DETERMINATION OF MECHANICAL PROPERTIES NATURAL RUBBER COMPOUNDS USING DOUBLE SHEAR TEST PIECES

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1 International Journal of Civil Engineering and Technology (IJCIET) Volume 9, Issue 8, August 2018, pp , Article ID: IJCIET_09_08_005 Available online at ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed DETERMINATION OF MECHANICAL PROPERTIES NATURAL RUBBER COMPOUNDS USING DOUBLE SHEAR TEST PIECES R. Ismail Institute for Infrastructure Engineering and Sustainable Management (IIESM), Universiti Teknologi MARA, Shah Alam, Selangor, Malaysia A. Ibrahim Faculty of Civil Engineering, Universiti Teknologi MARA, Shah Alam, Selangor, Malaysia M. Rusop NANO-SciTech Centre, Institute of Science, Universiti Teknologi MARA, Shah Alam, Selangor, Malaysia A. Adnan Faculty of Civil Engineering, Universiti Teknologi Malaysia, Skudai, Johor, Malaysia ABSTRACT This paper presents the results of an investigation into the potential application of Natural rubber (NR) containing Carbon Nanotubes (CNTs) and Carbonyl Iron Powder (CIP) by measuring its shear modulus and damping ratio. Rubber bearings containing natural rubber have been used for isolation of structure from external vibration like earthquake. The properties of damping ration and shear modulus were determined using double shear test pieces. Four types of rubber compounds were mixed accordingly with different CNTs and CIP loadings. It is observed that the shear modulus and damping ratio of CNTs filled rubber composites are remarkably higher than that of raw rubber indicating the inherent reinforcing potential of CNTs. Key words: Mechanical properties, natural rubber, double shear test. Cite this Article: R. Ismail, A. Ibrahim, M. Rusop and A. Adnan, Determination of Mechanical Properties Natural Rubber Compounds Using Double Shear Test Pieces. International Journal of Civil Engineering and Technology, 9(8), 2018, pp

2 R. Ismail, A. Ibrahim, M. Rusop and A. Adnan 1. INTRODUCTION The effect of earthquakes has been one of the major concerns of scientists and engineers for a long time. Many studies were conducted on mitigating seismic responses of structures due to earthquake events [1-6]. Two basic parameters for the design of elastomeric bearings are the shear stiffness and the damping capacity (damping coefficient), since it indicates how much vibration energy is attenuated during a cycle of vibration. Rubber bearings have been used for isolation of structure from external vibration like earthquake [7-8] and also been practised in machinery and equipment s [9]. Traditional rubber-made base isolators form the critical component in the base isolation systems for civil structures. In recently days, they have been challenged by vulnerability during unexpected earthquake [10]. There have been efforts from researchers in investigating the modulus and damping in base isolation system [11-12]. However, most researches on polymer nanocomposites focus on stiff polymer matrix such as epoxy and thermoplastics, while only a few are dealing with CNT-reinforced elastomers [13-20]. 2. MIXING PROCESS OF RUBBER COMPOUNDS The compounding formulations (in parts per hundred parts of rubber (phr)) used in this work are listed in Table 1. The compounding of natural rubber with CNTs and other additives is carried out in a two-roll mixer (at 140 C), following the conventional technique. The specimens were fabricated with different CNTs and CIP loadings as shown in Table 2. Table 1 Materials for Compounding Ingredients (pphr) Natural Rubber (SMR 10) Carbon Nanotubes (%) Carbon Black (SAF) N110 (%) Antioxidant Zinc Oxide (ZnO) Stearic acid (St.Acid) TMQ Sulphur CBS TMTD Table 2 CNTs and CIP loadings Speciments Descriptions %CNTs %CIP A0 Natural Rubber-Conventional 0 0 A1 Natural Rubber with CNT filler) 1 0 A2 Natural Rubber with CIP filler) 0 20 A3 Natural Rubber with CIP and CNT filler) CURING PROCESS OF RUBBER COMPOUND Four differnet rubber compounds were used to vulcanize double shear test pieces. The compounds were vulcanized using specific of double shear test piece which has two cavities. Two samples of double shear test piecs for each rubber compound were prepared. Figure 1 shows the mould of double shear test pieces with three cavities. Double shear test piece cured at the temperature of 140 C for 60 minutes. Figure 2 shows the double shear test piece according to number of compounds editor@iaeme.com

3 Determination of Mechanical Properties Natural Rubber Compounds Using Double Shear Test Pieces Figure 1 The mould of double shear test piece Figure 2 Samples of double shear test pieces 4. TEST PROCEDURE The double shear test piece is only used for characterizing rubber material in the material development particularly in determining mechanical properties of rubber. In the current testing work, double shear test peace test is used to determine the damping and shear modulus properties of rubber. Figure 3 shows the dimension of double shear test piece as a reference. The overall dimension of test piece is not controlled and every test piece shows different dimensions. The most important dimensions are rubber thicknesses and rubber to metal bonding areas. Each test pieces was used and placed on the testing jig. All screws on the test jig were tightened properly before the test is commenced. Figure 4 shows the overall test setup of dynamic test on the testing machine platform. Dynamic test were undertaken on a MTS Multi axis servo-hydraulic testing machine. The load-cell capacity of the testing machine is 25kN with a stroke displacement ±75mm. All specimen were dynamically tested by varying the strain amplitude of 5% and 10% from the rubber thickness with frequency of 0.5, 2.5, 5.0, 0.7 and 10 Hz. These testing conditions were applied referring to the BS EN15129:2009 document : Effect of Strain Amplitude. Five consecutive cyclic for each strain amplitude was programmed to record the data of force and displacement. The tests were performed in ascending order of strain amplitude 39 editor@iaeme.com

4 R. Ismail, A. Ibrahim, M. Rusop and A. Adnan Figure 3 Double shear test pieces Figure 4 Overall test setup 5. TESTING RESULT All the data of force and displacement were used to calculate shear modulus, G* and damping ratio according to the BS EN15129:2009. The results for all rubber specimens are shown in Figure 5-8. The difference of shear modulus for each rubber compound is very significant when the strain amplitude is varied. The shear modulus for all compounds is higher at 5% strain amplitude and decreased slightly at 10% strain amplitudes. It is found that strain dependence with the shear modulus. The compound with CIP showed inconsistent at damping ratio at 5% strain amplitude. However, the trend of damping ration at 10% strain amplitude is increasing which is in the range between 2.8 and 5.2 damping ration editor@iaeme.com

5 Determination of Mechanical Properties Natural Rubber Compounds Using Double Shear Test Pieces Figure 5 Result of shear modulus for 5% stain. Figure 6 Result of shear modulus for 10% stain Figure 7 Result of damping ratio for 5% stain 41 editor@iaeme.com

6 R. Ismail, A. Ibrahim, M. Rusop and A. Adnan Figure 8 Result of damping ratio for 10% stain 6. CONCLUSIONS This paper presents the design, testing and modelling of a base isolator with variable stiffness and damping to be used for base isolation system of civil structures. It is believed that the small size and high aspect ratio of CNTs leads to dramatic increase in surface area, hence enhancement in shear modulus and damping. Based on the results of the study, it can be concluded that: Double shear test piece can be used to determine the shear modulus and damping properties of rubber compound. This method is an indicator to evaluate the properties of rubber compounds. The variation odf frequency exhibited difference shear modulus and damping ratio. The higher strain amplitude, the shear modulus will decrese. The damping ration is inconsistent at low strain amplitude. Nevertheless, the damping ration increased when the strain amplitude is increased. The rubber compound od A21/A22 indicated the high damping ration among the other rubber compounds by varying the frequency at 10% astrain amplitudes. ACKNOWLEDGEMENTS The authors would like to acknowledge that this research has been carried out as part of a project Bestari Perdana Research Grant with File No 600-IRMI/PERDANA 5/3 BESTARI (081/2018) internal fund, funded by Universiti Teknologi MARA (UiTM), Institute of Quality and Knowledge Advancement (InQKA) and support from Faculty of Civil Engineering, Universiti Teknologi MARA (UiTM). REFERENCES [1] R. Ismail, A. Ibrahim, H. Hamid, M. Rusop, A. Adnan (2018). Experimental study on mechanical properties of elastomer containing carbon nanotubes. Journal of Engineering Science and Technology, 13(3), [2] Ismail, R.; and Ismail, M.I. (2017). Dynamic analysis of concrete faced rockfill dam using finite element method. Journal of Engineering and Applied Sciences, 12(7), [3] Ismail, R.; and Abdul Karim, M.R. (2017). Concrete bridge pier performance under earthquake loading. Journal of Engineering and Applied Sciences, 12(9), editor@iaeme.com

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