Procedia Engineering 97 ( 2014 ) 687 – 693

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1877-7058 © 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).Selection and peer-review under responsibility of the Organizing Committee of GCMM 2014doi: 10.1016/j.proeng.2014.12.298

ScienceDirect

12th GLOBAL CONGRESS ON MANUFACTURING AND MANAGEMENT, GCMM 2014

Free Vibration Characteristics of Phoenix Sp Fiber Reinforced Polymer Matrix Composite Beams

G.Rajeshkumar*, V.Hariharan, Department of Mechanical Engineering, Kongu Engineering College, Erode, Tamilnadu, India

Abstract

In recent days the use of natural fiber reinforced polymer composites in automobile, aerospace and other industrial applications becomes increased due to light weight, less cost, bio degradability and easy to manufacture. It becomes necessary to know the dynamic behavior of natural fiber reinforced composites to use it effectively for engineering applications. This paper presents the free vibration characteristics of newly identified Phoenix Sp fiber reinforced polymer matrix composite beams, moreover the physical, chemical and mechanical properties of fiber was determined by using standard experimental methods. The modal analysis is carried out on composite beams having different fiber gauge lengths such as 10mm, 20mm, 30mm, 40mm and 50mm. The Clamped-Free (CF) boundary condition is used for the analysis. The composite beam with 30mm fiber length has maximum natural frequency with less amplitude; hence it is suggested for industrial applications. © 2014 The Authors. Published by Elsevier Ltd. Selection and peer-review under responsibility of the Organizing Committee of GCMM 2014.

Keywords: Phoenix Sp fiber; Free vibration; Composite beams; Boundary condition.

1. Introduction

Many industrial sectors concentrate on the manufacturing of natural fibers based products because of their special characteristics to produce industrial components, automotive parts, aerospace and domestic applications. These natural fibers are available in plant stems, leaves, seeds and fruits. These fibers are extracted by manual peeling or by using machines. The extraction method for vakka, date and bamboo fibers is studied by Murali et al. [1]. The vakka fiber is extracted from its sheath after 18-25 days of immersion in water retting tank. Moreover the date and bamboo fibers are extracted by manually and decorticating followed by chemical process respectively. Boopathi et al. [2] determined the physical, chemical and mechanical properties of raw and alkali treated borassus fruit fiber experimentally. Reddy and Yang [3] investigated the chemical, morphological and tensile properties of ______________ * Corresponding author. Tel.: +0-04294-226714; fax: +0-04294-220087

E-mail address: grk.kongu@gmail.com

© 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).Selection and peer-review under responsibility of the Organizing Committee of GCMM 2014

688 G. Rajeshkumar and V. Hariharan / Procedia Engineering 97 ( 2014 ) 687 – 693

natural cellulose hop stem fiber. The chemical compositions like lignin, ash and cellulose contents were determined according to ASTM D1106-96, ASTM E1755-01 and AOAC 973.18 respectively. The Young’s modulus, breaking tenacity and elongation at break was obtained using Instron tensile tester. Saravanakumar et al. [4] have compared the chemical, mechanical and thermal properties of prosopis juliflora bark fiber with the other known natural bark fibers. Sathishkumar et al.[5] investigated the physical, chemical, mechanical and thermal properties of newly identified sanservieria ehrenbergii. This fiber was extracted from plant leaves by using mechanical, chemical and water retting processes. Fidelis et al. [6] investigated the effect of fiber morphology on the tensile strength of jute, sisal, curaua, coir and pissava fibers obtained from Brazil region. The jute fiber was extracted by following the sequence of steps like cutting, retting, shredding, drying and packing. The sisal and curaua fibers were extracted their respective leaves by mechanical decortication. Moreover the pissava and coir fibers are extracted from petiole of leaves and coir shell respectively. Defoirdt et al. [7] assessed the tensile properties of coir, bamboo and jute fibers by assuming that the cross section of the fibers was uniform. Rajini et al. [8] determines the influence of nano-clay addition and chemical modification of coconut sheath on natural frequencies and mode shapes.

Senthilkumar et al. [9] addresses the free vibration characteristics of SFPC and BFPC polyester composites. The

influence of fiber length and weight percentage on mechanical properties and free vibration characteristics was addressed. The dimensions of beam used for the analysis is 200mm x 20mm x 3mm. The impact hammer of Kistler model 9722A500 and accelerometer is used for testing. The signals from the accelerometer were recorded in computer using DAS. Rajini et al. [10] developed the naturally woven coconut sheath/E-glass chopped strand mat fiber reinforced hybrid composites and investigate its mechanical and free vibration characteristics. The tensile, flexural and impact properties were conducted according to ASTM-D638, ASTM-D790 and ASTM-D256 methods respectively. The accelerometer (Kistler model 8778A500) and modally tuned impact hammer (Kistler model 9722A500) are used for the investigation. The results revealed that the increase in mechanical and damping behaviour of coconut sheath/coconut sheath/E-glass hybrid composite can be used as a replacement for pure glass fibers. DeValve and Pitchumani [11] presented a numerical model describing the vibration damping effects CNT’s embedded in the matrix of fiber reinforced rotating composite structures.

Cui Yanbin et al. [12] created the finite element model of turbine blade and obtain the modal parameters and natural frequency of the turbine blade in ANSYS software using laminated shell element. Calim [13] used numerical procedure to analyze the free and forced vibrations of different cross section composite beams with various boundary conditions and the effects of fiber orientation angles on dynamic behavior of composite beams are also investigated. In the present study, the newly identified Phoenix Sp fibers are extracted manually from the leaf stem of phoenix sp plants. The physical and chemical properties of the raw fibers are investigated. In addition, the modal analysis was carried out on the composite beams reinforced with this fiber to determine its vibration characteristics

Nomenclature

SFPC Sisal fiber polyester composites BFPC Banana fiber polyester composites CNT’s Carbon nanotubes CF Clamped-Free DAS Data Acquisition System

2. Experimental details

2.1. Materials

A Phoenix Sp plant was identified in Coimbatore region, Tamilnadu, South India is shown in Fig 1(a). This plant leaf stem has fibres throughout its thickness. This plant yields 35 to 42 leaf stems per year. The length of the leaf stems varies from 2.5 feet to 5 feet. The leaves present in the stem were removed by using sharp knife, and the stems are cut down to the required length and immersed in water retting tank for about 20 days is shown in Fig 1(b) & (c). During this water retting process the gum like materials are removed from the leaf stems. Then the single

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fibers are extracted by manual peeling (Fig. 1d) and washed with running water for the removal of unwanted materials present over the surface of the fiber. Finally, the fibers are dried at room temperature for 2 days.

Fig. 1. Phoenix Sp fiber (a) Plant, (b) Leaf stem, (c) Water retting, and (d) Manual peeling

2.2. Fabrication of composites

The composites were prepared by using compression molding in a steel die of 250 mm x 200 mm x 3 mm. Initially the polishing wax is applied at inner surface of the die. Then the chopped fibers are arranged randomly in the mold. The isophthallic polyester resin is used for the investigation, which is mixed with an accelerator (Methyl Ethyl Ketone Peroxide) and catalyst (Cobalt Naphthalene). The accelerator and catalyst are used to cure the resin at faster rate. The resin is poured onto the mold and then it is closed and compressed using hydraulic press, allowed curing for 24 hours at room temperature. The composites are prepared by varying the fiber length of 10 mm, 20 mm, 30 mm, 40 mm and 50 mm. The weight fraction of the fiber is maintained as 10% throughout the analysis.

2.3. Properties of Phoenix Sp fiber

The Phoenix Sp fiber is a newly identified one; hence it is required to determine the properties of this fiber. The density of fiber was determined by using Archimedes method according to ASTM D 3800-9 [15]. The diameter of the fiber was determined by using an image analyser. The wax and lignin contents present in the fiber was determined by using Soxhlet apparatus and APPITA P11s-78 method respectively [16]. The moisture and ash contents are obtained by weight loss method. The tensile strength of phoenix sp fiber with 20 mm, 30 mm, 40 mm, 50 mm and 60 mm gauge length was determined according to ASTM D 3822-01 [16, 17]. 25 samples of fibers in each gauge length were tested using INSTRON 5500 R universal tensile testing machine at 65±1.5% relative humidity and temperature of 21±1.5ºC with a cross head speed of 10 mm/min. A load cell of 1.0 kN was used to measure the load.

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2.4. Modal analysis

Modal analysis is used to obtain the natural frequencies and mode shapes for the structures. Fig.2 shows the experimental setup used to carry out the free vibration analysis of Phoenix Sp fiber reinforced polyester composite beams of size 250 mm x 25 mm x 3 mm. The different gauge length of fibers like 10mm, 20mm, 30mm, 40mm and 50mm was used to prepare the composite beams.

Fig. 2. Experimental setup for free vibration test.

In Natural fiber reinforced composites, the natural frequency depends on many factors such as fiber length, orientation and fiber/matrix interface [9]. The cantilever composite structure was applied with a force to one corner of the plate. Force was applied at five different places in composite beams with the help of impact hammer (Kistler model 9722A500). The response of the composite beams was measured with an accelerometer (Kistler model 8778A500) attached to one corner of the plate using wax. The most important measurement needed for experimental modal analysis is the frequency response function, i.e. the ratio between output response and input excitation force. This measurement is typically acquired using a FFT (Fast Fourier Transform) analyser. Finally the signals are stored in the personal computer.

3. Results and discussion

3.1. Properties of Phoenix Sp fiber

The diameter of the Phoenix Sp fiber was obtained by measuring the length L1 in fiber image taken through image analyzer as shown in the Fig 3(a). Moreover the diameter of fiber is not uniform which depends on environmental conditions in which the plant grows, hence the diameter of 30 samples was taken and average value is noted as 0.5766 mm. The distribution of fiber among different samples is shown in Fig. 3(b). The density of Phoenix Sp fiber was obtained as 1.2576g/cc using Archimedes method. The organic materials like cellulose, lignin and other properties like moisture, ash and wax contents determined according to standards are shown in Table 1. The results revealed that this fiber has more cellulose contents when compared to other natural fibers like ferula, althaea, pissava, bamboo, arundo donax and coir etc. which shows that Phoenix Sp has more strength, stiffness and structural stability.

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Fig. 3. Diameter of Phoenix Sp fiber (a) Diameter measurement; (b) Distribution of fiber diameter

Table 1. Properties of Phoenix Sp fiber.

Property Values

Diameter (mm) 0.5766 Density (g/cc) 1.2576 Cellulose (%) 76.13

Lignin (%) 4.29

Moisture (%) 10.41

Wax (%) 0.32

Ash (%) 19.69

The tensile test was carried out for 25 samples of Phoenix Sp fibers in each gauge length and their average

tensile strengths were noted. The results revealed that the short fibers have higher tensile strength and vice-versa. This is due to that the short fibers have less number of flaws on its surface, so it has maximum load carrying capacity. The increase in gauge length results in increased number of flaws, which reduced the load carrying capacity of the fiber; hence there is a drop in tensile strength.

3.2. Modal analysis

In free vibration testing the time domain signal is taken for composite beams with different fiber length to identify its fundamental natural frequency is shown in the Fig. 5. The results revealed that the beams with 50 mm fiber length has maximum natural frequency of 25 Hz with an amplitude range of 2.9066 g, whereas the specimen having 30 mm and 10 mm have a natural frequency of 32 Hz and 25 Hz with amplitude range of 1.3789 g and 0.3050 g respectively. The natural frequency for pure resin composite beam is very minimum when compared to resin reinforced with Phoenix Sp fibers. The matrix reinforced with long fibers has maximum amplitude with minimum natural frequencies.

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Fig.4. Frequency domain signal.

4. Conclusion

The newly identified phoenix sp fiber was manually extracted from Phoenix Sp plants and its physical, chemical and mechanical properties were determined. This fiber has more cellulose content, which increases the properties like tensile strength, Young’s modulus and stiffness. Other properties are comparable with available natural fibers like sisal, hemp and coir etc. The maximum tensile strength of Phoenix Sp fiber was determined as 348.95MPa for 20mm gauge length. Because of the above properties the Phoenix Sp fiber has a potential to use as reinforcement in polymer matrix composites. Moreover free vibration analysis was carried out for composite beams under Clamped-Free boundary condition. The composite beam with 10 mm and 50 mm fiber length has a frequency range of 25Hz, but amplitude is more for composite beam with 50 mm fiber length. The composite beam having 30 mm fiber length has a maximum natural frequency of 32 Hz, hence optimum value of fiber length of 30 mm is selected to avoid the condition of resonance.

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