Effect of Natural Sisal Fiber Reinforcement on the …polymer composites, then it is called natural fiber polymer composite. Muhannad Al-Waily University of Kufa, Faculty of Engineering,

International Journal of Mechanical & Mechatronics Engineering IJMME-IJENS Vol:17 No:01 30

N SI J E IJENS February 2017IJENS © -IJMME-4848-170601

Effect of Natural Sisal Fiber Reinforcement on the

Composite Plate Buckling Behavior Muhannad Al-Waily, Alaa Abdulzahra Deli, Aziz Darweesh Al-Mawash, Zaman Abud Almalik Abud Ali

Abstract— Buckling behavior of composite plate taking into

account the effect of natural sisal fiber reinforcement is

presented in this work. Investigating the buckling load of

composite plate was done using both experimental and

theoretical (including analytical and numerical) techniques. The

composite plate specimens examined was reinforced with various

volume fractions of natural sisal fiber. Furthermore, the

composite plate was supported with different boundary

conditions. The experimental and analytical data obtained for the

buckling load are further supported with numerical data

evaluated using the finite element method by ANSYS 14.0

commercial code. In the experimental method, the samples of the

tensile test composite as well as the buckling plate are firstly

manufactured. Then, the modulus of elasticity for the samples of

composite plate with tensile test was evaluated, while the

buckling load of plate was evaluated by the buckling test of

composite plate. The results of buckling plate reveal that the

reinforcement of natural sisal fibers leads to increasing the plate

stiffness, and hence, causes an increase in the buckling load of

composite plate. Moreover, a comparison was conducted between

the data obtained for the buckling load, where a good agreement

was found. The maximum error found between the results

obtained experimentally and those estimated theoretically was

about (12.28%), while it was about (3.9%) between the analytical

and numerical predictions.

Index Term-- Buckling Plate, Sisal Fiber Reinforcement,

ANSYS Program Buckling, experimental buckling, composite

plate buckling, composite material plate, composite buckling.

I. INTRODUCTION

Natural fibers are usually classified as plant, animal and

mineral fibers. The plant fibers include many types, which are

seed fiber, stalk fiber, Leaf fiber, fruit fiber, stem and Tracheid

(Wood (Softwood & Hardwood)). The natural fibers have a

significant role in the industry field and contribute

considerably in reducing the production cost, especially the

consumables, [1].

When fibers obtained from plant origin or some other living

species, i.e. natural fibers, are used as reinforcement in

polymer composites, then it is called natural fiber polymer

composite.

Muhannad Al-Waily University of Kufa, Faculty of Engineering, Mechanical Engineering

department, Iraq, [email protected]

Alaa Abdulzahra Deli University of Kufa, Faculty of Engineering, Mechanical Engineering


Aziz Darweesh Al-Mawash University of Kufa, Faculty of Engineering, Mechanical Engineering


Zaman Abud Almalik Abud Ali University of Kufa, Faculty of Engineering, Mechanical Engineering


The major factors affecting the structure as well as chemical

composition of plant fibers are the environmental conditions

and its age. The primary ingredient of any plant fiber is water.

However, if considered on dry basis, all natural fibers consist

of cellulose and hemicellulose combined with lignin along

with small amount of starch, proteins and other extractives

which are distributed all over the cell wall.

The effect of sisal reinforcement fiber on composite plate

behavior has gained increasing interest recently. An

experimental and numerical study was presented by Zaman

[2] regarding the preparation of composite material specimen

using natural fibers sisal and polyester resin. The specimens

were pretreated in different volume fractions of sisal and

resins, which were (5-35) % sisal. Specimen model was

fabricated in a plate shape, where vibration and tensile tests

were applied. Natural frequency was obtained through

numerical analysis using ANSYS 14.0 commercial code. A

similarity was observed between the experimental and

numerical data obtained. The findings obtained reveal that

increasing the volume fraction of sisal fibers results in

improving the dynamic behavior of the plate tested. The

mechanical and thermal properties of composite materials

with silica reinforcement effect were examined by Gowthami

et al. [3]. The mechanical properties studied were the strength

and modulus of elasticity of composite materials with silica

reinforcement. In addition, influence of thermal properties of

composite materials, taking silica effect into account, was

studied, e.g. specific heat. It was also shown that using silica

reinforcement in the composite materials improves the

mechanical properties significantly. The impact of fiber

orientation on mechanical properties of sisal fiber reinforced

composites was experimentally studied by Kumaresan et al.

[4]. Sisal fiber was used as a reinforcement, which is treated

with NaOH solution to enhance the bonding strength between

fiber and resin. Samples having various orientations of sisal

fiber were firstly fabricated by compression molding, and then

their mechanical properties, i.e. tensile strength and flexural

strength, were investigated. Romildo et al. [5] presented a

study for the effect of sisal fiber reinforcement on the tensile,

compression, and bending behaviors in addition to the creep

and other properties of composite materials. It was noticed

that the sisal fiber reinforcement improves the properties of

composite materials; hence, sisal fiber reinforcement

composite materials can be utilized efficiently in civil

construction. Kumar et al. [6] conducted an experimental

vibration analysis of composite laminate taking into account

the effect of different natural reinforcement fiber. The

reinforcement natural fibers tested were the short sisal and

banana reinforcement fibers. The composite materials

examined was combined form random short reinforcement

mailto:[email protected]





sisal or banana fiber and polyester resin materials. The results

concluded indicate that the mechanical properties and

vibration of composite laminate is improved with increasing

the reinforcement of natural fibers. Oladele et al [7]

investigated the effects of production processes on the

mechanical properties of sisal fiber reinforced polypropylene

(PP) composites. The sisal fiber used for the reinforcement

was extracted by soil retting, and then chemically treated.

Both treated and untreated sisal fiber were characterized and

used for the reinforcement of homopolymer and copolymer

polypropylene. The composites were produced by

compression molding technique after which mechanical tests

such as tensile, impact and hardness tests were carried out on

the samples. The results showed that soil retting is efficient for

the extraction of sisal fiber and that chemical treatment can be

used to enhance the properties of the fiber as well as the

mechanical properties of the composites produced.

The above mentioned researches examined thoroughly the

mechanical properties and vibration behavior of sisal

reinforcement effect. However, the impact of sisal fiber

reinforcement on the buckling behavior of composite

structures has not been investigated before. Thus, the current

work aims to experimentally and numerically study the

influence of sisal reinforcement on the buckling behavior of

composite plate with different supports. It is also aimed to

investigate the buckling load analytically for simply supported

plate with sisal reinforcement. Also, the mechanical properties

of composite materials plate is planned to be studied

analytically and experimentally.

II. EXPERIMENTAL INVESTIGATION

The experimental study includes estimation of the mechanical

properties of composite materials that consist of polyester

resin materials, which is reinforced with sisal natural fiber.

Then, the buckling load of composite plate is measured for

various sisal volume fractions and boundary conditions. The

manufacture of composite tensile test sample and buckling

plate sample includes mixing the polyester resin materials

with the sisal natural fiber inside mineral mold. Later, pressure

is applied on the samples using hydraulic jack, as illustrated in

Fig. 1. The mechanical properties of composite materials is

determined for five samples of fiber volume fractions as

shown in Figs. 2 and 3 for longitudinal and transverse

directions; so, the mechanical properties for each volume

fraction is evaluated for five samples depending on the

average value for each ratio as in Fig. 4.

The samples used in tensile test of orthotropic composite

materials, are shown in Figs. (5-a) & (5-b) for longitudinal and

transverse directions, are taken from the ASTM (D 3039 M-

E122) [8]. The tensile test is accomplished using the universal

machine to get results illustrated in Fig. 6.

The five tensile samples for each volume fraction are

evaluated by dividing the sample made for each volume

fraction with dimensions detailed below, as given in Fig. 7:

1. The length of composite tensile sample .

2. The width of composite tensile sample .

3. The thickness of composite tensile sample .

Fig. 1. Block to manufacture the composite plate structure.

Fig. 2. Modulus of elasticity in longitudinal direction of composite materials.

Fig. 3. Modulus of elasticity in transverse direction of composite materials.

Fig. 4. Experimental Modulus of Elasticity for Different Sisal Volume

Fraction Reinforcement of composite Materials.



a. Longitudinal direction fiber.

b. Transverse direction fiber.

Fig. 5. Longitudinal and transverse tensile test samples.

Fig. 6. Universal tensile test machine.

The weight required for tensile sample for each volume

fraction are shown in Table I, which are calculated as,

(1)

Where

, [2], and

are volume fractions of sisal fiber and

polyester resin materials, respectively.

Moreover, the tensile sample is divided into five tensile test

samples with the dimensions below, [9, 10]:

1. The length of composite tensile sample .

2. The width of composite tensile sample .

3. The thickness of composite tensile sample .

(a) Longitudinal tensile samples.

(b) Transverse tensile samples.

Fig. 7. Divided of longitudinal and transverse tensile samples.

Longitudinal tensile plate sample

𝑆𝑙1

𝑆𝑙2

𝑆𝑙3

𝑆𝑙4

𝑆𝑙5

Fiber direction

𝑆𝑡1

𝑆𝑡2

𝑆𝑡3

𝑆𝑡4

𝑆𝑡5

Transverse tensile plate sample

Fiber direction



Table I

Required weight for sisal and polyester resin of tensile test composite sample

Sample (%)

(%)

Weight of

fiber (g)

Weight of

resin (g)

1 0 100 0 220

2 10 90 28 198

3 20 80 56 176

4 30 70 84 154

5 40 60 112 132

In the second part of experimental work, the sample's buckling

load of composite plate were evaluated, as seen in the Fig. 8,

for different fiber volume fractions with two boundary

conditions as:

1. Two edges free and other two edges fixed supported

(CCFF).

2. Two edges free and other two edges simply supported

(SSFF).

The dimensions of composite plate sample are,

1. The length of composite plate sample .

2. The width of composite plate sample .

3. The thickness of composite plate sample .

Also, the weight of fiber reinforcement and polyester resin

materials required to made buckling plate sample are shown in

Table II, where the required weight can be calculated as,

(2)

Table II

Required weight for sisal and polyester of vibration plate composite samples

Sample (%)

(%)

Weight of

fiber (g)

Weight of

resin (g)

1 0 100 0 132

2 10 90 16.8 118.8

3 20 80 33.6 105.6

4 30 70 50.4 92.4

5 40 60 67.2 79.2

Fig. 8. Vibration sample of composite plate with sisal reinforcement.

The buckling load of each volume fraction ratio is evaluated

for four samples, as shown in Figs. 9 and 10, and then, the

average value of each samples is estimated, as explained in

Fig. 11 for various boundary conditions as,

1. Simply supported for two edges (at sides) and free

supported for other two edges (at sides) (SSFF), Fig.

12.a.

2. Clamped supported for two edges (at sides) and free

supported for other two edges (at sides) (CCFF), Fig.

12.b.

Another measurement of the buckling load was done by

conducting compression between the composite plate samples

after supporting the plate in the universal tensile machine with

compression parte, as displayed in Fig. 13. Then, the lateral

displacement of composite plate is recorded depending on the

(dial gauge) from both sides, surrounding the value of

buckling load when the (dial gauge) begins to read the

deflection of composite plate, as demonstrated in Fig. 14.

Alternatively, the buckling load can be measured by locating

the point where the compression curve changes from linear to

another trend, which is known as the buckling load, [11], as

indicated in Fig. 15.

Later on, from Figs. 4 and 11, it can be observed that

increasing the sisal reinforcement causes an enhancement in

the composite materials strength and modulus of elasticity in

directions 1 and 2. Therefore, increasing the sisal

reinforcement augments the buckling load of composite plate

with CCFF and SSFF supported plate. Also, Fig. 11, shows

that the buckling load of CCFF supported plated is more than

it is for the SSFF supported plate since the stiffness of the

latest is greater than the stiffness of the SSFF supported

composite plate.

Fig 9. Experimental buckling load for four samples of each volume fraction of

sisal reinforcement for SSFF plate boundary.

Fig. 10. Experimental buckling load for four samples of each volume fraction

of sisal reinforcement for CCFF plate boundary.

𝑤𝑏

𝑙𝑏



Fig. 11. Experimental buckling load for different sisal volume fraction and

various boundary condition of composite plate.

(a) SSFF plate supported.

(b) CCFF plate supported.

Fig. 12. Supported of composite plate samples.

Fig. 13. Buckling load machine.

Fig. 14. Buckling plate sample.

Fig. 15. Compression load- displacement relation.

III. ANALYTICAL INVESTIGATION

The analytical part of the present work includes evaluating the

mechanical properties and critical buckling load of simply

supported plate with different fiber volume fractions. Also, the

theoretical results were compared with the numerically

computed data, where an excellent good agreement was found.

The results obtained analytically for the modulus of elasticity

were also compared with the experimentally measured data.

The equation can be used to evaluate the critical buckling load

for orthotropic composite plate is [12],

( )

(1)

Where w is the deflection of plate in z-direction.

Then, by solving Eq. 1 for simply supported plate with

substituting

(for are length and

width of plate, respectively) into Eq. 1, and then using

orthogonally method; a general equation for the buckling load

(N/m) of simply supported plate is derived as,

2√ 11 22

2[√

11

22(

)

( 12 66)

√ 11 22 √

22

11( 2

)

]

(2)

𝑤𝑏

𝑙𝑏

𝑆 𝑆

𝐹

𝐹

𝑤𝑏

𝑙𝑏

𝐶 𝐶

𝐹

𝐹

Output read load

Composite buckling

plate sample

Dial gage

Move supported

Buck

lin

g p

late

D

ial

gage

Sup

po

rted

of

pla

te p

arts



Where 1

3

( 12 21) ,

2 3

( 12 21) ,

2

3

( 12 21) ,

12 3

While are the moduli of elasticity of composite

plate in 1 and 2-direction, respectively. Also, is the

Passion’s ratio of composite plate in 1,2-direction, stands

for the modulus of rigidity in 1,2-direction of plate, and h

represents the thickness of plate (can be used ).

Apparently, the above equation requires the mechanical

properties of the composite material investigated. Therefore,

the mechanical properties for both the sisal reinforcement

fiber and polyester resin materials are evaluated provided

separately, i.e. modulus of elasticity, modulus of rigidity, and

Poisson’s ratio. Thus, the Poisson's ratio and modulus of

elasticity for sisal fibers are respectively , [7], while the corresponding values for the resin

polyester are , [8], respectively.

Eventually, the modulus of rigidity for sisal and polyester

materials can be evaluated as,

( ) , so,

, (3)

Where, G: shear modulus, E: Modulus elasticity, ν: Poisson

ratio; while the Poisson ratio of composite material specimen

can be found using the equation below [9],

(4)

Where, : Volume fraction of fibres, : Poison’s

ratio of fibres, : Volume fraction of polyester, and

: Poisson’s ratio of polyester

The shear modulus of composite material can be found using

equation below: [9],

(5)

Also, the modulus of elasticity in longitudinal and transverse

directions can be evaluated by, [13],

( ) (6)

Thus, the theoretically calculated mechanical properties of

composite materials required for evaluating the buckling load

of simply supported composite plate using equation Eq. 2 are

listed in Table III.

Table III

Theoretical input data of mechanical properties required.

Sample ( )

( )

( )

1 100 0 4 4 1.43 0.4

2 90 10 4.65 4.26 1.53 0.392

3 80 20 5.3 4.57 1.64 0.384

4 70 30 5.95 4.91 1.77 0.376

5 60 40 6.6 5.32 1.92 0.368

Then, the experimentally estimated mechanical properties

given in Fig. 4 were compared with the theoretical data

presented in table 3, as illustrated in Figs. 16 and 17 where a

good agreement has been observed with maximum error about

(9.8%).

The analytical solution derived for the simply supported

composite plate (compound of the unidirectional fiber and

resin materials) using the general equation of buckling load,

i.e. Eq. 2. The analytical data obtained from this equation are

illustrated in Fig. 18 for the relation between the buckling load

and sisal reinforcement volume fraction. It is clear that the

buckling load is enhanced with increasing the fiber sisal due to

augmentation in the modulus of elasticity of composite

materials. Also, it is noticed that the buckling load of simply

supported plate is more than it is for other supported plates

presented in the experimental work.

Fig. 16. Comparison between experimental and theoretical work for modulus

of elasticity in longitudinal direction composite materials.

Fig. 17. Comparison between experimental and theoretical work for modulus

of elasticity in transverse direction composite materials.

Fig. 18. Buckling load of simply supported composite plate with various sisal

volume fraction.

IV. NUMERICAL INVESTIGATION

The finite element method is used to numerically determine

the buckling load of composite plate, where the well-known

commercial code ANSYS 14.0 is employed. The element type

used to determine the buckling load is Shell 281 because it can



be used to layer the applications for composite shell or

sandwich construction modeling. Besides, this element is

suitable for analyzing thin shell to moderately-thick shell

structures. In addition, the element is suitable for linear, large

rotation and/or large strain nonlinear applications. The

element has eight nodes with six degrees of freedom at each

node: translations in the x, y, and z axes, and rotations about

the x, y, and z axes. The geometry and nodes of the element

type Shell 281 are shown in Fig. 19, [13].

Fig. 19. Geometry and Nodes of Sell 281.

In order to compare the numerical results with the

experimental results, data are required for filling out the fields

of ANSYS. These data (E1 and E2) can be extracting from

tensile test as shown in Fig. 4. Other data (shear modulus and

Poisson's ratio) are estimated from theoretical equations (eqs.

3-5). The mechanical properties, mentioned above, are listed

in table IV, and used to evaluate the buckling load using

Ansys program for the experimental and numerical

comparisons.

Table IV

Experimental and theoretical input mechanical properties required for Ansys.

Sample ( )

( )

( )

1 100 0 3.75 3.75 1.43 0.4

2 90 10 4.38 3.84 1.53 0.392

3 80 20 5.18 4.25 1.64 0.384

4 70 30 5.53 4.53 1.77 0.376

5 60 40 6.03 4.96 1.92 0.368

Similarly, for the comparison of the analytical and numerical

results of the bucking load, mechanical properties are required

to be used in ANSYS. These properties (modulus of elasticity

E1, E2, shear modulus G12 and Poisson's ratio ) can be

extracting from analytical equations (eqs. 3-6), as listed in

Table III.

Figs. 20 and 21, present the comparison between the

experimental and numerical works of the buckling load of

SSFF and CCFF composite plate. Good agreements with

maximum error about (12.6%) were shown in there figures.

Also, Fig. 22 shows the comparison between the analytical

and numerical results of simply supported composite plate for

various sisal volume fractions. Good agreement with

maximum error about (3.9%) was also shown in Fig. 22.

Then, the comparison of the buckling load with different

boundary condition of plate can be shown in Fig. 23, where

Fig. 23 shown the numerical results for buckling load with

various fiber volume fraction for different plate boundary

condition as (SSSS, SSFF, CCFF), and then, the figure shown

that the buckling load of simply supported plate greater than

buckling load for other supported plate. Since, the fixed and

stiffness of simply supported greater than for other supported.

Fig. 20. Comparison between experimental and numerical buckling load

results of SSFF plate.

Fig. 21. Comparison between experimental and numerical buckling load

results of CCFF plate.

Fig. 22. Comparison between theoretical and numerical buckling load results

of SSSS plate.



Fig. 23. Numerical buckling load for different sisal volume fraction and

various boundary condition of composite plate.

V. CONCLUSION

From the results discussed earlier regarding the mechanical

properties and buckling load obtained experimentally and

theoretically along with the comparison of the results found

with the numerically computed data, the following remarks

can be concluded,

1. The comparison between experimental and numerical

results showed a good agreement with maximum error

about (12.6%). Hence, the experimental work is a powerful

technique to evaluate the buckling load of composite plate.

2. As the comparison between the theoretical and numerical

results showed a good agreement with maximum error

about (3.9%), the theoretical work can be considered as a

powerful technique to evaluate the buckling load of simply

supported composite plate.

3. The sisal reinforcement fiber causes an increase in the

strength of composite materials; hence, increasing the

volume fraction of sisal reinforcement fiber improves the

modulus of elasticity (mechanical properties of composite

materials).

4. Increasing the volume fraction of reinforcement fiber

causes an enhancement in the composite materials

strength, thus, increasing the sisal reinforcements leads to

improving the buckling load of composite plate with

different boundary conditions.

5. Fixing the plate from all sides causes an increase in the

plate strength; therefore, the buckling load of composite

plate is enhanced. Thus, the buckling load of SSSS is

greater than it is for both the SSFF and CCFF. Also, the

buckling load of CCFF plate is greater than it is for the

SSFF composite plate.

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Effect of Natural Sisal Fiber Reinforcement on the …polymer composites, then it is called natural fiber polymer composite. Muhannad Al-Waily University of Kufa, Faculty of Engineering,

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