Advantages of Carbon Fiber-Reinforced Composite Material - Coursework Example

Carbon fibre composites compared with traditional metallic materials. 1a Advantages of Carbon fiber-reinforced composite material Carbon fiber-reinforced composite material consists of fibers which exhibit high modulus and strength entrenched in the matrix with discrete interfaces between them. The combination of fibers and matrix create a blend of properties that cannot be obtained when the constituents acts alone. The fibers acts as the main load carriers, and the surrounding matrix keeps them in the desired orientation and location, protect them from damages like effects of moisture, and they also transfer the load. Thus, carbon fiber-reinforced polymers have a combination of modulus and strength which can be better than traditional metallic materials (Murray, 1997). Due to the low density of the composite materials the fibre components have high modulus – weight ratio and strength-weight ratio which makes them more superior to metallic structures. In addition, fiber-reinforced composite has excellent tolerance to fatigue damage, making it the main substitute for metals in applications which require weight considerations like automotive and aerospace (Pielichowski et al., 2005). Traditional metallic structures like aluminum and steel has isotropic nature, because they exhibit similar properties in all directions. On the other hand, fiber-reinforced composite has different properties depending on the direction of measurement, and thus they are anisotropic. This is because they have a fibre matrix ply which form layers of materials, such that all the fibres are parallel and they lie in longitudinal orientation. The anisotropy is influenced by fibre orientation in the matrix. Thus, anisotropy is high in composite materials which has fibre disposition, but it is lower when they are randomly oriented (Pielichowski et al., 2005). For this reason, the modulus and tensile strength in one directional orientation of fiber-reinforced material, is maximum in longitudinal orientation of the fibers. These properties are lower in any other direction, with its minimum value in transverse direction of the fibers. Multiply is formed by combining different plies with different orientations (Murray, 1997). The anisotropic characteristics, which can measure in terms of mechanical resistance and elastic properties, can create more opportunities for tailoring properties depending on the requirements. The design can be used for structure reinforcement in the direction of the main stresses, which increases the stiffness in the required direction and produce curved panels without more forming processes. For this reason, carbon fibre composites are five times stiffer than steel (Murray, 1997). Carbon fibre reinforce materials has excellent mechanical properties and has the same moduls and strength in the presence of heat. They produce structures with less co-efficient of thermal expansion and poor thermal conductivity. They can be used in applications with high temperature with less effect since they retain their strength at elevated temperatures. In fact they retain strength at high temperature of upto 10000C (Bhandari, 2010). Carbon fibres are also less affected by moisture or a variety of bases, acids and solvent. They exhibit mechanical and physical feature, enabling their incorporation of these fibre to get specific properties. Finally, carbon reinforced fibre is relative simple(Bhandari, 2010). 1b The effects of the high production rates needed for vehicles on the use of the composite materials Composite materials have been produced and used in automotive industry for decades since 1953, but they have been produce in low volume because of the high cost of production compared with the conventional materials like steel (Bhardwaj, 2014). The main reasons behind the production of polymer composite materials have been the reduction in weight and a range of opportunities it offers, as well as resistance to corrosion, anisotropy, mechanical properties and design flexibility. In spite of all these advantages, the production of composite materials has been hindered by high cost of production and slow production rates. For example, the cost of producing composite materials is ten times higher than producing the conventional materials like steel. Thus, the target focus is to produce low cost fibres for applications which require stiffness or tolerance to damages (Burchell, 1999). The choice of fabrication techniques is dependent on the technical requirements and the cost of materials to be used. In order to ensure economic production, it is necessary to apply technique with high throughput. This can be achieved through integration of sections and using methods which takes less time (Vasiliev & Morozov, 2007). Composites autoclave molding process is mainly used in aerospace industry. In this process, resin pre-impregnated oriented woven cloth or plies that have been cured partially are used. Pre-pregs are heated and pressed on the former in in autoclave with high temperature and pressure (Burchell, 1999). Therefore, the air is squeezed out of the cloth, and the resin will flow between the fibre and thus create a consolidated molded material. The main disadvantage of this process is that the pre-preg has to be cooled to stop the resin from flowing off. Different layers of pre-preg plies are placed on the surface with predetermined fibre orientation up to the desired thickness, before covering with silicon or vacuum bag, fabric and release film (Bhardwaj, 2014). A vacuum is created by drawing the air out of the bag and the tool is heated under high pressure and temperature to treat resin. Multiple demolding process cycles are done by wrapping the laminate and creating a vacuum at some layer interval so as remove excess air between the plies. This not only reduces delamination in the layers and controls the thickness size. Good mouldings in curing are achieved through application of hydrostatic pressure and regular demolding cycles. The production of autoclave molding is low because demolding cycles manual lay-up and bagging require a lot of labour and consumes more time. In addition, the initial investment for autoclaves is quite high, and it does limit its use to justifiably large investment (Elmarakbi, 2013). To achieve higher productivity, composites structures oriented properly in the molding tools during preforming stages. However, this will result in high cost of labour, long cycles and low production. Some processes are applied in preform such as multiple plies vacuum, braid reinforcement on molded core and robotic application so as to improve the performance (Elmarakbi, 2013). The focus of high productivity for the applications is to reduce the cost of automotive structures from light weight composite materials, using composite process in repetitive, fast, environmental friendly and cost effective manner. This shortens the cycles times and reduces labour cost, making them more competitive (Bhardwaj, 2014).  Vacuum Bag/Autoclave Pre-preg Layup for Autoclave Cure 2. The Competitive Nature of Composites in the Automotive Industry Carbon fibre materials have to be cured in mold to produce stiff and light weight component, but with drawbacks. The cost of producing the components is high because the mold takes a long time to cure fully in the autoclave. Some manufacturers are moving away from carbon fibre components due to long processing times needed for high integrity carbon fibre composite components. It takes a long time to manufacture carbon fibre material making it uneconomical as the production volume becomes too low (Pilato & Michno, 1994). The design of vehicles is expected to produce and sell large volume than the old design. This can be done by substituting the material used or by doubling the cost of production so as to run in parallel. Although multiple molds can be made at a time, it is very expensive and consumes more space and time. In addition, the method of manufacturing of carbon fibre is expensive and takes more time to complete a cycle, which results in low production volume, but steel is produced by setting dies in the press and whacking out one every few seconds taking less time in a cycle. In some cases where excess materials are used, the high volume fibre construction may not produce the expected weight saving components (Elmarakbi, 2013). Vacuum bag can be used as an alternative to autoclave, but it is also very expensive technique that applies pressure to the component by creating a vacuum bag around the mold loaded with pre-peg carbon. The pressure is not high enough so as to consolidate resin fully into fibre, to produce high level of quality component for an automotive. It may require expensive and labour intensive approach to achieve the desired potential that the composite offer. Since the efficient way of manufacturing carbon fibre has not been fully exploited, many companies have not seen the advantage in terms of profit, of replacing the conventional metals with carbon fibre. References Bhandari, V. B. (2010). Design of machine elements. New Delhi: Tata McGraw-Hill. Pielichowski, K., Njuguna, J., & Rapra Technology Limited. (2005). Thermal degradation of polymeric materials. Shawbury: Rapra Technology. Murray G., (1997). Handbook of Materials Selection for Engineering Applications, MECHANICAL ENGINEERING, CRC Press Wu, H. C., & Institute of Materials, Minerals, and Mining. (2006). Advanced civil infrastructure materials. Boca Raton, Fla: CRC Press. Bhardwaj B.P., (2014)The Complete Book on Production of Automobile Components & Allied Products, Niir Project Consultancy Services Pilato, L., & Michno, M. J. (1994). Advanced composite materials. Berlin: New York. Vasiliev, V. V., & Morozov, E. V. (2007). Advanced mechanics of composite materials. Amsterdam: Elsevier. Burchell, T. D. (1999). Carbon materials for advanced technologies. Amsterdam: Pergamon. Elmarakbi, A. (2013). Advanced Composite Materials for Automotive Applications: Structural Integrity and Crashworthiness. Hoboken: Wiley. Read More