University Visvesvaraya College of Engineering (2009-10)
A seminar on: Applications of Composite materials in the Automobile industry
Presented by: Praveengouda Patil (Advanced material technology)
Contents Introduction to Composite materials History of composites in the Automobile industry Why Composites? Effect of reduction in weight on the Cost of manufacture and fuel efficiency of the vehicle Effect of using composite structures on safety and crashworthiness Advantages of composites in Styling and part consolidation Effect of using composites in aerodynamic design Scope of composites in the modern auto industry Examples of composites used in the modern Auto industry Problems need to overcome to build a complete composite car Future of composites Bibliography
What is a Composite? A composite material is a homogenous mixture created by the synthetic assembly of two materials of which one is a reinforcing material called fiber and the other is the binding material called matrix. In the modern world composites are used in all the fields like Automotive, Aerospace, Construction industry, Entertainment industry etc.
Characteristics of composite materials They are rigid, with high strength to weight ratio. Good Electrical resistance Resistance to chemicals and weather is high. They have good stiffness (related to automobile skin to limit buckling). Good corrosion resistance. Classification of composites Composites are classified based on the matrix used and reinforcing material used in the formation of the composite material. Based on Matrix used:
Based on the Reinforcing material used
The use of Composites in the Automobile industry is not a new invention, they are used In the automobiles as early as 1930s. History of Composites in the Automobile industry
In 1930- Henry Ford attempted to use Soya oil to produce a Phenolic resin and thence to produce a Wood filled composite material for car bodies (Figure 1).
Henry Ford and his composite car
1940 - flax - a flax reinforced Spitfire fuselage was made at Duxford, Cambridgeshire.
In the 1950s when glass fiber reinforcement material and cold setting polyester resins became commercially available, this put the manufacture of compound curved streamlined automotive bodies into the reach of low volume, low capital companies. The first use of composites by a high volume manufacturer was probably the 1954
1954 Singer Hunter - GRP bonnet and side valences (Source: The North American Singer Owners Club)
By the beginning of the 1960s the low volume car producers were producing structural monologues in hand laid GRP – examples are the Lotus Elite, and these craft level wet hand layup methods were the mainstay of composite production throughout the nineteen sixties, limiting their application to low volume high value specialist sports car manufacture - example the Reliant Scimitar.
The Reliant Scimitar (GTE SE6a shown here) had a hand laid body supported by a steel chassis (Source: Nick Tucker)
In the late 1980s the Pontiac Fiero (Figure 5) laid a good claim as the first mass production Composite intensive car body. The Fiero had a space frame chassis and a body using a number of different types of Composites. The high performance (and cost) image of composites has lead to amusing spin offs such as the manufacture of polypropylene moldings for the juvenile market that look ‘just like carbon fiber’. These articles are of course limited to non-structural applications such as air ducts and trim pieces.
The Pontiac Fiero – mass production composite intensive body (Source: www.pontiacfiero.com)
In the late 1990s, Rover Group (moving later into the BMW Group phase) was working very closely with researchers at the Warwick Manufacturing Group at the University of Warwick. The collaboration (first known as EPIC – Engineering Polymers Integrated Capability), and then SALVO – Structurally Advanced Lightweight Vehicle Objective) had the aim of providing information on new materials, manufacturing technologies, and facilitating the integration of such materials and technologies into volume automotive manufacturing in the new millennium.
Why Composites? To improve fuel efficiency by reducing mass of the vehicle. To Improve safety and crashworthiness To enhance styling and part consolidation. To provide aerodynamic design.
Now we will consider the advantage of composites with regard to the above 4 points:
1) Effect of reduction in weight (by using composites) on the cost of manufacturing and Fuel Efficiency of the vehicle. The reduction in weight of the vehicle by 1Kg on the cost of manufacturing in various industries like Automobile, aeronautical and Space are as follows: Automobile – 5-7 $ /KG Aeronautical –500- 700 $ / KG Space – 5000 to 7000$ /KG. A typical example of BMW Company that used CFC (1.8mm gage) roof design instead of Aluminium (1.2mm gage) This resulted in a weight saving of 1.1 kg per roof valuing 5.5 – 7.0 USD per roof. This finally amounted to a saving of 21,000 USD / year (3000 cars/year platform.)
The table below shows the values of fuel consumption and fuel efficiency for different design types and vehicle weights.
As per this study, a vehicle structure and closures made of normal materials like steel or Aluminum would way 500 KG and will consume 10ltr of fuel per 100 km of distance travelled. If the same structure is made using a HSS (High strength steel) it will weigh 350 KG (30% weight reduction) in this case the vehicle will consume 9.58 ltr per 100 km distance which means 4.2% increase in fuel efficiency. In the third case a Carbon fiber composite is used to build the structure, which weighs 270KG (42% weight reduction) and the vehicle will consume 9.31 ltr per 100 km of distance driven. This means 7% of increase in fuel efficiency. It should be noted that if the same carbon fiber composite structure is used on a car powered by the Diesel engine the fuel efficiency can be increased by a whopping 30% and its 35% with a Full hybrid petrol engine and 45 % in case of a Hybrid Diesel engine.
2) Composites to improve Safety and Crashworthiness.
The crashworthiness design fundamentals include the below points:
Maintain occupant survivable volume or occupant space.
Restrain occupants (within that space)
Limit occupants deceleration within tolerable levels
Retain “ safety- cage “integrity
Minimize post crash hazards
Specific energy of Absorption -- material is said to have good crashworthiness or safe if it has high absorption of energy resulting out of crash. The graph below shows Ideal crush load v/s Crush length of a structure subjected to crash test.
The specific energy of absorption is given by
S.E.A = W / V ρ Where W --- Total Energy absorption = Area under curve V --- Volume of crushed material ρ --- Density of the material The energy is absorbed by the structure by plastic buckling as shown below. As a result the impact of the crash will be reduced at the other end of the structure.
The below graph compares the SEA for metals and composites. The SEA value for Aluminum is around 25KJ/kg and for steel it’s around 35Kj/Kg. And SEA values for the Glass /Epoxy is in the 75 KJ/kg and for Carbon / PEEK it’s as high as 200KJ/kg.This proves that a structure built with a composite is 6 to 8 times safer than a structure built with metals.
The effect of using Composites on safety is listed as follows: Reduces damage and injury to the passenger from accidents. Composite C –fiber composites are preferable over steel/ magnesium or aluminium as they exhibit higher energy absorption values. These structure members are in the form of tubular beams and can be made from glass fiber and carbon fiber for more critical components.
3) Styling and Part consolidation The use of composites (PMCs) in the styling of the interiors of a vehicle has resulted in enhancing the aesthetic look and also in consolidating the parts to fit into small available space inside the vehicle. Some of the examples are shown below:
CFRP Inner deck lid for FORD GT Here the consolidation of 4 parts into one is possible due to ability to create complex curvatures.
LGF PP for POLO front end carrier The use of LGF PP has resulted in Weight saving, parts consolidation, and reduced packaging space and more design freedom.
SMC (Sheet moulding compound) for GM/ FORD pickup truck (truck boxtail gate) The use of SMCs in GM / FORD pickup trucks has resulted in multiple parts consolidation, light weight construction and corrosion resistance.
Glass / Epoxy top sleeper
The use of glass/epoxy top sleeper resulted in light weight, part consolidation and class A surface
4) Effect of using composites on Aerodynamic design Since the composite materials can be easily formed into any shapes they find their use in aerodynamic design of the body of the automobile to reduce air drag. The table below shows the energy losses due to various resistances to the movement of the vehicle.
The Aerodynamic drag increased from 18% in the city driving to 51 % on highways when the vehicle cruises at high speeds. Hence if we can reduce this air drag the fuel efficiency can be improved. The Average drag coefficient (Cd) of modern sedans is around 0.32 achieving Cd of 0.272 would enhance fuel economy (projected) 0.6 mpg in urban driving (2.8 %) 2.8 mpg in highway driving (8.6%) 1.1 mpg in combined fuel economy (4.7%) Studies show that every 2% increase in Cd is expected to enhance fuel economy by 1.4 mpg (.6 %).
Scope of composites in the Modern Auto Industry The automotive companies in the today’s modern world are forced to look for new ways and innovations in manufacturing a car/truck due to fierce competition. The cars today should have all the comforts needed by the customer at low cost. This has led to the use of composite materials in the construction of the body, interiors, chassis, hoods, electrical components etc. The composite materials have the desired properties to suit the requirements. Hence there is more scope for the composites today and also will be in future in the Automobile industry. The below Pie chart shows the amount of composite material used by the Automobile companies during the year 2007. The major players in the automotive world like General Motors (33%) Ford (25%) and Daimler Chrysler (21%) are using the composite materials extensively.
The Pie chart below shows the use of composites in an automobile. About 72% of the composites used will be for Class –A exteriors, and 18% will be used for Structure , under the hood and power train Constitutes about 7% and 3% will be used for interiors.
Examples of Composites in the Automotive Industry There are already a number of composites used in the automotive industry. A few examples Of which follow. These are mainly from a European standpoint although examples of the US industries where some composites are widely used are also included.
Composite Modular Front Ends The first composite front end was introduced in 1987 on a Peugeot 405, manufactured From sheet moulding compound (SMC). Others, e.g., Peugeot 605 and Citroen XM in figure.
Citroën XM – a composite front end (Source: Citroen)
Also a further development has been the Ford Focus (Figure), which has a polymer Composite/steel hybrid front end.
DMC (Dough Moulding Compound mouldings) for Electrical parts Example mouldings include electrical connectors, e.g., fuse box housings, and relay bases, under bonnet covers and manifolds (Figure next page) where higher temperatures are experienced.
Headlamp reflectors are injection moulded in DMC, a resin rich surface on the reflector gives a ‘class A’ finish onto which a metallic coating can be deposited (fig)
Ford Inlet manifold
Use of SMC (Sheet Moulding Compound): Components tend to be large single piece mouldings. Examples include electrical switch boxes, railway carriage panels, domestic external meter boxes (gas and electricity). In the automotive industry, European manufacturers Renault and Citroen produce SMC body panels, tailgates and bonnets (Figure next page). Other popular automotive applications include sun-roof assemblies, rear bumper beams for sports utility vehicles (SUV), truck cab panels and spoilers.
Figure: Citroen Xantia tailgate, produced by Menzolit Fibron
Under bonnet applications include valve covers (Figure) and an SMC cam box. Where stiffness at elevated temperature is needed and extra sound deadening is provided.
Figure Rover engine valve cover moulded by Sertec-PMC
A cam cover (Figure) has been made which takes full advantage of the properties of SMC. A stiff, creep resistant moulding was made to very tight tolerances. The component also has the advantage of damping the gearbox vibrations and withstanding the harsh Seawater environment
Figure: A Rolls Royce cam box (Source: WMG)
The Budd Company has produced a SMC front end moulding for the Ford Taurus in one piece with all fixing inserts included (Figure).
SMC front end moulding for the Ford Taurus (Source: The Budd Company) Another high profile moulding they produced was the windscreen surround for the Plymouth Prowler sports car (Figure) the moulding is both stiffer and lighter than the equivalent steel component, saving around 35% in weight.
Figure: Two-piece SMC windscreen surrounds replaces a multi-part steel pressing (Source: The Budd Company)
Parts manufactured by the Pultrusion process. Chevrolet have reduced the weight of the tailgate for their pickup truck by using a
Pultrusion (Figure. The Pultrusion also has the advantage of being cheaper to produce than the equivalent steel component for the volumes required.
Figure: Chevrolet pickup tailgate by Creative Pultrusion
Drive-shafts and axles can be produced with 60% weight savings using Pultrusion. Spicer and Strong well have produced a single piece drive shaft for a GM pickup truck (Figure 6.23). The Pultrusion has a combination of carbon and glass fibers in vinyl ester resin and is bonded to aluminium end caps. The design is simplified to a single component with excellent corrosion resistance and additional vibration damping.
Use of Glass Mat Thermoplastic (GMT) to produce bumpers Uses for GMT are very varied, from purely aesthetic parts such as cam covers to semi structural parts like load floors, and safety-critical parts such as bumper beams.
Figure: GMT bumper
(Source: Neil Reynolds)
Problems need to be overcome to build a Composite car:
If these problems are tackled efficiently, then we can imagine a car which will be built 100% by the Composites materials.
The Future of Composites In most cases polymer matrix composites (PMC) are in competition against existing metal components. In the case of automotive applications this means steel and aluminium. The advantages of steel are cost, strength, and a route for recycling that is an integral part of the manufacturing process, 50% of manufactured steel finds its way back to the steel works as scrap [1]. The disadvantages are the very high cost of plant and tooling and the limits of ductility. The case for aluminium is also constrained by the relatively high material cost. However, this is usually off-set by an additional weight saving potential. The ductility implication of metals means that complex shapes must be made as Fabrications. Making a similar component from PMC is characterized by cheap plant, but expensive materials, which allow complex shapes to be made as single articles. Whilst PMC are usually accepted for low volume applications, they can only overcome their perceived disadvantages for large scale manufacture by being used to make a more sophisticated product. Composite use on our current vehicles looks set to increase substantially (market trends Suggest up to 10% growth per year in automotive markets) and the use of such components will give the OEM a customer benefit that will be hard to ignore. The successful exploitation of composite materials may well give motor manufacturers the edge they require to stay ahead of the marketplace and it is up to each OEM to ensure they remain at the forefront of this technology.
Summary Composite materials are already being used in various forms throughout the automotive Industry, from sheet moulding compound (SMC) fenders to thermoplastic composite tail doors. The use of composites has been driven by the requirement to save weight and also By the reduction in investment costs associated with composites. Future economic and Environmental pressures will tend to increase the use of low-density materials and Composites in particular.
Bibliography 1) Trends in Automotive thermostat composite use – by automotive composite alliance. 2) Freelance writers Mike and Pam Brady report from the 6th Annual Society of Plastics Engineers (SPE) 3) Vision of CFCs in Automotive field – by Kalyan Sehanobish DOW chemical company. 4) An introduction to automotive composites by Nick Tucker and Kevin Lindsey.
