ABSTRACT
This research presents the development of metal matrix composite using coconut shell ash as the reinforcement for automotive applications. Test samples were produced by stir casting method and machined into standard sizes for the purpose of determining micro structural analysis, physical, thermal, corrosion, mechanical and wear properties. The results obtained were compared with standard composite materials used in the production of connecting rod. The metal matrix composites (MMC‟s) were prepared by addition of 3, 6, 9, 12 and 15wt% CSAp particulates. The results of the microstructural analysis of the composites revealed the uniform distribution of the coconut shell ash particles. The increase in reinforcement volume fraction resulted in the decrease of matrix grain size in the composites. The results obtained also showed that addition of coconut shell ash particles reinforcement to Al-Si-Fe alloy increased the tensile strength and the hardness value of composites, but slightly reduced the impact energy. It is observed that, as the applied load increases, the wear rate also increases. This is because, whenever applied load increases, friction at the contact surface of the material and rotating disc obviously increases. For optimum service performance of this alloy, coconut shell ash particle addition should be between 6-9% by weight of CSAP particulates and not exceed 9% in order to develop better necessary properties. A sample of the produced MMCs connecting rod was tested using a Toyota 12 valve model E series automobile engine to determine performance and effectiveness of the device. The results obtained showed a fuel consumption saving of 0.0034 liters/min and it can be deduced that high improvement in combustion efficiency could be achieved compared to the regular connecting
TABLE OF CONTENTS
Title page – – – – – – – – – i Declaration – – – – – – – – – iv Certification – – – – – – – – – v Acknowledgement – – – – – – – – vi Abstract – – – – – – – – – vii Table of Content – – – – – – – – viii CHAPTER ONE INTRODUCTION
1.1. Background to the Study – – – – – – 2
1.2 Statement of Research Problem – – – – – 3 1.3 The Present Research – – – – – – – 5 1.4 Aim and Objective of the study – – – – – 5 1.4 Significance of the Study – – – – – – 6 1.5 Scope of the Work – – – – – – – 6 CHAPTER TWO LITERATURE REVIEW 2.1 Metal Matrix Composite (MMCS) – – – – – 7 2.2 Mechanical Properties of MMCS – – – – – 7 2.3 Properties of Aluminium Matrix Composites (AMCS) – – 11 2.4 Types of AMCS – – – – – – – 13 2.4.1 Particle Reinforced Aluminium Matrix Composites (PAMCS) – 14 2.4.2 Short Fibre and Whisker-Reinforced Aluminium Matrix Composites (Sfamcs) – – – – – – – – 15 2.4.3 Continuous Fibre-Reinforced Aluminium Matrix Composites (CFAMCS) 16
2.4.4 Monofilament Reinforced Aluminium Matrix Composites (MFAMCS) 16
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2.5 Effect of Ceramic Reinforcements on the Behaviour of Aluminium Matrix in AMCS – – – – – – – 17 2.5.1 Intrinsic Effects of Ceramic Reinforcements – – – – 17 2.5.2 Extrinsic Effects of Ceramic Reinforcement – – – – 18 2.6 Applications of AMCS – – – – – – 18 2.7 Review of Past Works – – – – – – – 19 2.8 Nigeria Coconut – – – – – – – 20 2.9 Connecting Rod – – – – – – – 22 2.9.1. Forces on Connecting Rod (I) – – – – – 25 CHAPTER THREE MATERIALS AND METHODS 3.1 Experimental Procedure – – – – – – 29 3.2 Materials – – – – – – – – 29 3.3 Equipment – – – – – – – – 29 3.4 Method – – – – – – – – 30 3.4.1 The Processing and Chemical Analysis of the Coconut Shell Ash – 30 3.4.2 Specimen Preparation – – – – – – – 32 3.4.3 Density Measurement – – – – – – – 33 3.4.4 X-RAY Diffractometer (XRD) Analysis – – – – 34 3.4.5 Microstructural Analysis – – – – – – 35 3.4.6 Hardness Testing – – – – – – – 35 3.4.7 Tensile Test – – – – – – – – 36 3.4.8 Impact Energy Test – – – – – – – 36 3.4.9 Wear Test – – – – – – – – 36 3.4.10 Thermal Analysis – – – – – – – 37
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3.4.11 Corrosion Test – – – – – – – – 37 3.4.12 Design of the Connecting Rod – – – – – 39 3.4.13 Small End of the Connecting Rod – – – – – 45 3.4.14 Big End of the Connecting rod – – – – – 46 3.4.15 Connecting rod shank – – – – – – – 46 3.4.16 Casting Process – – – – – – – 51 3.4.17 Fabrication (Casting and Machining) of the Connecting Rod – 55 3.4.18 Forces Acting on Connecting Rod (ii) – – – – 59 3.4.19 Inertia Bending Forces – – – – – – – 61 3.5 Finishing Operation (Machining) – – – – – – 69 3.5.1 Heat Treatment (solution – treatment and aging. “STA”) – – 69 3.5.2 Performance Test on the Connecting Rod – – – – 70 CHAPTER FOUR RESULTS AND DISCUSSIONS 4.1 Results – – – – – – – – – 73 4.2 Characterization of the Coconut Shell Ash – – – – 73 4.2.1 Particle Size Analysis of the Coconut Shell Ash – – – 73 4.2.2 Density of the Coconut Shell Ash Particle – – – – 73 4.2.3 Refractoriness of the Coconut Shell Ash Particles – – – 74 4.2.4 XRF Chemical Composition Analysis of the Coconut Shell Ash Particles – – – – – – – – 74 4.2.5 Compositional Analysis and Microstructure of the Coconut Shell Ash Particles (CSAP) – – – – – – 75 4.2.6 FTIR Analysis of the Coconut Shell Ash Particles – – – 76 4.3 Macrostructural Observations – – – – – – 78 4.4 Density of the Composites – – – – – – 79
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4.5 Microstructural and the Interfacial Study of the Composites – – 81 4.5.1 X-Ray Diffraction Analysis (XRD) – – – – – 81 4.5.2 Microstructural Analysis of Composites – – – – 82 4.6 Hardness Values – – – – – – – 88 4.7 Tensile Properties – – – – – – – 89 4.8 Impact Energy – – – – – – – – 93 4.9 Wear Behaviour – – – – – – – 94 4.10 Thermal Behaviour – – – – – – – 100 4.11 Corrosion Behavior – – – – – – – 102 4.12 Test of the connecting rods produced – – – – 104 CHAPTER FIVE 5.0 CONCLUSION AND RECOMMENDATION 5.1 Conclusion – – – – – – – – 111 5.2 Recommendations for Further Studies – – – – 113 References – – – – – – – – 115 Appendices – – – – – – – – 120
CHAPTER ONE
INTRODUCTION
1.1. BACKGROUND TO THE STUDY
The term “composite” broadly refers to a material system which is composed of a discrete constituent (the reinforcement) distributed in a continuous phase (the matrix) and which derives its distinguishing characteristics from the properties of its constituents from the geometry and architecture of the constituents, and from the properties of the boundaries (interfaces) between the different constituents (Clyne, 2000 and lkechukwuka, 1997). Composite materials are usually classified on the basis of the physical or chemical nature of the matrix phase, e.g., polymer matrix, metal-matrix and ceramic composites. In addition there are some reports to indicate the emergence of intermetallic matrix and carbon-matrix composites (Surappa and Rohatgi, 1981). Aluminium is the most popular matrix for the metal matrix composites (MMCs). Aluminium alloys are quite attractive due to their low density, their capability to be strengthened by precipitation, their good corrosion resistance, high thermal and electrical conductivity and their high damping capacity (Whitehouse et al., 1991). Aluminium matrix composites (AMCs) have been widely studied since the 1920s and are now used in sporting goods, electronic packaging, amour and automotive industries (Skibo et al, 1988 and Donne et al, 1990). The unique thermal properties of aluminium based composites such as metallic conductivity with a low coefficient of expansion and high operating temperature and whose values can be tailored down to zero.
They offer a large variety of mechanical properties depending on the chemical composition of the aluminium matrix. The following reinforcements Al203, SiC, C,
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Si02, B, BN, B4C are usually used in aluminium matrices (lkechukwuka, 1997, Skibo et al, 1998 and Lloyd, 1999). As proposed by the American Aluminium Association, AMCs should be designated by their constituents: accepted designation of the matrix/ abbreviation of the reinforcement‟s designation/arrangement and volume fraction in % with symbol of type (shape) of reinforcement. For example, aluminium alloys AA6061 reinforcement by particulates of alumina. 11% volume fraction. is designated as “AA6061/Al203/11p” (Ikechukwuka, 1997, Rohatgi et al., 1988, Zhou and Xu, 1997). Particulate reinforced metal matrix composites (PMMC) are currently being used as structural components in many aerospace and automotive applications. The increasing demand for PMMCs is due to the unique mechanical properties achieved in the metal when ceramic particulates are used as reinforcement phases. PMMCs usage in other automotive applications include:
o Automotive and heavy goods vehicles.
o Braking systems, piston rods, frames, pistons, piston pins, valve spring caps.
o Brake discs, disc brake calipers, brake pads
o Accumulator plates.
o Military and civil air industries
Axle tubes, reinforcements, blade and gear box casings, fan and compressor blades, turbine blades, aerospace industry, frames, reinforcements, aerials and joining elements.
Particulate reinforced metal matrix composites (PMMCs) are currently being used as structural components in aerospace, automotive and industrial applications. Discontinuously reinforced metal matrix composites have received much attention because of their improved specific strength, good wear resistance and modified
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thermal properties unattainable in either of the starting (monolithic) materials (Ritnner, (2000), Wahab et al, 2009). These materials have emerged as the important class of advanced materials giving engineers the opportunity to tailor material properties according to their needs. Essentially these materials differ from the conventional engineering materials from the view point of homogeneity (Varajappa and Ghandrmohan, 2005). PMMCs combine the ductility and toughness of the metal matrices with the high strength and stiffness of the ceramic reinforcement to achieve properties unattainable in either of the starting materials. PMMCs often have high strength to weight ratios, which is an important consideration in weight sensitive applications. Other distinctive properties of PMMCs include good thermal stability and excellent wear resistance (Aigbodion, 2007). Dispersing small particulates (less than 1m) in a metal increases its strength, typically by Orowan type strengthening mechanisms. Traditionally high modulus ceramic particulates such as silicon carbide (SiC) and alumina (Al2O3) have been used as reinforcements purposely for stiffness enhancement, plus strengthening. It is however, known that other property benefits can be achieved by carefully controlling the matrix properties, the reinforcement properties, and the interface formed between them. 1.2 STATEMENT OF RESEARCH PROBLEM i. The demand for high level performance of the automotive connecting rod for rigidity, weight reduction (light weight) and ability to withstand tremendous loads puts conventional steel or aluminium alloy connecting rods to the limits of their material strengths particularly the effect of combustion gas loads in the combustion area.
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ii. The life span (service life) of the connecting rod is affected due to corrosive action of the combustion products. Abnormal combustion is a serious problem for connecting rods (Schreier, 1999).
Fig: 1.1. Typical Connecting rod (Schrier, 1999) To obtain optimum performance from composite materials, there is an advantage in selecting the shape and size of the reinforcement material to suit the application. It is apparent that different material types and shapes will have advantages in different matrices. For instance, silicon carbide whiskers have been particularly effective in toughening Al203 and Si3N4. Both silicon carbide whiskers and silicon carbide grit have been effective in increasing the modulus of aluminium alloys (Ikechukwuka, 1999 and Clyne, 2001).
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Thus researchers have worked out separately how to reinforce SiC, Al203 (i.e. carbides, nitrides and oxides) TiB2, boron and graphite into the aluminium matrix. By these reinforcements the composites have high densities and are also expensive. The ever-increasing demand for low cost reinforcement in a composite material, stimulate the interest towards utilization of by-products from industries as reinforcements. They are readily available and are naturally renewable at lower cost. 1.3 THE PRESENT RESEARCH The present research focus on the development of metal matrix/coconut shell ash particulate composite for automotive applications with particular interest in the connecting rod out of the numerous research problems. 1.4 AIM AND OBJECTIVES OF THE STUDY The aim of this work therefore is to develop a metal matrix/coconut shell ash particulate composite for automotive applications with particular interest in the connecting rod. The specific objectives are to: i) carry out characterization of the coconut shell ash, and use it with aluminuim alloy to produce MMC. ii) determine the physical and mechanical properties (such as density and porosity) of the developed composite and also study microstructure, and the various phases using the scanning electron microscope/energy dispersive spectrometer (SEM/EDS) and X-Ray diffraction meter (XRD) iii) study the corrosion properties of the MMC, and carry out wear test on the MMC, v). construct the connecting rod with the MMC, and test the performance of the rod
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1.5 SIGNIFICANCE OF THE STUDY The significance of this work is to further exploit the properties, characteristics and potentials of aluminium alloy/coconut shell ash in order to complement its existing areas of application, as well as to determine new areas of application particularly in the production of connecting rods. This research will add value to the abundant coconut shells in Nigeria for the production of metal matrix composites for the automotive and other industries, and reduce the environmental problems of disposal of the agricultural waste by open burning which leads to CO2carbon dioxide and methane emissions. The research will reduce the cost of reinforcement in metal matrix composites since coconut shells are available in large quantities and can be regarded as renewable products. The results that will be obtained in this research can act as a starting point for both industrial designers and researchers to design and develop MMC components using this agricultural waste in the production of automotive components, which will be a great benefit to Nigeria and the world at large. 1.6 SCOPE OF THE WORK Experiments will be conducted under laboratory conditions to assess the physical, microstructural and mechanical properties of the developed metal matrix/coconut shell particulate composite for automotive applications, with particular interest in the connecting rod. Experimental samples will be produced by the stir casting technique. The samples will be examined under the optical microscope, SEM/EDS and XRD to study the effect of particulate reinforcement on the mechanical properties of the composite.
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