structure, fique fiber
was used in woven configuration (See Fig. 2), which was
obtained from a conventional sack used for coffee
transportation.
Fig. 2. Fibers in woven configuration.
The matrix for the different parts of the chair was polyester
reference 102, acquired at the ingequimicas company in
Bucaramanga, Santander, Colombia, being the one with the
lowest viscosity available by the distributor, this in order to
facilitate its handling and application. The percentage of
catalyst resin by weight was 100: 2 respectively.
B. Manufacture of specimens for characterization tests.
Composite material specimens were made with three, four
and five layers of fique reinforcement corresponding to
15.36%, 20.09% and 24.9% by weight, in order to determine
the most suitable arrangement to use on the back, seat and
armrests according to loads to flexural and tensile.
The specimens were manufactured according to the Hand
Lay Up technique, placing layer after layer of fiberglass pre-
impregnated with polyester resin on an acrylic mold previously
anointed with a release agent. Curing was carried out at room
temperature for 48 hours.
The geometry of the specimens for the tensile test was
established according to the ASTM D3039 / D3039M standard
where measurements of 25 cm long by 2.5 cm wide by 2.5 mm
thick are defined.
Regarding the flexural test, the dimensions of the specimens
were established according to the ASTM D7264 / D7264M
standard where the thickness-span ratio was 32: 1 respectively,
and the width was 13 mm. In Fig. 3 specimens manufactured
for the flexural test are observed.
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Fig. 3. Fique fiber specimens.
C. Tensile test.
The tensile test was carried out following the ASTM
D3039/D3039M standard on a universal machine brand MTS
model C43.104 of 10 kN at a speed of 2 mm/min with a
temperature of 24.2 °C ± 3 °C. For each of the materials, five
specimens were tested, considering the average of each of the
properties.
D. Flexural test.
The flexural test was carried out according to the ASTM
D7264/D7264M-15 standard by means of a universal machine
MTS model C43.104 of 10 kN at a speed of 1 mm/min and a
temperature of 24.3 °C ± 3.2 °C.
The flexural mechanical characterization was carried out
with the use of three points as shown in Fig. 4.
Fig. 4. Bending test.
E. Optical microscopy test
Optical microscopy was performed using ZEISS optical
microscope model AXIO scope A1, at increases of 20X, 50X,
100X. The images were captured at different focal planes for
analysis. The analysis was performed on the compound
manufactured with five layers.
F. Finite element analysis
For the finite element analysis, the commercial software
Ansys 2020 academic research was used. A static analysis was
carried out applying a perpendicular load to the surface of the
seat, armrests, and backrest, equivalent to 100 kg-f with fixed
restrictions at the support points where the pieces would be
assembled with screws. The material was assumed to be
homogeneous and its properties were defined in the software
according to the results obtained from the flexural and stress
tensile of the five-layer composite material.
III. RESULTS
A. Tensile test.
As can be seen in Fig. 5, an increase in the tensile mechanical
properties of the composite is evidenced with the addition of a
quantity of fique fiber.
Fig. 5. Tensile strength of composite materials reinforced with fique fibers.
A maximum stress of 27.30 MPa is obtained in the 5-layer
composite.
In Fig. 6 the variation of the elasticity module is observed
where it is evident that it is increased in the composite with the
addition of more quantity of fiber in its manufacture.
Fig. 6. Modulus of elasticity of composite materials reinforced with fique
fibers.
0
5
10
15
20
25
30
35
2 3 4 5 6
Tensile Strength (MPa)
Number of layers
0
0.2
0.4
0.6
0.8
3 4 5
Modulus of elasticity
(GPa)
Number of layers
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A maximum modulus of elasticity is obtained in the five-
layer material being 0.725 GPa.
The mechanical properties of the tensile stress and the
modulus of elasticity increased as more layers of fique were
incorporated into the biocomposite, which resulted in the
material suffering from a stiffening phenomenon. This behavior
was also obtained by Hidalgo et al. [12] in the study of the stress
behavior of a composite material with a polyethylene/aluminum
matrix, varying the amount of fique used as reinforcement.
According to Gañan et al. [13] chemical treatments to the
fique fiber improve the mechanical properties of the composite
since it increases the adhesion between the matrix and the fiber.
For that reason, for future works it is recommended to apply
this type of treatments to the fique.
The results obtained show that the best composite material
for the manufacture of the back, seat and armrests of the student
chair was the one reinforced with five layers of fique.
B. Flexural test.
Fig. 7 shows the flexural stress that was obtained when the
test was applied to the biocomposite with the different fique
layer arrangements.
Fig. 7. Flexural stress of composite materials reinforced with fique fibers.
An increase in flexural stress is evidenced with a greater
amount of fiber used in the composite, reaching the maximum
value of 22.65 MPa with five layers.
This behavior is because the fibers improve the flexural
strength of the resins and that there is load transfer [14].
However, the value obtained of flexural stress in the
composite materials with fique fiber is lower with respect to
those of industrial use, this is due to the low compatibility
between the fiber and the matrix for its different chemical
nature along the interface [15].
The flexural modulus obtained for the different
configurations of layers of composite materials is observed in
Fig. 8.
Fig. 8. Flexural module of composite materials reinforced with fique fibers.
An increase in the flexural modulus is observed with the
increase in the number of fibers, the highest being 1.22 GPa
with the configuration of five layers of fique fibers.
Hidalgo et al. [16] obtained results with the same behavior of
increase in the modulus and flexural stress as the percentage of
fique fiber increased in the LDPE / Al matrix composite.
Likewise, Hidalgo et al. [17] report the same dynamics of
increase in another composite with fique fiber and epoxy and
LLDPE matrix.
It is important to emphasize that the properties of the
composite reinforced with natural fibers do not depend only on
the volume fraction of the fibers, but also on other additional
aspects like the orientation and treatment of the fibers, the
properties of the matrix and the interfacial adhesion between
the fiber and the matrix, in general of the physical and chemical
properties of the constituents of the composite [18].
The results obtained show that the best behavior of the
composite material subjected to flexural loads for the
manufacture of the back, seat and armrests of the student chair,
is the material reinforced with five layers of fique.
C. Optical microscopy.
Fig. 9 and 10 show the five-layer composite material at 20X
and 50X magnification, respectively.
Fig. 9. Micrograph of composite material at 20X.
10
12
14
16
18
20
22
24
26
2 3 4 5 6
Flexural stress ( MPa)
Number of layers
0
0.2
0.4
0.6
0.8
1
1.2
1.4
3 4 5
Flexural Module (GPa)
Numbers of layers
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Fig. 10. Micrograph of composite material at 50X.
As shown in the optical microscopy images, there is good
adhesion between the fiber and the resin since no defects or
spaces between the material's constituents are observed.
In Fig. 11, at 100X magnification, it is evident that the fiber
is completely covered by the matrix, which shows that the fique
was compatible with the polyester resin.
Fig. 11. Micrograph of composite material at 100X.
However, in order to carry out a more conclusive study of the
morphology and the interface of the composite, a study should
be carried out at higher magnifications using scanning electron
microscopy as shown by Barba et al. [19] where they compare
micrographs obtained with optical microscopy and SEM
technique in composite material with recycled constituents.
D. Finite element simulation.
Fig. 12, 13 and 14
[ST1]
show the results obtained from the static
stress analysis for the seat, armrest and back respectively,
carried out in the finite element software Ansys.
Fig. 12. Seat stress analysis.
Fig. 13. Armrest stress analysis.
Fig. 14. Back stress analysis.
Additionally, in Fig. 15, 16 and 17, the results obtained from
the static analysis in deformation for the seat, armrests and back
respectively of the student chair are observed.
Fig. 15. Seat deformation analysis.
Fig. 16. Armrest deformation analysis.
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Fig. 17. Back deformation analysis.
The results of the maximum stresses and the deformation of
the seat, backrest and armrests are shown in Table I.
TABLE I.
MAXIMUM STRESSES AND DEFORMATIONS
Part
Stress (MPa)
Deformation (mm)
Seat
3.4102
6.1981
armrests
6.0211
0.36647
backrest
10.499
9.9646
As can be seen in Table I, the maximum stresses obtained
through the simulation of finite elements are less than the
stresses obtained experimentally for both flexural and tensile,
which allows validating that the chair will support the 100 kg-f
load.
E. Chair manufacturing.
The fique fiber composite material was laser cut in a random
configuration with the geometry of the armrest, seat, and
backrest. With this cutting method, the aim was to improve the
quality of the final finish of the pieces, avoiding dimensional
errors. Fig. 18 shows the laser cut and the different pieces
obtained.
Fig. 18. Laser cutting of parts.
Each of the five layers were impregnated with the polyester
resin using a brush, to ensure uniformity on the surface of the
fibers. They were then stacked on top of each other using the
Hand Lay Up technique. Pressure was applied manually
between each of the layers helping to improve the penetration
of the matrix into the fiber. Fig. 19 shows the process.
Fig. 19. Manufacturing process.
Curing was done at room temperature (23 °C +/- 5 °C) for 72
hours. The manufactured seat and armrest parts are shown in
Fig. 20.
Fig. 20. Armrest and seat manufactured.
For the structure, high density expanded polystyrene molds
were made with the geometry of the different parts that make it
up.
The different profiles of the chair structure were designed
with a diameter of 3 cm. The fiber fabric was impregnated with
polyester resin and rolled up on itself ensuring its compactness
to be introduced into the mold. Long strips of the fabric were
cut to ensure continuous pieces reinforced with the fiber. Fig.
21 shows the manufacturing process used.
Fig. 21. Manufacturing process of the structure.
The curing of the different profiles was carried out at a room
temperature of 24 °C +/- 8 °C for 72 hours. Fig. 22 shows the
manufactured structure.
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Fig. 22. Structure of the chair.
After all the pieces were made in the composite material with
fique fiber, the imperfects present on the surface were
eliminated, using 400 and 600 grit sandpaper.
The assembly of the different parts of the chair was carried
out using a 2” self-drilling screw. Fig. 23 shows the chair
manufactured.
Fig. 23. Manufactured chair.
IV. CONCLUSIONS
The tensile stress and modulus of elasticity of the composite
materials increased with the greater quantity of fibers used, this
due to the stiffening of the material, presenting a maximum
stress of 27.30 MPa and a maximum modulus of elasticity of
0.725 GPa, in the composite material with five layers of fique
fiber (24.9% by weight of the composite).
Likewise, the mechanical properties to flexion of the
composites increased with the insertion of the fiber of fique, the
highest stress obtained being 22.65 MPa with a flexural
modulus of 1.22 GPa in the composite with five layers of fiber
of fique.
The mechanical characterizations showed that the most
suitable material for the manufacture of the back, seat and
armrests of the student chair was the five layers of fique fiber.
On the other hand, the morphological analysis with optical
microscopy allowed observing a good adhesion between fique
fiber and polyester matrix.
With the analysis of finite elements, it was proved that the
chair could support the design load of 100 kg-f since the efforts
generated in the simulation are lower than those obtained in an
experimental way.
A student chair in reinforced composite with five layers of
fiber was manufactured by means of the Hand Lay Up
manufacturing technique, giving an application to the material
of an industrial type.
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Sergio Andrés Gómez S. Was born in
Bucaramanga, Colombia in 1988. He
received the B.S in mechanical engineering
and industrial engineering from
Universidad Pontificia Bolivariana.
Magister in industrial engineering from
Universidad Pamplona, Colombia. He is
currently professor and researcher in the Faculty of Engineering
at Universidad Pontificia Bolivariana.
ORCID: https://orcid.org/0000-0002-6425-7062
Edwin rdoba Tuta was born in
Bucaramanga, Colombia in 1974. He
received the B.S in mechanical engineering
from Universidad Industrial de Santander.
Magister in Mechanical engineering from
Universidad Industrial de Santander,
Colombia. He is currently professor and
researcher in the Faculty of Engineering at Universidad
Pontificia Bolivariana.
ORCID: https://orcid.org/0000-0001-8298-5007
Christian Vega M. Was born in
Bucaramanga, Colombia in 1998. He
received the B.S in mechanical engineering
from Universidad Pontificia Bolivariana in
2020.
ORCID: https://orcid.org/0000-0001-6991-9558
Sergio Andrésmez B. Was born in
Bucaramanga, Colombia in 1994. He
received the B.S in mechanical engineering
from Universidad Pontificia Bolivariana in
2020.
ORCID: https://orcid.org/0000-0001-6464-7944