STUDY OF MECHANICAL PROPERTIES OF GLASS FIBRE REINFORCED EPOXY COMPOSITE

ISSN: 2395-0560 International Research Journal of Innovative Engineering

www.irjie.com Volume1, Issue 4 of April 2015

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STUDY OF MECHANICAL PROPERTIES OF GLASS FIBRE REINFORCED EPOXY COMPOSITE

Smita G. Mekalke Mechanical Engineering Department, Jain College of Engineering, Belagavi, 590014, India.

Abstract In the dissertation work an attempt is made to study the Mechanical properties of Glass Fibre Reinforced Epoxy Composite and Wear Resistance of the material using Design of Experiments (DOE) approach. The composite is fabricated using Epoxy Resin and woven Glass Fibre mats of different Grams/Square Meter (GSM) values. Hand lay-up technique is used for fabrication of the composite. The composite is tested as per ASTM standards for various mechanical properties such as Tensile Strength, Impact Strength and Bending Strength. The composite is also tested for Wear Re-sistance by varying the process parameters during the test such as load applied, loading time and glass fibre GSM. As per the Design of Experiments approach, the three parameters are varied in two levels and single replicates i.e. L8 array. The specified number of experiments is conducted to obtain the optimum condition for Wear Resistance by the composite.

Keywords GFRP, Tensile strength, Impact Strength, Bending Strength, Wear Resistance, DOE

1. Introduction The unique and diverse characteristics of composite materials have increased in their utilisation worldwide. From feather-weight fly fishing rods to high performance airplane parts, the use of fiber reinforced composite materials is becoming more popular due to their high strength to weight ratio combined with easy manufacturing methods. Fiber reinforced poly-mer matrix consists of reinforcing fibers and polymer resin. The fibers are considered as principal load carrying constituent of the composite, while the role of polymer matrix is to transfer the load between fibers as well as provide corrosion re-sistance damage tolerance and thermal environmental stability.

Fillers are used along with various commodity as well as engineering polymers to improve the properties and reduce the cost. Incorporating inorganic mineral fillers into plastic resin improves various physical properties of the materials such as mechanical strength, modulus etc. In general the mechanical properties of particulate filled polymer composites depend strongly on size, shape and distribution of filler particles in the polymer matrix and extend of interfacial adhesion between filler and matrix. At present, epoxy resins are widely used in various engineering and structural applications such as electrical industries, and commercial and military aircrafts industries. In order to improve their processing and product performances, and to reduce cost, various fillers are introduced into the resins during processing. However polymeric composites are susceptible to me-chanical damage, when subjected to tension, wear and flexural loads resulting in interlayer delamination. Over the past several decades enormous efforts have been made to study the mechanical characteristics of composites.

1.1 Overview

The dissertation work deals with determining the mechanical properties and wear resistance of glass fibre reinforced epoxy composite. The composite is manufactured by hand-layup process. Specimens were cut and tested according to ASTM standards. The mechanical properties like Tensile Strength, Bending Strength and Impact Strength of the material were studied. Wear resistance of the composite was checked using the Design of Experiment (DOE) approach by varying the Load, Speed and Loading time on the specimen.




1.2 Aim

i) Investigation of the mechanical properties such as Tensile Strength, Bend Strength and Impact Strength of the GFRP. ii) Investigation of the Wear resistance of the composite. iii) Using Design of Experiments approach to analyze the Wear resistance of the composite.

2. Testing of Mechanical Properties The experimental procedure carried out during the course of the dissertation work mainly deals with two aspects i.e. Fabri-cation of the composite specimen and Testing of the fabricated specimen for various mechanical properties. The composite was fabricated using the conventional Hand layup method using the following materials:

o Epoxy Resin (Araldite LY556) o E-glass Fiber (Woven mat) o Hardener (HY951)

The fiber and the matrix were taken in the ratio of 40:60. The quantity was decided based on the calculations of fibre vol-ume fraction. Following tests were conducted in the present work to study the various mechanical properties of the fabricated composite: 1) Tensile Test (ASTM D3039) 2) Three Point Bending Test (ASTM D790) 3) Impact Test (Charpy) (ASTM D256) 4) Wear Test (ASTM G65)

2.1. Tensile Test

Tensile tests were carried out on Universal Testing Machine (Instron) to know the tensile strength of the composite material. The composite specimens were cut in proper sizes (250*25mm) as per ASTM standards i.e. ASTM D 3039 for tensile test. These tests were carried out on the specimens at room temperature. Specimens were placed in the flat hatched grips and were pulled until failure. The test specimen after failure is shown below. An extensometer/strain gauge was used to determine the elongation and tensile modulus.

Figure 1. Tensile test specimen after failure

2.2. 3-Point Bend Test Bending strength is also known as modulus of rupture or fracture strength, which is mechanical parameter of materials. It is defined as a material's ability to resist deformation under bending loads. The transverse bending test is most frequently em-ployed, in which a rod specimen having either a circular or rectangular cross-section is bent until fracture occurs using a three point bend test technique. The bending strength represents the highest stress bearing capacity of the material at its moment of rupture. 3-Point Bend Testing was carried on rectangular specimens (127 x 12.7 mm) of composite using Universal Testing Machine (TUE-C 400) of 100 KN capacities with 1% accuracy at ambient temperature according to the procedure described in ASTM D 790. The test was initiated by applying the load on the specimen at the specified rate. The deflection was measured by a gauge under the specimen in contact with it in the center of the support span.




2.3. Impact Test

The impact behavior of the composite is experimentally investigated using the notched Charpy Impact test specimen. For this purpose, Impact Testing Machine (AIT- 300 N) was used which has a maximum energy of pendulum of 300 J. The specimens were carefully cut to the required dimensions of the impact test according to ASTM D256. The notched Charpy impact specimen dimensions were (55*12.5 mm) having U notch of 450 with a depth of 0.5 mm prepared by milling machine. The notch allows for a predetermined crack initiation location. The Charpy impact test method works by placing a notched specimen (with the notch facing away from the point of contact) into a large machine with a pendulum of a known weight. The pendulum is raised to a known height and allowed to fall. As the pendulum swings, it impacts and breaks the specimen, rising to a measured height. A digital attachment for recording the energy absorption was used to perform the tests. The difference in the initial and final heights is directly proportional to the amount of energy lost due to fracturing the specimen.

2.4. Wear Test

Abrasion testing is used to test the abrasive resistance of solid materials. Materials such as composites can be tested with this method. The intent of this test method is to produce data that will rank materials in their resistance to sliding abrasion under a specified set of conditions and can help to predict the life time of a material. Abrasive wear tests were conducted on the composite specimen according to ASTM standards i.e. ASTM G 65. The wear tests were conducted on a pin-on-drum abrasive wear tester, designed for standard wear tests described in ASTM standards. In this method, the test specimen translates over the surface of an abrasive paper, which is mounted on a revolving drum, with the resulting wear of the material expressed as volume loss. An alumina (Al2O3) abrasive which is substantially harder than either the matrix or the rein-forcement was used. The specimen is continuously in contact with new abrasive surface. A static normal load, L, was applied directly on the specimen to press it against the center of the drum that caused wear. Design of Experiments approach (DOE) was used to conduct this test. By Taguchi method, L8 array was used containing 3 parameters and 2 levels. Load, Loading time and Speed are the three parameters that were varied. All tests were carried out in dry ambient air laboratory conditions.

3. Results & Discussion 3.1. Tensile Test

The results obtained in the form of Load applied and change in Displacement is used to calculate the values of Stress and Strain. A graph of Stress v/s Strain is plotted and the slope of the line of plot gives the Youngs Modulus. The results obtained in the form of Ultimate Tensile Strength (UTS) & Youngs Modulus (E) by 3 trials for the GFRP specimen of both the GSM values are as follows:

Composite Specimen Ultimate Tensile Strength (MPa) Youngs Modulus (GPa) 415 GSM Maximum UTS = 73.33

Average UTS = 71.11 Maximum E = 1.92 Average E = 1.86

600 GSM Maximum UTS = 113.636 Average UTS = 104.54

Maximum E = 2.27 Average E = 2.183

3.2. Bending Test

The readings obtained after the 3-point bending test on the GFRP specimen in the form of load applied & CHT is used to calculate the Flexural strength, Flexural Modulus & Inter Laminar Shear Strength (ILSS). The results hence are as shown below:

Composite Specimen Average Flexural Strength (N/mm2 )

Average Flexural Modulus (GPa)

Average ILSS (N/mm)

415 GSM 275.5 8.369 413.39 600 GSM 265 8.668 581.60




3.3. Impact Test

The result obtained at the end of the impact test in the form of Impact Energy is used to find the Impact Strength. The Impact Strength was plotted on a graph to conclude on the Final Average Impact Strength of both the GFRP specimens using three trials each. The results obtained are as follows:

Composite Specimen Impact Energy (J) Impact Strength (kJ/m2) 415 GSM 4.67 124.48 600 GSM 12.67 230.30

Table 3. Impact Test Results

3.4. Wear Test

The Design of Experiments (DOE) approach is used to conduct the wear test. L8 array under Taguchi method is used which varies two levels and three parameters i.e. Load, Loading Time and Speed. The results obtained after conducting the wear test as per Design of Experiments approach was used to calculate the Wear Velocity, Wear Volume & Wear coefficient. The results of the tests conducted are shown below:

o Glass/Epoxy specimen of 415 GSM: Initial Weight

(gms) Speed (rpm)

Load (kgs)

Time (min.)

Final Weight (gms)

Weight (mg)

Wear Coefficient (m2/N)

2.9761 300 1.5 2 2.9742 1.9 6.55 * 10-14 2.6096 300 1.5 4 2.6054 4.2 7.25 * 10-14 2.9739 300 3 2 2.9694 4.5 7.76 * 10-14 3.0520 300 3 4 3.0465 5.5 4.74 * 10-14 2.7963 600 1.5 2 2.7933 3.0 5.16 * 10-14 3.0232 600 1.5 4 3.0192 4.0 3.44 * 10-14 2.5965 600 3 2 2.5924 4.1 3.53 * 10-14 2.5009 600 3 4 2.4952 5.7 2.45 * 10-14

Table 4. Wear Test Readings for 415 GSM

o Glass/Epoxy specimen of 600 GSM:

Initial Weight (gms)

Speed (rpm)

Load (kgs)

Time (min.)

Final Weight (gms)

Weight (mg)

Wear Coefficient (m2/N)

5.2134 300 1.5 2 5.2099 3.5 1.21 * 10-13 4.5458 300 1.5 4 4.5399 5.9 2.04 * 10-13 4.5547 300 3 2 4.5510 3.7 6.38 * 10-14 4.7545 300 3 4 4.7477 6.8 5.86 * 10-14 5.2576 600 1.5 2 5.2537 3.9 6.71 * 10-14 4.3962 600 1.5 4 4.3910 5.0 4.30 * 10-14 4.4765 600 3 2 4.4723 4.2 3.61 * 10-14 5.0737 600 3 4 5.0683 5.4 2.32 * 10-14

Table 5. Wear Test Readings for 600 GSM

The results were then analysed using the Minitab software. Anova & Response Table for Means & Signal to Noise Ratios for both the GFRP specimens was obtained as shown below.




Figure 2. Main Effects Plot for Means for 415 GSM

Figure 3. Main Effects Plot for SN ratios for 415 GSM

Figure 4. Main Effects Plot for Means for 600 GSM




Figure 5. Main Effects Plot for SN ratios for 600 GSM

4. Conclusion From the Tensile tests conducted on the GFRP composite specimens it can be concluded that as the GSM value of the glass fibre in the composite increases, the tensile strength too increases for the given percentage (40: 60) of glass fibre and resin. The 3-Point Bend Test conducted on the GFRP gave the responses in terms of Bend load and change in height (CHT) through which the Flexural strength was calculated. The higher flexural strength for 415 GSM than 600 GSM can be due to inclusions and voids in the microstructure of the composite specimen. Impact test conducted on the GFRP specimens yielded results in terms of impact load that the specimens could bear before fracture. The impact energy of the composite increases with an increase in the GSM value of the glass fibre reinforcement. The results obtained from Wear tests were used to analyse and interpret the results using Design of Experiments (DOE) approach and Minitab software. The results show the Mean values, Signal to Noise (SN) ratio values and the rank of the different parameters that varied. It is observed that as the GSM values of the GFRP specimens and the load increase, the wear observed on the specimen increases i.e. the wear resistance of the specimen decreases.

ACKNOWLEDGEMENT I am greatly indebted to Prof. Nikhil R. & Prof. G. S. Guggari (I.P.E., G.I.T., Belagavi), for their guidance & unending support throughout the course of the work. I deeply thank Dr. Shivkumar S., Professor (I.P.E., G.I.T., Belagavi), for his guidance and also for being a great source of knowledge. I would like to express my sincere gratitude to Mr. Suhas P. Chandak (Director), Mr. Uttam S. Gurjar (Production Manager) and supporting staff, Vega Industries Pvt, Ltd., Belagavi, for providing me with an opportunity to carry out the dissertation work in their esteemed organization and for training/guiding me. I would also like to express my deep gratitude to Prof. D. B. Patil, H.O.D. & all the staff members, Mechanical Engineering Department, J.C.E., Belagavi, for being a constant source of encouragement.




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STUDY OF MECHANICAL PROPERTIES OF GLASS FIBRE REINFORCED EPOXY COMPOSITE

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