PPT
PPT
PPT
Mechanical 3rd Year Vidya Vikas College of Engineering and Technology tiruchengode
karthiknivechennai@gmail.com
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:
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 ofsuch 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.
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
S.E.A = W / V
Where W --- Total Energy absorption = Area under curve V --- Volume of crushed material --- 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 its around 35Kj/Kg. And SEA values for the Glass /Epoxy is in the 75 KJ/kg and for Carbon / PEEK its 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.
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.
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.
The use of glass/epoxy top sleeper resulted in light weight, part consolidation and class A surface
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 todays 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.
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)
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.
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
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)
Pultrusion (Figure. The Pultrusion also has the advantage of being cheaper to produce than the equivalent steel component for the volumes required.
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 excellentcorrosionresistanceandadditionalvibrationdamping.
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.
If these problems are tackled efficiently, then we can imagine a car which will be built 100% by the Composites materials.
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.