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Experimental Test Effect Of Fiber Glass And Direction Of Strength Matrix Composite Materials Airfoil Profile Fan BladesFull paperJurnalTeknologi

Sugeng Ariyono, Carli, Ariawan Wahyu Pratomo, Hery Tristijanto

Department of Mechanical Engineering Politeknik Negeri Semarang*Corresponding author: s.ariyono@gmail.com

Article history

Received XXXXReceived in revised form XXXXAccepted XXXX

Graphical abstract

Abstract

The use of composite materials is nowadays increasingly widespread. Those materials are not only applied as a cover material (skin) but also as main structure in the mechanical construction. Composite materials commonly used are glass fiber composites (fiber glass composite). The aim of this research is to develop fan blade made of fiber glass composite. This study discusses experimental testing for investigating influence of fiber orientation and matrix material that applied as a fan blade to its mechanical strength. In present study as composite matrix are epoxy and polyester. The composite was manufactured using Hand Lay-Up method and stacked with 6 layers with fiber direction of 0/90 and 45 . The Hand Lay-Up method was chosen because that method is simple and cheap enough. In addition, the specimens then tested using bending test machine based on test standard ASTM D 6272, with the Four-Point Bending method, while for tensile testing using a tensile testing machine (selvopulser) with the standard test ASTM D 3039. The results showed that the tensile and bending strength of composite fiber glass/ epoxy composite is higher than the glass fiber / polyester. Test results also showed that the tensile and bending glass fiber composite with fiber orientation 0/90 has higher tensile than the fiber orientation 45 , meanwhile deflection of the composite with fiber orientation 45 gave higher values (more elastic).

Keywords: Composites, Hand Lay-Up method, glass fiber / epoxy, glass fiber / polyester

2012 Penerbit UTM Press. All rights reserved.

Author et al. / Jurnal Teknologi (Sciences & Engineering) 58 (2012) 8588

20 (2012) 85-88 | www.jurnalteknologi.utm.my | eISSN 21803722 | ISSN 01279696

PAGE 2

1.0 INTRODUCTION

Wind as a source of energy is the most abundant source of renewable energy. Wind energy will remain there as long as the earth is getting energy from the sun. One of the tools that utilize wind mechanical movement is the propeller. Propeller is a component of the machine which is used to transmit power by converting rotational motion into thrust [1][2]. The development of current propeller is very rapid and diverse. Propeller is widely used in the aerospace industry, maritime, and energy machinery, such as the manufacture of aircraft, ships, hovercraft, and various types of turbines [3][4]. Wind turbine has great potential to generate electricity even though from the data, generally, the wind energy potential in Indonesia was not great, but based on a survey and measurement of wind data that has been conducted since 1979, many prospective areas for wind speed annual average of 3.4 - 4.5 m / sec or having energies between 200 kWh / m to 1000 kWh / m. This potential can already be used for small-scale electricity generation to 10 kW[5].

The most important things in the design of wind turbine blades are both form and material. Micro win turbine under 5 kW, the blade is usually made from wood as seen in Figure1. This type of propeller can receive win speed up to 50 m/sec. For larger win turbine the blade mostly made of composite either carbon fiber or glass fiber. Meanwhile most propellers used for aerospace or hovercrafts are made from fiberglass because it needs larger trust [6]. In practice, to obtain high efficiency, fan blades must have certain characteristics, such as a light, stiff, strong, and not easily affected by the environment (such as corrosion), therefore the material used for the manufacture of the fan blades must be appropriately chosen[7].

Composite material is composed of more than one type of material and designed to get a combination of the best characteristics of each of its constituent components. Basically, the composite can be defined as a macroscopic mixture of fiber and matrix. Fiber is a material that is generally much stronger than the matrix and serves to provide tensile strength, while the matrix serves to protect the fiber from environmental effects and damage caused by collision. Composite has great strength and can be designed based on the need of it strength. The direction, composition and type of fiber glass will effect to it strength.

Figure 1.2 kW Wind Turbine with wooden blade

The main benefit of the use of composites is to obtain a combination of properties of high strength and stiffness and light weight type. Composite can also be formed in very unique and complex shape. By choosing an appropriate combination of fiber and matrix materials, the strength of component can be designed properly based on the need of it application. This research shows simple example of the effect of direction of fiber on its strength by using tensile test, bending test and finally dynamic test on real condition with CPP machine.

2.0 FABRICATION METHOD

Hand lay-up method was used to manufacture the blade. First step was to design the shape of blade and using CAM the blade was manufactured using wood as raw material. Whereas to find the appropriate direction and composition of fiber, the specimen was made in 4 different compositions [8]. The specimen was then tested using tensile test and bending test. Blade pattern made from wood was used to manufacture mold made of fiber glass. A release agent, usually in either wax or liquid form, is applied to remove the finished mold easily from the pattern blade as seen in Figure 2 [9]. The surface of the mold should be polished and lay up with release agent before it is used to make blade. Lay-up technique with fiber orientation epoxy 0/90o, the blade was fabricated.

Figure 2. Blade pattern and mold master to fabricate next blade

3.0 EXPERIMENTAL METHOD AND DISCUSSION3.1 Tensile TestTensile and bending test specimens ,as seen in Figure 3, were made in the form of composite plates were manufactured by hand lay-up method, created in the six layers of glass fiber Woven Roving type (WR). Geometry and dimensions of the tensile and bending test specimens adapted to standard ASTM D 3039 and ASTM D 6272 (four point bending)[10].

Figure 3. size of specimen based on ASTM D3039

Test specimens of composite bending shape refers to the standard ASTM D 6272 (four point bending), which has dimensions of length = 100 mm and width = 10 mm. Specimen thickness = 3 mm as seen in figure 4.

Figure 4 specimens of blade material

Tensile test results data using Servopulser engine, with load (P) by 2 tons (2000 kg) can be seen in the table 1. The table shows that the results of tensile testing of glass fiber composites with epoxy resin matrix with fiber orientation 0 / 90 obtained results tensile test maximum voltage average of 112.8 MPa. As for the Epoxy 45, the average maximum stress of 82.34 MPa. Results of tensile test for fiber glass with polyester resin matrix with fiber orientation 0 / 90 tensile test results obtained maximum voltage average of 118.86 MPa. As for the polyester 45, the average maximum stress of 90.49 MPa. From the above average results can be seen in Figure 5.

Table 1. Results of Tensile test.NoSpecimensThickness(mm)Wide(mm)Length ( Lo )(mm)Tensile mak.( Mpa )

1Polyester 453,5020,0100,883

2Polyester 453,6521,998,892

3Polyester 453,2021,6597,7595

4Polyester 0/903,1019,5093,7112

5Polyester 0/902,8021,4594,45136

6Polyester 0/903,3019,6589,05107

7Epoxy 454,1021,70101,7861

8Epoxy 452,6022,5091,10105

9Epoxy 453,3521,3098,480

10Epoxy 0/903,0020,2096,7595

11Epoxy 0/903,0519,5096,25124

12Epoxy 0/903,1019,096,50118

Figure 5. Diagram of the influence of the orientation of the fibers and the matrix of the maximum tensile stress

The average tensile strength from table 1 can be plot into graph such as in Figure 5. Maximum tensile strength occurs in the second bar with value 118.86 Mpa. This indicates that the Polyester with 90o fiber direction has better strength compare to Epoxy 0/90o. Figure 1 indicates that the direction of orientation of the fibers in the sample influence on mechanical properties, especially tensile strength composite. Tensile strength was greatest in the direction of fiber composites with 0 / 90. This can be explained by looking at the analysis of microscopic stress acting on the composite. Direction of orientation is important in strengthening the composite. Since the direction of fiber orientation is closely related to the deployment of the forces acting on the composite. Distribution of the maximum fiber occurs when the fiber direction parallel to the direction of loading. Strength of the composite will be reduced by changing the angle of the fiber, so that the composite will have a high strength if the fiber structure and the force exerted are unidirectional. However, its strength will be weakened if the structure of both the opposite direction or perpendicular. Matrix composites have not actually chemically bond with the filler fibers but only happens bonding interface (bond in physics). Therefore, in this study showed that for unidirectional fibers (0 / 90) have the largest tensile strength; this is because the fiber is unidirectional and perpendicular to the force exerted on the composite. Fibers are transverse to the direction of loading does not provide reinforcement, will actually weaken. It is also due to the unidirectional fibers and fibers that transverse or perpendicular interfacial bonding does not occur (the fibers) are against the force of the composite. The greater force is starting to take some fiber (debonding) because of the pull force on the tip.

Figure 6 , Left, a fracture with fiber orientation 0 / 90, and Right, fracture with the fiber orientation 45.

Because of the connective force between the matrix with these fibers, may also explain why the composite fibers have a tensile strength 45 smaller than the fiber composite 0 / 90, this is because the power of connective fiber between the matriknya weak even weaker than the bonding of atoms in matrix itself. Consequently when it gets there loading shear force on its matrix which then separated from the matrix fiber bond.

3.2 Bending TestTesting was conducted using a four point bending method, the method of measurement have been more accurate results than the Three-point bending method. The result of bending test can be seen in Table 2. Table 2. Comparison bending test between Polyester and EpoxyNoSpesimenBending(Mpa)SpesimenBending(Mpa)

1Polyester 4570.6589Epoxy 4584.7081

2Polyester 4579.9360Epoxy 4580.1861

3Polyester 4583.0580Epoxy 4583.8537

4Polyester 0/9075.9126Epoxy 0/90117.4991

5Polyester 0/9084.7086Epoxy 0/90114.4567

6Polyester 0/9079.1527Epoxy 0/90125.7210

The table shows the bending test results for the fiber glass with polyester resin matrix and fiber orientation 0 / 90 has an average stress of 79.92 MPa. Meanwhile the polyester with fiber orientation of 45 has the average stress of 77.88 MPa. Bending test results for glass fiber with epoxy resin matrix and fiber orientation 0 / 90 has an average stress of 119.22 MPa. The epoxy resin and fiber orientation of 45, has the average stress of 82.91 MPa. Figure 7 shows the average bending test for every specimen.

In the bending test, at the top of the specimen subjected to pressure, and the bottom had traction. Failure caused by the bending test composites fractured at the bottom of not being able to withstand tensile stress.

Propeller used in this experiment made of glass fiber with epoxy resin matrix and fiber orientation 0 / 90. This composition has bending test higher than other, even though the tensile strength is lower than the fiber glass with polyester resin matrix and fiber orientation 0 / 90. Higher bending stress give better properties to withstand dynamic load [11][12]. Propeller especially used as hovercraft propeller have dynamic load higher than used for wind turbine.

Figure 7 Diagram of the influence of the orientation of the fibers and the matrix of the maximum bending stress

Blade fabricated from Multi-Wing was used as bench mark to design new profile blade used in this experiment. Material used by Multi-Wing was also tested for comparison in this experiment. Figure 8 shows the result of the tensile strength.

Figure 8 Diagram of the maximum tensile stress for each test specimen and the maximum tensile stress to the fan blade from Muti-Wing

Figure 8 shows that the maximum tensile strength of the specimens was higher (except Epoxy 45) when compared with products from Multi-Wing. Multi-Wing products with the axial fan and other various types that are used for a hovercraft are made from thermoplastic (glass reinforced polypropylene). The thermoplastic material has a good flexural modulus when compared with materials used in this experiment.

3.3 Results and Analysis of Static and Dynamic Testing Fan Blade using Control Pitch Propeller (CPP)

Control Pitch Propeller (CPP) as seen in figure 9 is used to test the capacity of the fan blade on constant rotation with varying pitch angle and dynamic moves. CPP control mechanism serves to adjust the angle of pitch propeller (blade angle) with the aim of producing a variation of thrust (thrust). This mechanism typically used in aircraft, ships, hovercraft, etc.. The working principle of CPP control mechanism is by setting or changing the pitch angle of the propeller. Hydraulic is used to push linkage mechanism to change pitch angle position.

Fan blade strength testing was done in two ways: static testing and dynamic testing. Static testing was conducted to determine the maximum thrust occurs in every corner of his pitch. While the dynamic testing was conducted to determine the ability of the fan blade withstand varied styles arising from the rotation and movement of the fan blade pitch angle changing automatically from 0 to 55, the number of revolutions reaches 1,000,000 rounds or until the fan blade broke / broken

Figure 9 Control Pitch Propeller (CPP) machine

The purpose of static test is to find out the optimum pitch angle to produce maximum thrust. Static test was carried out when the blade was rotated at 1500 rpm for 30 minutes. Thrust was recorded using load cell. Zero degrees was set when there was no thrust at all or load cell indicated the minimum value. Static test thrust force was done by adjusting the pitch angle from 0 to 55 with increment of 5o for every cycle. Figure 10 shows the result of thrust resulted from static test. The graph shows that the maximum thrust occur when the pitch angle was set at 35o.. Figure 10. Thrust force for every pitch angle, blade rotation 1500 rpm.

The purpose of dynamic test is to investigate the effect of varied resulted thrust to the performance of blade. Dynamic testing was carried out when the blade was rotated at constant speed of 3000 rpm. The blade angle then rotated on its axial blade axis to find out the zero reference where there was no trust. Experiment was carried out by adjusting the pitch angle from 0o to 55o with increment of 5 degrees. The blade was twisted from 0o to 5o while it rotated at 3000 rpm for 15 minutes. Thrust resulted was measured using load cell. Physical check should be done to investigate damage due to dynamic test after one cycle test completed. One cycle test mean every 15 minutes running in dynamic test for increment pitch angle of 5 degrees, hydraulic push and pull adjusted rod to twist blade from 0o to pitch angle required automatically. Every cycle was repeated 3 times to get good data. Second data was taken when the blade was twisted from 0o to 10o and running in the same speed 3000 rpm for 15 minutes. Test was repeated until the pitch angle reach 55o.

Experiments conducted over 1 million rounds or until there is damage to the fan blade. Practically over one million rounds the blade condition shows no damage and blade remains in good condition.

4.0 CONCLUSIONFrom the tensile test results, has a polyester resin matrix tensile stress which does not differ much from the epoxy resin matrix, the matrix is due to function only as an adhesive material (bonding). For best results composites have tensile strength and flexural strength of the best is the direction of fiber composites with 0 / 90. The blade can withstand and reliable after over one million rounds on dynamic test. No fiber pullout after completed the test. Further investigation is needed to test in the real condition due to environment condition.

Acknowledgement

We would like to appreciate gratefulness to the ministry of high education for giving research grand. We also would like to appreciate gratefulness to Politeknik Negeri Semarang especially department of mechanical engineering who give us opportunity to use the laboratory to conduct the experiment.

References

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