Scientia et Technica Año XXVI, Vol. 26, No. 01, marzo de 2021. Universidad Tecnológica de Pereira. ISSN 0122-1701 y ISSN-e: 2344-7214

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.

Resumen—El 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. Gómez 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 claves—Caracterización 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

Scientia et Technica Año XXVI, Vol. 26, No. 01, marzo de 2021. Universidad Tecnológica de Pereira.

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.

Scientia et Technica Año XXVI, Vol. 26, No. 01, marzo de 2021. Universidad Tecnológica de Pereira.

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.

2 3 4 5 6

Tensile Strength (MPa)

Number of layers

0.2

0.4

0.6

0.8

3 4 5

Modulus of elasticity

(GPa)

Number of layers

Scientia et Technica Año XXVI, Vol. 26, No. 01, marzo de 2021. Universidad Tecnológica de Pereira.

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.

2 3 4 5 6

Flexural stress ( MPa)

Number of layers

0.2

0.4

0.6

0.8

1.2

1.4

3 4 5

Flexural Module (GPa)

Numbers of layers

Scientia et Technica Año XXVI, Vol. 26, No. 01, marzo de 2021. Universidad Tecnológica de Pereira.

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.

Scientia et Technica Año XXVI, Vol. 26, No. 01, marzo de 2021. Universidad Tecnológica de Pereira.

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.

Scientia et Technica Año XXVI, Vol. 26, No. 01, marzo de 2021. Universidad Tecnológica de Pereira.

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 Córdoba 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 Andrés Gómez 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