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Abstract — This work addresses the effect of intermediate lamina

orientation and chemical treatment of natural fiber reinforced hybrid

composites on tensile and free vibration properties. Two different

form of fibers such as Sansevieria cylindrica (SCF) in the form of

loosely separated and coconut sheath (CS) in the form of naturally

available woven mat have been chosen for hybrid reinforcement in

polyester matrix resin. The compression molding technique was

used to fabricate the composites with the help of specially designed

mold for fiber orientation. By keeping the overall weight percentage

of hybrid composites constant (40 wt %), the long fiber SCF was

sandwiched between two CS. The hybrid composites were

fabricated the with five different intermediate lamina orientation

(i.e, 0°, 30°, 45°, 60° and 90°) using SCF. The tensile strength and

free vibration properties were analyzed for all the fabricated

composites according to the ASTM standard and impulse hammer

technique.The change in orientation of intermediate lamina have

shown significant effect on both tensile and vibration properties.

The potassium permanganate (KMnO4) chemical treatment was also

carried out for the optimum oriented angle laminate. The chemical

treatment shows the siginificant enhancement in both the properties

compared to the untreated condition.

Keywords — Sansevieria cylindrica, Coconut sheath, Orientation,

Vibration, Impulse , pottassium permanganate.

I. INTRODUCTION

Any material which is produced manually to obtain

combined advantageous properties of more than one

particular material, in and as one material and also to omit

their disadvantages is called composite materials. Thus the

composite materials are one of the greatest areas in

producing some material of desired properties by their own.

Among the composite materials, natural fiber polymercomposite materials are now attracting research peoples,

manufactures and environmentalist due to its eco-friendly

nature of the natural fiber composite materials [1-5].However, the fibre reinforced composites find its drawbacks

while using the natural fibre in polymer matrix. Owing to the

inherent weakness of the natural fibres like water absorption,

non confinement to uniformity and orientation leads to the

increase in fabrication lead time and skilled man power.

Indeed, lot of attempt has been made using natural

fibres as reinforcement with thermoset and thermoplastics

polymer resin. Saravana Bavan and Mohan Kumar [6]

describe the potential use of natural fiber composite materialsin India.As India is basically an agricultural country, the

availability of the nature fibers are much more than othercountries. Ashok Kumar et al. [7] found that the Sansevieria

cylindrica possess better mechanical properties among other

common natural fibers such as silk, jute etc. Singha et al. [8]

describes the various mechanical properties of natural fiberreinforced polymer composites. Sreenivasan et al. [9] found

the material properties of randomly oriented short sansevieria

cylindrica fiber / polyester composites. Ashok kumar et al.

[10] found the material properties of randomly oriented short

sansevieria cylindrica fiber / epoxy composites regularly

increase till 40 wt% and then with increase in wt %, the

mechanical properties tend to decline. Sreenivasan et al. [11]

studied the influence of chemical treatment of fiber on

mechanical properties of short sansevieria cylindricacomposite and found that potassium permanganate treatment

gives better enhancement of mechanical properties of composite.

At the same time the load bearing capacity of the

composites may be influenced depending upon the line of

action of the fiber orientaion [12]. Moreover, the orientation

studies [13,14]are very little in the field of hybrid composites

in particular using with two different form of natural fibers.

Hence, in this work the orientation of the loosely separated

intermediate lamina was attempted by fabrication of

sandwiched composites between coconut sheath. The

optimum fiber orientation was subjected to the KMnO4 for

surface modification to study the effect of treatment on

tensile and free vibration properties of hybrid composites.

Levengipuram, Tamilnadu, India

[email protected]

J. Winowlin Jappes

Center for Advanced Materials, Cape Institute of technology

[email protected]

[email protected], [email protected]

[email protected], [email protected]

Srivilliputtur, Tamilnadu, India

Department Of Mechanical Engineering,

Kalasalingam University

C.Bennet 1 , N. Rajini

2 , A. Venkatesh

3 , S. Harinarayana

4 , G. Vinoth Kumar

5

Center for Composite Materials,

Cylindrica Hybrid Composites

Effect of Lamina Fiber Orientation on Tensile and

Free Vibration (By Impluse Hammer Technique)

Properties of Coconut Sheath / Sansevieria

International Conference on Recent Advances in Mechanical Engineering and Interdisciplinary Developments [ICRAMID - 2014]

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II.EXPERIMENTAL

A. Material Used

The sandwiched composite is made up of using

loosely seperated Sansevieria cylindrica fiber between two

coconut sheaths with unsaturated polyester resin [6]. Methyl

Ethyl Ketone Peroxide (MEKP) and Cobalt Naphthenate

were procured from M/s Vasivibala resins (P) Ltd, Chennai,

India have been selected as catalyst and accelerator.

Sansevieria cylindrica fiber is commonly known by the name

‘snake plant’ all over the world. In southern India, it is

commonly found by the name ‘uruvanthandu’ which has

round greenish grey stripped leaves. The loosely seperated

sansevieria cylindrica fibre after extraction is shown in Fig

1(a). The sheath from the coconut tree can be easilyseparated by peeling off from the trunk of the tree and then it

is dried well and the wood dust and impurities which are

present along with them are removed and it is used directly

after cutting in to required dimension since the sheath will

reproduced automatically, there will be no physical damage

to the tree. The coconut sheath fibre in the shape of mat isshown in Fig. 1(b).

III. CHEMICAL TREATMENT

The chemical named potassium permanganate is

used for the treatment of fiber [9]. For each 100ml of water

0.5g of potassium permanganate is used. Prior to the KmnO4

treatment, NaOH alkali is used for the pre treatment of boththe fibers. For each 100ml of water, 40g of NaOH is used.

The treated fibers are dried for 1hr at 100 ºC in the hot air

woven. The treated fiber is then fabricated for the particular

orientation which has greater strength.

Fig. 1(a). Sansevieria cylindrica after extraction

Fig. 1(b). Coconut Sheath

IV. TENSILE PROPERTIES

Tensile test is conducted to find the tensile

strength of the fabricated composites in (Instron, Series-

3382) a UTM. The cross head speed of 5 mm/min is

maintained according to the ASTM D:638-10. The size of

the specimen is 200x20x3mm.

V. V IBRATION TESTING

The vibration test is done to find the damping ratioand natural frequency of the composite. Impulse hammer

method was followed for finding ratio and frequency. The

one end of the specimen is fixed in the clamping block,

similar to a cantilever beam. The other end is to be free and

the sensor is fixed on the top of the specimen. Free vibration

method is followed. Three hits are made on the specimen, one

near to the clamping block, second hit is at the middle of the

specimen and the last is near to the sensor. The vibration

signals are monitored and the damping ratio and natural

frequency are calculated. The ASTM D 638 was followed forthis specimen. The size of the specimen is 200*13*3mm.

The line diagram of the free vibration testing set up is

shown Fig.2.

VI. FABRICATION OF HYBRID COMPOSITES

Hybrid composites are prepared by the compression

moulding technique. The coconut sheath are placed in the topand bottom lamina, while the sansevieria is placed in the

middle lamina. The arrangement of fiber in three lamina's are

described in the Fig. 3(a-c) and the mould used for

fabrication are shown below.

Fig. 2. Free Vibration Testing Setup

Fig. 3 (a). Outer and interlamina fibre arrangement


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Fig. 3 (b). Mold used for interlamina orientation

VII. RESULT AND DISCUSSION

A. Tensile Properties of Untreated hybrid composites

The investigation of tensile strength of the various

specimen on different fiber orientations were done. The

various orientation's 0, 30, 45, 60, 90 degrees are symbolized

in the x-axis by the point number 1 to 5. The outcome of the

testing states that the point 1 that is the fiber orientation at 00

has got the supreme strength of 71.3 Mpa., when comparedto the other type of fiber orientation. The point 5 that is 900

fiber orientation has the least strength of 11.54 Mpa. While

studying the tensile testing in the 00

middle lamina fiber

orientation, it exhibit that the fiber in the middle lamina are

assembled parallel to the force applied. When the force

applied for this type, the force is carried by both the fiber and

the resins. This is the reason why that the hybrid composite

in the 00 orientation explore an higher strength. Meanwhile

analyzing the result of 900 degree middle lamina fiber

orientation, that the fiber's are assembled perpendicular to

the force applied.In this condition when the force is appliedto the hybrid composite, the force will act on the resins and

does not act much on the fiber. So the middle lamina fiber

orientation on 900

exhibit the lesser strength. The tensile

strength of different orientation are plotted in the graph given

in Fig.4(a).

B. KMnO4 Treated Composites

The hybrid composite with treated fiber is fabricated

and the testing is done on the specimen and the results are

analyzed. The point 1 in the x-axis represent the un-treated

hybrid composites, while point 2 represent the treated hybridcomposites. As we analyze the tensile strength has been

reduced from 71.3 (Mpa) to 66.38 (Mpa) after the fiber

treatment. The strength has been declined by 7.5% after the

treatment of the fiber. The graph has been shown in the

Fig.5(a).

C. Free vibration Test of Untreated Hybrid Composites

Free vibration testing was done for the specimens.

The different orientation such as 0, 30, 45, 60& 90 are

represented by the point no. 1 to 5 in the x-axis. Analyzing

the graph shown in the figure no. 8, 9& 10 state that the

damping ratio at the point 2 that is 300

orientation has thegreater value of 0.49, 0.3927& 0.0152 for the node 1, 2 & 3

respectively. In mode 1 point 4 has got the lowest damping

ratio with the value of 0.2678. Table 2 shown the natural

frequency of specimens. While in the mode 2 shown in table

2 point 5 (i.e 900) has got the lesser value of 0.023 and in the

mode 3 that is in the Fig. 6 point 1 (ie 450) has got the lesser

value of 0.01233. While analyzing the natural frequency of

the different mode it state that in mode 1 has the natural

frequency has 17.09 Hz at point 4 and in mode 2 and 3 thenatural frequency has 84.23 and 272.23 Hz respectively. In

the same way the lesser frequency exhibits in point 2 of all 3

modes with frequency value of 1.22, 17.09 & 84.23

respectively.

D. Free Vibration Test of Untreated Hybrid Composites

Free vibration testing was done for the specimens.The different orientation such as 0, 30, 45, 60& 90 are

represented by the point no. 1 to 5 in the x-axis. By the

analyzing of the graph shown in the figure no. 8, 9& 10 are

state that the damping ratio at the point 2 that is 300

orientation has the greater value of 0.49, 0.3927& 0.0152 for

the node 1, 2 & 3 respectively. In mode 1 point 4 has got the

lowest damping ratio with the value of 0.2678. Table 2

shown the natural frequency of specimens. While in the

mode 2 shown in table 2 point 5 (i.e 900) has got the lesser

value of 0.023 and in the mode 3 that is in the Fig. 6 point 1(ie 450) has got the lesser value of 0.01233. While analyzing

the natural frequency of the different mode it state that in

mode 1 has the natural frequency has 17.09 Hz at point 4 and

in mode 2 and 3 the natural frequency has 84.23 and 272.23

Hz respectively. In the same way the lesser frequency

exhibits in point 2 of all 3 modes with frequency value of 1.22, 17.09 & 84.23 respectively.

Fig. 4 (a). Tensile properties of untreated SC/CS/polyester hybrid

composites Tensile strength

Fig. 4 (b). Tensile properties of untreated SC/CS/polyester hybrid

composites Tensile Modulus


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Fig. 5 (a). Tensile Properties of Untreated and KMnO4 treated hybridoptimum composites Tensile strength

Fig. 5 (b). Tensile Properties of Untreated and KMnO4 treated hybrid

optimum composites Tensile Modulus

Table I. Fundamental Natural frequencies and Damping of hybrid

composites at Different Orientation (a) Mode - I (b) Mode – II

(c) Mode – III

Orientation Natural Frequency Damping Ratio

Mode

1

Mode

2

Mode

3

Mode

1

Mode

2 Mode 3

0 15.87 84.23 272.22 0.0769 0.0399 0.01233

30 1.22 17.09 84.23 0.49 0.3927 0.0152

45 8.55 46.5 84.23 0.066 0.295 0.0499

60 17.09 80 93.4 0.2678 0.019 0.1027

90 15.87 76.9 84.23 0.0563 0.023 0.1065

Treated 26.86 84.23 272.83 0.456 0.0145 0.0045

E. KMnO4 Treated Composites

The treatment of fiber in done and fabrication of

fiber is done only for the 00

orientation, the reason is that the

orientation of 00

degree has the greater strength for all themechanical properties. In analyzing the result of the treated

hybrid composite with the untreated hybrid composite the

following are found. The Figures from 7a-c state the

damping ratio of the 3 different modes and the figure

numbered from 18 to 20 state the natural frequency in Hz of

the 3 different modes. On analyzing the damping ratio, theratio has increased by 83% from 0.0769 to 0.456 in the mode

1, while in the other modes the ratio has decreased to 63%.

In the case of natural frequency the mode shows the

increment in the value of 40% from 15.87 to 26.86 Hz. In

other two cases the frequency value remains the same.

Table.II. Comparison of Natural Frequency and Damping ratio of untreatedand KMnO4 treated optimum composites

Orientation Natural Frequency Damping Ratio

Mode

1

Mode

2

Mode

3

Mode

1

Mode

2 Mode 3

Untreated 15.87 84.23 272.22 0.0769 0.0399 0.01233

Treated 26.86 84.23 272.83 0.456 0.0145 0.0045

VIII. CONCLUSION

Sansevieria Cylindrica and coconut sheath hybrid

composites are prepared by compression moulding

machine.The hybrid composites were subjected to tensile and

vibration analysis (damping ratio and natural frequency).Itwas observed that enhanced tensile properties were observed

for 00

fibre orientation in case of untreated and treated

composites. The middle lamina fiber orientation at 900

exhibit the lesser strength. Vibration analysis were done for

treated composites with potassium permanganate solutiononly for 0

0fibre orientation as they showed higher tensile

properties than any other fibre orientations.Treated

composites exhibited higher natural frequency for all the

three modes of vibration. Damping ratio is higher for treated

composites for mode 1(the ratio has increased by 83% )

which proves to be advantageous one.

ACKNOWLEDGEMENT

The authors thank the centre for composite

materials, Kalasalingam university, Krishnankoil for

providing assistance to carry out this work.

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