Abstract
This paper answers two different questions with regards to carbon fibre reinforced polymers. The first question discusses the advantages of carbon fibre reinforced polymers with respect to their mechanical & specific properties in replacing traditional metallics in vehicle body structural applications. In the second question, the paper addresses how high production rates required for many standard classes of vehicles correspond to use of such composite materials. It is done with respect to their processing characteristics. This is important considering that such materials are supplied in the form of pre-preg that must be vacuum bagged and autoclave moulded
Question 1a
Recent proliferation in the use of plastics reinforcement with carbon fibre in load bearing structures of automobiles is a great way to reducing fuel consumption and the weight of the vehicle. Carbon fibre reinforced polymers are not widely used as metals but their use is becoming popular with many manufacturers. The materials have found a wide range of applications in not just the automobiles but also in construction and aerospace. It is majorly due to their specific stiffness and strength, as well as lightness in weight. Carbon fibres also have the other advantages that make their use preferable in automobiles. The materials have a tensile strength, which is six times greater than metals. Such property is important in structures that are exposed to excessive force in the automobiles. Carbon fibre reinforced structures have improved tensional stiffness and high impact properties that make them function better in areas of high impact in a vehicle. In addition, the material has a higher rate of up to 60% of the ultimate tensile strength and it allows the polymers to endure fatigue (Ghassemieh, 2012).
CRFPs also have lower embedded energy when compared to metals. Such property is essential especially where the energy from the automobile engine is absorbed by the metal reducing its force and momentum. The low energy embedded is also important in hot weather conditions where metallic automobile uses air conditions to cool the inside of the automobile. CRFPs are also less noisy during operation and have lower vibration transmission when compared to metals. It is difficult to design metals into some shapes. It may take some time to be achieved and is also very expensive. CRFPs are easier to design into different shapes in relation to the needs and complexity of the design. The materials are more versatile, thus allowing easier, less expensive and faster design into different shapes. Compared to metals, CFRPs are more durable as they have a lower rate of wear and tear compared to metals. They also demonstrate excellent impact and environmental resistance. Thus, the materials are less expensive to maintain (Elmarakbi, 2013).
The anisotropic nature of carbon fibre reinforced polymers is a property that can cause a decreasing of fatigue endurance level of these materials. The anisotropic conductivity of these polymers also affects the unidirectional conductivity of the materials that is a part of the important specific property. To reduce the effect of anisotropy, the designer can exploit the electromagnetic behaviour of the polymer to enhance the automobile performance in highly fatigued areas. The unidirectional carbon fibre reinforced polymers when laminated can act as conductors in parallel E-field and dielectric in perpendicular E-field. Such understanding should help the designer of the material come up with carbon reinforced polymers that meet the fatigue rate of the automobile (Kelly, 2004).
Question 1b
Composite materials are not yet widely used in the automobile industry. However, there are many opportunities where advanced composites can be put into commercial use in automobile. For instance, in specialty vehicles that require small quantity of composite materials, they are already used to demonstrate the capabilities of CFRP. The composite industry is investing in coming up with improved processing that includes moulding of the plastics through conventional E-glass and mid-level performance resins. The thermoset and thermoplastic automobiles account for 50% composite market. The relatively low cost of fibre and faster cycle time will ensure easier integration. CFRP can be processed in different methods, including desizing and etching in the prepreg conditions. Open mold approach can be used to prepare the composite samples before the application of fibre and resins on the material. The designer can then fix the carbon fibres in a unidirectional arrangement so that to keep parallel fibres in a state of tension (Mallick, 2007). The processing of prepreg composites is undertaken in consideration of the required volumes. It is among the impediments to the widespread adoption of composites in the automobile industry especially where mass production is needed. The cost of the raw material and lack of suitable manufacturing processes impedes on the use of that material in the production of automobiles. The production engineers are left with the responsibility of making a choice in relation to the required rate of production, if they are going to use CFRP. An average truck within a manufacturing plant will require up to 20,000 units per year, which makes their handling another task. For small cars, the figure is even higher in the ranges of 500,000 units. In addition, CFRP in prepreg conditions are subject to the other conditions, such as scrap production, cycle time and tooling costs that many automobile producers might not be willing to meet (McWilliams, 2007).
The tools used in the composite production are cheaper when compared to those used in metal forming due to single moulding in CFRP. On the other hand, metals require five to six different tools in single component line. However, such simple saving in tool costs can only be realised at low production volumes in CFRP processing but not in higher volumes that require a part of dominance. The processing of CFRP at low volumes can only be maximized in short fibre reinforced thermoplastic injection and also in bulk processing processes (Elmarakbi, 2013). However, it has not been found to be applicable in structural building, not to mention automobile building. The development of long fibre reinforced thermoplastic will bring CFRP closer to a structural fibre. The injection moulding is advantageous as it has short cycle time and produces little scrap. Very few processes are available for medium composite material processing, including the sheet and compression moulding. They have also been automated and used in vehicles with cycle times ranging a span of few minutes (Kelly, 2004).
Question 2
The carbon fibre reinforced polymers have been touted as the answer to the issue of weight and strength in automobile manufacturing. However, in the recent past niche vehicle manufactures have been moving away from CFRP due to the counter elements that make their use of CFRP not only improbable but also costly. The use of CFRP is not so much hinged on automated processes as its competing aluminium material. The low volume production and high priced vehicles mean that using hand-built tools to build them will increase tremendously the cost of production. It will push further the prices of the car. It might not be good for customers of such specialized cars (Society of Automotive Engineers, 2014).
Labour and time considerations are essential factors in the use of CFRP materials in niche vehicle productions as it impacts the production speed. The process also impedes on the advantage of weight-saving potential as soon as high volume construction technique is used. As such, the use of CFRP materials in low volume and niche production of vehicles is rather a factor of the unavailability of the necessary technology and labour than the advantage of the other materials. It implies that a better technology in the future might experience the coming back of composite materials in production of niche vehicles (McWilliams, 2007).
Low volume specialized cars also have special characteristics that cannot be delivered through the use of CFRP material in the production. For instance, the heat-treatment technology that uses aluminium improves the vehicle’s deformability properties and improves its crash absorption, which is something that still appeals to the consumers of such products. Aluminium is also able to deliver similar advantages, such as low weight and better control of inertia, hence better handling by the user among the other benefits.
Reference List
Elmarakbi, A. (2013). Advanced composite materials for automotive applications: structural integrity and crashworthiness. John Wiley & Sons: New York.
Ghassemieh, E. (2012). Materials in automotive application, state of the art and prospects, University of Sheffield, University of Sheffield Press. Available at
Kelly, G. (2004). ‘Joining of carbon fibre reinforced plastics for automobile applications’, Polymer Science and Engineering, 12(5): 19-45.
Mallick, P. (2007). Fiber-reinforced composite materials, manufacturing, and design, Taylor & Francis, New York. Available at
McWilliams, A. (2007). Advanced materials, lightweight materials in transportation report’, Report Code: AVM056A.
Society of Automotive Engineers. (2014) ‘Ferrari prefers aluminum over carbon fiber’, SAE International Ltd. Available at