Carbon Fibre Composite Materials on Vehicles - Coursework Example

Carbon Fibre Composite Materials on Vehicles Introduction This research paper gives a comprehensive account of the carbon fibre composite materials considered in manufacturing automotive by exploring ten published articles in three sections. In the first section, it discusses the advantages of carbon fibre reinforced polymers with respect to their mechanical and specific properties in replacing the traditional metallic in automotive body structural applications. This section also includes issues associated with anisotropy and how such issues can be addressed in relation to the resulting effect on mechanical properties. The second section explains the issues of how the high production rates needed for many standard classes of automotive correspond to the use of such composite materials with respect to their processing characteristics. The third section concludes the paper by giving reasons as to why some niche vehicle manufacturers are currently moving away from carbon fibre components for their medium production volume automotive structures because of their long processing time needed for a high quality carbon fibre composite material, and it is to this that I now turn. Advantages of carbon fibre composite in comparison with traditional metallic. Jones et al. (2011) argues that, for the materials to be accepted in automotive industry it has to possess suitable properties and characteristics before being approved. Some of these properties are as a result of laws and legislation with the environmental and safety concerns and majorly the satisfaction of the customers taste (Chung 1994). Due to these considerations, the use of composites in transport industries as alternatives to traditional materials has been adopted due to the impressive mechanical properties and their low densities which promote their structural applications where lightweight is considered critical to final design; this ensures a higher performance for a given weight leads to fuel savings. Quality strength-to-weight and stiffness-to-weight ratios can be achieved by composite materials, as this is always expressed as strength divided by density and stiffness divided by density (Elmarakbi 2014). Initially in the automotive industry there was use of metals such as aluminium and steel which were of high densities i.e. aluminium has 2.7g/cm3 and steel 7.8g/cm3 which resulted into low speed and high fuel consumption due to their weight (Evans et al. 2003). These put the automakers into task to develop lightweight materials with preferably high strength of stiffness and corrosion resistant. To achieve this there was need to combine different materials to enable isotropy since these qualities could not be found in just one material hence the composites arose. It has been estimated that for every 10% of weight a vehicle’s total weight, fuel economy is improved by 7%. It also implies that for every kilogram of weight reduction there is a bout 20kg of carbon dioxide reduction (Lovins 2011). Another important factor to consider as far as automotive production is concerned is awareness for the environment. This results into considerations of recycling and life circle. Issues such as ‘protection resources’, reduction of carbon (iv) oxide emissions’ and ‘recycling’ are major targets of considerations. Like in European Union legislation implemented 2006 strictly emphasize on the significant percentage of the vehicle should be re- used or recycle which aims at reducing the amount of waste produced from vehicles when they are scrapped (Lovins 2011). These vehicles are considered hazardous waste to the environment until they have been fully treated. This would mean that the last owner of the vehicle must be issued with the certificate of destruction for their vehicle for them to dispose them free of charge. This implies that the vehicle manufacturers and importers must cover the cost of the free take-back system (as cited in Hollaway 1994). With the composite material put in place, it’s easier to achieve smooth aerodynamic profiles for drug reduction. Complex double-curvature sections with smooth surface can be made in one manufacturing operation as opposed to the traditional automotive industries hence production cost is reduced (Evans et al. 2003). Production rates for automotive and their processing characteristics Currently, the consideration of manufacturing process depends upon the required rate of production (Fraden 2010). As a point of consideration, Dunn (1997) argues that, a typical truck application may have a volume of between 5,000- 20,000 parts in a year, while for cars it may be between 80,000- 500,000 parts in a year. Other aspects that must be put into consideration are the tooling costs, scrap manufacturing and cycle time. Tools for composite manufacturing are much cheaper than tools for sheet metal forming since composite processes are single operations; one mould, while sheet metal forming needs five-six separate tools per component line (Evans et al. 2003). The savings in tool cost are so influential at low production volumes. The only available composite production processes for higher production volumes are short composite fibre reinforced thermoplastic injection moulding and bulk moulding compound procedures (Chung 1994). However, these processes are not applied in structural applications. With the improvement of long fibre reinforced thermoplastic application process, high volume will be closer to what can be regarded as ‘structural’ fibre reinforced polymer. The major benefits of injection moulding are that it produces little amount of scrap and that it has short cycle times; 90 seconds for a dashboard moulding (as cited in Evans et al. 2003). Currently there are few procedures for average volume composite production. Compression moulding considering sheet moulding compound or glass mat thermoplastic are the most normally used. The two have become highly automated and currently used for cars and trucks with cycle times in fewer periods (Hollaway 1994). Another process for medium volume composite production is the resin transfer moulding (RTM). It can be applied in structural applications and it’s of best interest because of its potential automation, better trustworthy and better achievable mechanical properties (as cited in Fraden 2010). The surface completion of RTM sections is also beneficial. The limitations of RTM are high costs of tooling, high levels of the composite material waste and very long cycle times. The direct long glass fibre thermoplastic (D-LFT) process is also important to mention, as it combines better structural characteristics with finish process automation. Composite production processes such as fibre braiding and fibre placement have also become automated since they are beneficial for niche and low volume production (Beukers 2005). It’s therefore confirmed that there is no doubt that composite manufacturers are struggling to become very competitive in regards to production for the automotive industry. Other considerations are further development in surface finish and paintability. In particular, there is a requirement for the clarification and improvement of standards and measures for surface quality (as cited in Ashby 2005). Arguments of the niche vehicle manufacturers about carbon fibre components. This section answers the question as to why some niche vehicle manufacturers are currently not regarding the carbon fibre components as the best alternative for the construction of automotive. With the volume of traffic rising up on today’s roads there is a universal pressure on the automotive manufacturers to come up with cleaner and more effective vehicles. One of the major obstacle facing vehicle manufacturers is the balance between environmentally friendly vehicle and the level of comfort, safety and price anticipated by the consumer (Chung 1994). Niche vehicle manufacturers are making more effort to maintain this balance by researching on the technology to discover lightweight materials for lean weight designs since carbon fibre composite materials poses a number of challenges to the manufacturers, and it’s from this that Ashby (2005) turn. Processing poses the biggest challenge to niche vehicle manufacturers since it consumes too much time and therefore leads to delay of the entire construction period (Dunn 1997). As a point of consideration, processing in this section is defined as the work done after the composite part is manufactured to give the composite part a final finish and size, and join several parts together (Elmarakbi 2014). Machining being a significant stage of processing, its damage is inevitable if methods of material removal are applied to machine composites. The destructions can interfere with the mechanical properties of the composites. The excellence of the machining depends on the cutting speed and the feed rate (Elmarakbi 2014). Tool wear is another cause of machine destruction to the composite part. It happens when the cutting edge of the machine is damaged so that the initial cutting geometry is changed. Abrasion and micro chipping confirms the reason as to why tool wear occur when machining fibre-reinforced plastics (Evans et al. 2003). The tool becomes less efficient in material removal and in generating better quality machined surface. The cutting edge can be minimized, the tool forces, power utility and the cutting temperature rises, the surface completes degrade, reduction of part dimensional accuracy and possibility loss of productivity can take place because of tool wear (Chung 1994). Delamination being another step under machining is defined as the process by which different layers separate from each other (Dunn 1997). It come out as a major issue when machining fibre reinforced plastics and a good amount of time and cost can be saved if delamination could be avoided. Delamination can move at different processes; milling and drilling (Beukers 2005). Machining fibre reinforced plastics causes tool wear and brings out a major reason for the occurrence of delamination. A sharper tool reduces the risk of delamination, because the fibres are cut in a clean way. Delamination completely affects the structural integrity and long-term trustworthy of the machine component. It’s the most serious problem relating to the machinability of drilling fibre reinforced plastics (Fraden 2010). Drilling operations involves a thrust force that acts normal to the ply and tends to separate the layers in a laminate through interlaminate cracking. Delamination during the process of drilling occurs in two ways, by peeling up the outer layer of the laminate or punching out the uncut layer near exit. The top layer of the composite part is peeled up when the thrust force is sharply reduced and mechanically peels up the work piece (Lovins 2011). Joining composite also come as another stage in processing fibre composite materials. Composites can be joined in different ways by using mechanical fasteners, adhesive bonding and welding. Welding is applied in thermoplastics and challenge regarding this is therefore not considered. When dealing with mechanical fasteners, bearing, net tension and shear-out are most common possible joint failure modes which may happen in composites; this is according to Beukers and Hinte (2005) and Ashby (2005).These challenges occur because of comprehensive stress in the material that are close to the contracting bolt surface (Evans et al 2003). Fraden (2010) shows bearing, tension, shear-out and cleavage as challenges caused by mechanical joining. There are three types of fatigue destruction around the bolt hole: hole wear, destruction in the contact surface of the composite and the growth of delamination around the bolt opening caused by drilling (Hollaway 1994). Other challenges related to the bolt opening are fastener pull through and fastener failure (Dunn 1997). The joint geometry in comparison with the laminate lay-up is basically affecting the occurrence of failure modes, although the type of fastener can also interfere with the occurrence. Galvanic corrosion is also one the common problems with composite fibre plastics under processing. Galvanic corrosion occurs when a metal is degrading because of electrochemical reaction with its environment (Fraden 2010). Galvanic corrosion can be costly to repair since it requires drilling of new holes and installation of an oversized fastener of the right material. May lead to serious structural failure but if the materials are well selected, corrosion can be avoided (Jones et al. 2011). Galvanic corrosion can also be avoided by utilizing a titanium sleeve as a separator, but humidity may provide a bridge around the sleeve and corrosion may occur (Chung 1994). Issues related to tension and cleavage tension, shear-out, adhesive bonding and adhesive creep, surface treatment are also considered as major drawbacks to the processing time hence confirming the reasons as to why some niche vehicle manufacturers are currently moving away from fibre composite materials. Bibliography Ashby, M. F. (2005). Materials selection in mechanical design. Amsterdam, Butterworth-Heinemann. http://app.knovel.com/web/toc.v/cid:kpMSMDE014. Beukers, A., & Hinte, E. V. (2005). Flying lightness: promises for structural elegance. Rotterdam, 010 Publ. Chung, D. D. L. (1994). Carbon fiber composites. Boston, Mass, Butterworth-Heinemann. Dunn, B. D. (1997). Metallurgical assessment of spacecraft parts, materials and processes. Chichester [u.a.], Wiley [u.a.]. Elmarakbi, A. (2014). Advanced composite materials for automotive applications: structural integrity and crashworthiness. http://dx.doi.org/10.1002/9781118535288. Evans, A., Mortensen, A., & Sanmarchi, C. (2003). Metal matrix composites in industry: an introduction and a survey. Dordrecht [u.a.], Kluwer. Fraden, J. (2010). Handbook of modern sensors physics, designs, and applications. New York, Springer Verlag. http://public.eblib.com/EBLPublic/PublicView.do?ptiID=666935. Hollaway, L. (1994). Handbook of polymer composites for engineers. Cambridge, Woodhead in association with the British Plastics Federation. Jones, I. A., Middleton, V., & Owen, M. J. (2000). Integrated design and manufacture using fibre-reinforced polymeric composites. Boca Raton, Fla. [u.a.], CRC Press [u.a.]. Lovins, A. B. (2011). Reinventing fire: bold business solutions for the new energy era. White River Junction, Vt, Chelsea Green Pub. Read More