Abstract

Automotive Engineering friction based components are usually produced from asbestos material which is not environmentally friendly. The brake pad was formed with periwinkle shell, palm kernel and coconut shell, cashew nuts powder as core materials, epoxy resin and harden eras binder and carbon as fiber brace, copper, zinc aluminum and cashew nut shell served as abrasives with filler from shoe rubber dusts. Ten different groups of samples with various grit sizes and different percentage compositions were taken to produced 20 sample of the brake pads. The materials were grinded using hammer Mill, sieved with sieving tray of 425 μm, 850 μm,1000 μm and 1100 μm mesh sizes to determine the micro structure of the particles sizing. The material was weighed out with digital weighing scale to have the correct mixture ratio that contains all the required constituent elements. Test results reveal that Sample A, with a smaller grit size of 425μm grits size of palm kernel, 1000 μm grit size of cashew shell, 1000 μm grit sizes of periwinkle and 425 μm grit sizes of coconut with other mechanical properties found in Table 2 gave the desired mechanical property, when compared to the conventional brake pads which serve as control.

1. Introduction

Brake plays a vital function in automotive to reduce the vehicle speed or stop it absolutely. This is achieved using frictional grips of surfaces in contact. The robbing effect is what causes the stop or speed reduction. At the application point of brake, there is friction generated at the disc and brake pads, causing the vehicle speed to drop by transforming energy kinetically to heat. The brake pads instantly assimilate heat, not wear speedily and resisting higher temperatures. Usually two pads are contained in the brake callipers, the rotor facing the friction surfaces. ¹ The pad material maintains high rubbing coefficient with the disc, not break in a manner that the rubbing coefficient with the brake disc is eroded at raised temperatures showing a stable and consistent rubbing coefficient with the disc. As technological advances, increase safety is of interest, more specification were forwarded on the eco-friendliness of brake systems, intelligence, security plus mechanical devices operating comfort. This is imperative for Engineers to form novel brake’s rubbing materials with good qualities and explore their mechanism of rubbing and wear in braking. To eliminate pollution in our environment, studies have become a much more serious business to finding a better and standard ways of sourcing materials free from contaminants for the proper production of brake pads. In years before now, asbestos was prominent in brake pads manufacture. In recent time, the prime foundation material for forming brake pad/lining is asbestos fiber, it is utilized by industry, primarily in construction and friction materials. Broadly, pad consists of binder, reinforced fibers, friction additives and fillers. These are mixed or blended in various ratio and material of pads is created using different techniques of production. The mechanical strength of the rubbing material is increased with the presence of reinforced fibers. Aim of binder is maintenance of the pads structural integrity subjected to mechanical and thermal stresses. The components of a brake pad are held together by binder and to hinder its elements from crumbling. Brake pad have fillers for the purpose of enhancing manufacturability plus reduction in overall pad cost. Drum and disk (brake) are major types of friction brakes ². Multiples of materials and their variants are found in components of brake. Asbestos is known with minor engineering features that presents it as suitable for inclusion in brake liners, that made it the most sort after filler material till 1989. Its inclusion is deliberately ignored due to health implications ³.

The materials engineer is challenge with importance of forming a substitute of brake pads with no asbestos friction materials. Asbestos is known to form carcinogenic signs on health of man. It aroused the study of materials such as waste from agricultural produce, which are rising as novel and little expensive materials in the pads form with commercial potential and acceptability environmentally for brake pad that have needed features. We have semi metallic, organic, metallic pad materials. According to ³, Herbert Frood is linked to invention of the initial material for brake lining in 1897. This was cotton-based material with solution of bitumen and found in wheels of wagon. Studies across the world today have their focus on techniques of using either agricultural or industrial wastes as unprocessed materials sources for the industry. The using of wastes would not only become economical, it may attract global exchange earnings plus pollution control ⁴. Coconut shell as a waste from agricultural produce is found in huge quantities across the tropical countries. Particles of coconut have notable role in the automotive industry due to its quality of hardwearing and hardness, high acoustic resistance, zero toxic, mothproof, microbial fungi resistance degradation, and low combustible. In recent times, the core material for production of brake pad/lining systems in brake system is asbestos. Despite the fantastic features, asbestos are withdrawn from applications with chances of respire and taking in dust, due to cacogenic features.

Brake grips have been seen historically to be in these stages: wooden block, mechanical drum, expanding internal shoe, hydraulic, disc, auto luck, four wheel, power assisted, self-adjusting and automatic brakes. The materials are usually grouped as binders, friction modifier, abrasives, lubricants, filler and reinforcements. The binder has some features elastic in nature to moves the load to fibres, have mild strength at a high temperature, have low temperature capability, show perfect chemical resistance, process easily to final composite shape, and dimension stability so as to retain shape ⁶. Some additives that are frictional may be freely referred to as fillers by some manufacturers depending on quantities. Popularly lubricants used are graphite and various metal Sulphides. Graphites are utilized based on its ability to generate a layer of lubrication on the resisting counter friction material instantly ⁷. This layer that is self-sustaining ensures friction coefficient stability. The graphite utilized in brake friction materials can either be of synthetic or natural origin and can appear in different forms. Graphite in form of flake possess enhanced lubrication characteristics ⁸, while graphite in form of powder effectively dissipates more heat generated during braking ⁹.

Abrasives maintain the clean state of surfaces mating and the buildup of films of frictional form is controlled. In addition, it raise friction, mainly when starting a reduction; simply put, it raise “grip and bite”. Friction materials abrasives raise its frictional coefficient at same time raising the counter face material wear rate. Oxides of Iron are removed from the opposing friction material plus surface films undesired and formed during braking. Materials with greater abrasive compositions show huge friction coefficient variation, leading to braking torque instability. Fillers maintains the total friction material composition; some have auxiliary attached functions. Brake pad have fillers added to enhance its manufacturability and minimize the brake pad total cost ¹⁰. Aim of fibers reinforcement is for friction material mechanical strength. Recently, studies points the braking load is held by tiny plateaus that increased above the friction material lowlands surrounding ¹¹. These plateaus are created by the fibers circled by compacted softer components. The need for the bracing fibers in friction material can never be lowly estimated. Varying mixture types of reinforcing fibers with properties complementing are utilized in friction material. Over time, the constituents of the brake grips produced in this research have been a concern as regards to its polluting tendency in Southern Nigeria. The materials used were obtained locally from processing plant, mills and farms located within southern Nigeria and the material ensures continuity and constant availability, as they are local waste materials. They are non-renewable agro resources whose needs are essential in the society and their uses cannot be overemphasized. These materials are waste products and thus they are readily available at all times and at cheaper and affordable prices. The use of these materials enhances the recycling of waste, as they are waste products and thus promotes a clean and healthy environment. The aim of this research work is to sustain a friendly environment, wealth creation, eliminate asbestos use and have a readily available brake pads produced within the environment thereby reducing material waste.

The results in this research show that the local base materials has comparable features to that desired for use as brake pad material to replace asbestos utilized in brake pads production.

2. Material and Method

The materials utilized for forming of the brake pads were selected due to availability, which include palm kernel, periwinkle, coconut and cashew nut shells as core material, binder materials was epoxy resin, fibre reinforcement with carbon, cashew nut as lubricant, aluminium, abrasives utilized were zinc and copper, filler was from shoe rubber dust. List of equipment used are; Wooden Block, Digital Scale, Hammer Mill, Venire Caliper, Sieving Tray, Hardness Tester, Compression Testing Machine, Friction Plane Apparatus, Muffle Furnace, Rockwell Hardness Tester, Abrasive Tester, Disc Brake Test Apparatus. The process involved was categorized into three (3) sections, namely Raw Materials Characterizing, Preparation of Samples, and Characterizing of Products.

Figure 1 indicated the flow in brake pads development using local sourced material as raw material. The processes involved are listed in order of involvement, raw material acquisition, crushing and sieving, mixing, compaction, curing and obtaining the desired product. Upon getting the desired shape, compression, hardness, density and wear tests were carried out for comparison.

The various materials used for this fabrication such as palm kernel shell, cashew shell, coconut shell and periwinkle shell was sourced within southern Nigeria and then processed to generate our major raw materials which are their slags. The materials were subjected to several procedures and processes to ensure an efficient and effective brake pad formation. The procedures include debris and contaminant removal, washing, sun drying, crushing, sieving to different particles sizes, weighing to ensure required percentage composition, mixing of measured composition percentage, mold preparation, compacting and hot press curing.

3. Results

4. Discussion

It is observed that the composite material with the highest coefficient of thermal conductivity is a good conductor of heat. Samples A, B, C, D and E are excellent conductors of heat while F, G, H, I and J are medium conductors. The control sample had a coefficient of thermal conductivity of 0.2278 w/mk while two samples (A and B) from the composites had 0.2283 W/mk and 0.2280 W/mk, which is a much better conductor than the Control.

The various samples of brake grips were presented to compressive force, loaded continuously till fracture occur, and shows bar chart of compressive strength and hardness of various sample in relation to the control sample. Sample A observed to have the highest compressive strain of 503 kgf and a hardness strength of 78 kgf when compared to the control sample which has a compressive strength of 490 kgf and hardness of 67.3 kgf as found in Figure 2. Figure 3 show the impact strength and wear rate of the various sample when compared to control sample, it was observed that sample A has high impact strength of 0.880 J/s and wear rate of 0.11 mg/m while the control sample has an impact strength and wear rate of 0.855 J/s and 0.14 mg/m. This suggest that a mixture composition of sample A as shown above gave a better test results compared to the control sample.

5. Conclusion

The design and forming of an automobile brake pad with indigenous available materials have been carried out. Shell of Periwinkle, Shell of Cashew, Coconut and Palm Kernel were sourced within for the work and were utilized as raw materials , the local base materials were crushed using harmer Mill and was sieve into various grain size using sieve mesh of 425 μm, 850 μm, 1000 μm and 1100 μm to determine the microstructure of the particles, epoxy resin and epoxy hardener was used as material for binding, carbon as fiber bracing, copper, zinc and aluminum were utilized as abrasives and filler obtained from shoe dust. Extract from the review of the conducted experiment, showed that the rubbing co-efficient of the brake pad material ranged between 0.65 - 0.86, hardness 48.4 kgf - 78 kgf, bonding strength of 25-28 Kg/cm², wear rate between 0.107 mg/min - 0.18mg/min, impact strength of 0.820 J/s to 0.880 J/s, density of 0.9 kg/m³ to 1.3 kg/m³, water absorption rate of 0.4 % - 0.8 %, oil absorption rate of 0.3 % to 0.6 % and coefficient of thermal conductivity of 0.2231 w/mk to 0.2283 w/mk as compared to the control sample which is the acquired conventional brake pad material that has compressive strains of 490 kgf, hardness of 67.3 kgf, bonding strength of 25-27 kg/cm, density of 1.2 kg/m³, impact strength of 0.855 J/s, wear rate of 0.14 mg/m, water absorption rate of 0.6%, oil abortion rate of 0.45 % and coefficient of thermal conductivity of 0.2278 w/mk. From the results, the static friction coefficient obtained is between 0.5416 - 0.8785 while the dynamic friction coefficient is between 0.4 - 0.657 when subjecting the brake pads to various sliding mass, while conventional brake pad produced in Nnewi which serve as a control gave a static friction of 0.8 and a dynamic friction of 0.659. From the desired morphology and mechanical properties, the research output presented Sample A, with a smaller grit size of 425 μm grits size of palm-kernel, 1000 μm grit size of cashew shell, 1000 μm grit sizes of periwinkle and 425 μm grit sizes of coconut with other mechanical properties listed on Table 2, gave the best properties therefore it is deducible that this material can be used on mini buses brake system. The results above show that the local base materials which are Periwinkle, Cashew Nut Shell, Coconut Shell and Palm-kernel shell has features comparable to that desired for use as brake pad material to displace asbestos utilized in manufacture of brake pads since it show better results for manufacturer of brake pad.

Acknowledgments

We wish to acknowledge effort of two students Odey Anthony and Sandra Egwuekwe, who helped in this work. Also we appreciate the Chief Technologist of Mechanical Engineering Workshop of Federal University of Technology Owerri Engr. F. Onyeneke. Special appreciation to the management of Federal University of Technology Owerri, the Department of Mechanical Engineering and others who helped in many ways.

References