Chapter 7 Chapter 7 Conclusions and Future Scopes
3.5 Summary
ratio range 2-75, the reinforcement effect is observed to be affected by the volume fraction of the filler materials (Figure 3.14(b)).
Similar to the analysis carried out as shown in the Figure 3.13(c), the modulus reinforcement versus elastic modulus of all the composite samples show the linear relationship which is presented in the Figure 3.14(c). The slope of the straight lines of 5%, 10% and 15% cement filled composites are approximately 89º, 88º and 87º respectively. This signifies that for each 5% cement particles increment, the slope is decreased by 1º.
Chapter 4 Design and Fabrication of Composite …
Chapter 4
Design and Fabrication of Composite Material Spur Gear 4.1 Introduction
The demand for seeking alternatives to metallic gears in industry has led to the development of composite material gear. In this work, efforts have been given to develop low cost composite material spur gears using cheap materials i.e., polypropylene as matrix and cement as filler materials. Till date, metallic gears are mostly used in automobiles and industrial applications for their advantages such as durability, availability, smooth workability and reliability on performance. Although, disadvantages such as cost, high wear, more weight to power consumption limits usages of metallic gears in light scale (duty and weight) device applications. To amend these problems, metallic gears can be replaced by composite gears as the latter have certain advantages such as cheaper than metals, less weight to power consumption, durable, ease of processing and fabrication. Past researches show that dramatic enhancement and improvement in mechanical properties achievable by varying small amount of filler particles concentration. The resulting mechanical properties of the composites are closely related to the microstructure achieved in processing of these materials. The mechanical properties of polymer composite depend on the filler-matrix material properties, matrix-to-filler interface and orientation of the filler materials and hence the properties of the end product made govern by the composite used. Luo and Daniel, (2003) has shown, higher composite modulus can be achieved for randomly oriented filler composite by controlling and maintaining high dispersion rate. Mechanical characteristics of the material mostly depends on the microstructure and the strength of the bond between the filler- to-filler directly or filler to filler via matrix (Chabert et al., 2003). Maleic anhydride (grafted polypropylene; non- polar nature) is mostly used for attaining homogeneous dispersion of filler in the polypropylene matrix and to ensure proper bonding between the polypropylene matrix and filler materials (Raka et al., 2009; Gutiérrez et al., 2010; Fung et al., 2003).
The temperature dependent dynamic parameters like dynamic modulus, storage modulus, loss modulus and loss factor provides knowledge of relations between the polymer matrix and the filler. Even though, it is observed that failure of the composite depends on the percentage of filler materials incorporated into the matrix, however, most of the cases, the high percentage of filler materials decreases the ductility of the materials (Sohn et al., 2003).
TH-1430_09610309
Until now, huge progress has been made in forming micro/meso scale devices using the methodology and materials such as gears adopting molding, electroforming processes using electro-platable metals, alloys and poly-methylmethacrylate (PMMA) (Sun et al., 2009). The choice of composite materials applications in fighter aircraft was perceived by a need to reduce weight and to improve strength, reliability and maintainability suitable for aerospace applications. The F-22 fighter aircraft has demonstrated the feasibility and benefits of introducing processes such as resin transfer molding (RTM) to improve the affordability of composite materials in combat aircraft applications. Further, these composite materials not only reduce the weight but also possess excellent characteristics of corrosion and fatigue resistant. In addition, significant contribution can be achieved by designing composite materials which proves superior cost-effectiveness compared to conventional metals (Deo et al., 2001; Anon, 1999). A composite landing gear component for a fighter aircraft was developed as replacement of a steel component using resin transfer molding (RTM) technique for fabrication of structural components. The objective was to achieve a weight reduction of 20% and a cost reduction up to 15% (Thuis, 2002).
Further, past researches show that few works have been carried out to evaluate the dynamic mechanical properties of the composite materials used for fabrication of gears. In addition, few works deal with the failure analysis and the resulting topographical structures of the composite materials. This motivates to explore the grey areas exist on design and development of low-cost nonmetallic mechanical parts such as gear suitable for lightweight industrial application. Thus, it is relevant to try very inexpensive materials such as polypropylene and cements for design and development of composite materials and finding suitable applications of it. The particle size distribution of Portland cement particles is in the range of 0.1 to 100 m and the aspect ratio (L/W) i.e. length/width ratio varies between 1.27 - 1.46. A literature has been added into the texts, where much more in-depth analysis has been made on particle size distribution (PSD) and particles shape (Holzer et al., 2010). In this work, a new type of polymeric composite gear is fabricated using fly ash based cement particles as a reinforced material into polypropylene matrix followed by injection molding process.
The main objectives of this work are:
(i) Fabrication of a low cost composite material spur gear alternative to metallic gear (ii) Experimental evaluation and optimization of compositions for gear material and tooth performance analysis
Chapter 4 Design and Fabrication of Composite … Composite gear materials of three weight percentages of fillers are prepared and tested under dynamic load to evaluate the mechanical properties. Morphological analysis is carried out by scanning electron microscope (SEM) and field-emission SEM (FE-SEM) to investigate the topographical features of the fractured surface and deformed gear tooth, bonding between fillers and the matrix, dispersion and failure mechanism. Further, dynamic mechanical analysis (DMA) has been carried out to study the viscoelastic properties of the composite and the effect of temperature on it during loading. The experimental study and obtained results are instrumental to select the right combination of constituent materials for fabrication of the proposed gear. Gear tooth performance is evaluated by using Instron universal machine applying direct load on the tooth and also fatigue testing the gears tooth under dynamic load.
The experimental study and the results indicate that the developed gear is suitable for academic and industrial application. In addition, a theoretical model has been developed following the Hertz contact theorem that describes the stress profile along the tooth contact region of two meshed gear.