Realities and perspectives: Use of light materials in the automotive industry

Use of light materials in the automotive industry

Motto:

In the industry which made the horse theft drop significantly, any Ford customer used to be able to pick the colour of their cars as long as it was black.

Competitiveness is growing stronger in the current market, where “the final validation for the manufactured automotive vehicles is granted”. This situation triggers a continuous increase in demands regarding the quality, cost and performance of the automotive vehicles. In response, the offer is comprehensive, as well as varied, to cover a wider range of tastes and options of potential customers. To that end, specialists’ concerns are focused on turning into account the latest findings of science and technique. A significant role in the matter is that of using light materials for the parts of the automotive vehicles. This is also necessary to meet the saving fuel demands and, implicitly, to reduce the level of CO2 emissions from the biggest urban polluter.

A concern that stood over time in this area is that of replacing cast iron and steel with Aluminium (Al) and its alloys. This trend is followed by the gradual replacement of the latter with plastic materials and composites. This way, a significant evolution has been achieved in the construction of automotive vehicles with the introduction of plastic materials, first only as replacements of traditional materials (leather, natural textile materials, metallic springs). With the appearance of the ABS, polyurethane, polycarbonates, polyacetate, fluorocarbon, acrylic resins etc., they have become basic elements for parts with decorative and functional role. Evolution in the area has continued with daring solutions that have finally led to the appearance of materials with brand new properties obtained by combining resins with highly resistant synthetic fibres and metallic sheets.

One of these plastic materials, the polycarbonate, is used more and more by automotive vehicles manufacturers. By 3D shaping and casting of multi-components, the designers have the freedom to create innovative and varied shapes. The roof weight of automotive vehicles is reduced by up to 50% in the case of polycarbonate compared to glass. Not only fuel consumption is reduced, but the stability of the automotive vehicle is also increased by lowering the centre of gravity. Another advantage of using plastic materials such as polycarbonate, is impact resistance. This means that, in case of accident, the roof will not break or crack. Roofs, as well as other automotive components, such as sun visors, can be manufactured using polycarbonate.

The polyurethane composite material (PU) is light and durable as well. The central element of the material is made of paper honeycombs covered by a mixture of polyurethane and reinforcing fibres. Due to its high stability, the composite material is ideal for case parts of up to 2 square metres. For example, the frame of a retractable hard-top weighs up to 25% less than steel, can be cast and 3D-shaped, provides good acoustics and has excellent thermal insulation properties.

Another solution for reducing the weight of automotive vehicles is to use the “Webasto Glas Protect R”. This technology permits an ultra-resistant thin cover to be applied to the interior surface of the protection window. If the window breaks, the adherent cover keeps all the glass fragments together. The window remains in one piece and passengers don’t get in contact with broken glass pieces. The “Webasto Glas Protect R” is a lot lighter than the traditionally used laminated protection glass, because the cover permits thinner glass panels to be used. Thus, it is possible to build much lighter roof tops.

To get a picture on the evolution of tendencies in the structure of the materials used in the automotive building industry, we recall that in 1988, the share of the materials used in a vehicle manufactured by General Motors was: cast iron 10.5%, steel 60%, Al 6.7%, Pb 0.7%, Cu 1.0%, Zn 0.3%, glass 2.7%, rubber 2.8%, plastic materials 9.0%, others 6.3%. For future models, the large manufacturing companies extend the range of non-conventional materials. Thus, if the weight of light alloy and plastic material parts is 8 – 10% for the European medium-class automotive vehicles in production (Volkswagen and Audi 100) and 16% for the Japanese cars (Datsun), it is expected to reach 20 -35% over the next years.

For example, Renault, for its EVE experimental model, uses light alloy and plastic material parts that weigh 35% of the total car mass. Porsche 928 has 70 Al parts in construction, weighing 265 kg which is 29% of total car mass. Peugeot, for its experimental prototype VERA, uses 165 kg of parts made of plastic and composite materials. Fiat has included in the design of the VSS plastic material parts representing 25% of the total car mass. By comparing the mechanical results and densities of different materials, it results that one 1kg Al part can replace a 2.2kg cast iron part. If we add the 0.5% kg saving obtained through the dependent effects (lightness of engine, transmission, suspension etc.), for 1 kg of Al, used in the construction of an automotive vehicle, it results a 1.7kg weight reduction.

The representative parts that can be made of plastic and composite materials are: doors, engine and trunk hoods, pavilion floors, sun visors, grids, ornaments, wheels, panel and board panel accessories, consoles, seats, interior stuffing, driving shafts (70% of aramid fibres and 30% of epoxide resins), back and lateral windows (made of Lusitia SAR-Super Abrasive abrasion-resistant polish), rear axles (65% glass fibres and 35% SMC-Sheet Moulding Compound), fender lamps and turn signals, flexible electric circuits, cans and electric accumulator separators, tanks, wires of supply and breaking circuits, ventilators, gliding and rolling bearings, radiator basins, components of the steering system, air filters, fuels and lubricants, gears, engine rockers, arches, torsion beams, drive shaft etc. (fig. 1).

Plastic and composite materials are also used in the construction of engines. Thus, the HOLTZBERG engine (made in the US), with 4 cylinders and 234kw power, has 60% of its parts (admission tank, piston rockers, clack parts, lids, pistons) made of special TORLON materials, a polymer that is very resistant to traction. The 234 model engine of the Polimotor Research (SUA), already put into series production, with a 130kw power at 5800 rpm has its block and cylinder head made of plastic materials.

New constructive concepts have been explored including steel only as support for the polymer-made body case panels, driving elements, wheels and binnacle.

Regarding body case innovations, it is interesting to observe that Hyunday Motors has conceived the “Intrado FCEV” model (presented at the Geneva Motor Show in 2014). Its weight has been reduced due to its carbon fibre-made body case reinforced with plastic materials. Thus, the series manufacturing of automotive vehicles exclusively made of plastic materials is currently a vision underway.

We are witnessing the “fourth industrial revolution” characterised by the fusion of technologies and erasure of clear limits between the physical, biological and digital spheres. The new innovation wave, that of interconnected objects, bio robotics or nanotechnology and nanomaterials, has already accessed the production of super-materials designed for the automotive industry.  Materials and systems with predefined properties and behaviour are created based on knowledge and services for an entire range of applications, while minimising any potential negative impact on environment and health. Thus, the structure of the new types of components that accesses the automotive vehicle manufacturing industry at full speed is shaped.

We will only mention some of the many wonder materials with super-qualities that wait to become internationally renowned:

  • Microlattice – the lightest metal known, lighter than the Styrofoam, but as tough as the titanium, manufactured by Boeing specialists;
  • Graphene – a million times thinner than a sheet of paper, tougher than steel, transparent, synthetized by Manchester University Laboratory;
  • Self-healing plastic – water pipes cracks will close by themselves and satellites can repair their own faults etc., a discovery of Illinois University researchers;
  • Carbon nanotubes – 300 times more resistant than superior steel, high quality alloy.

The 3Rs – Recovery, Recycling, Reuse

One cannot analyse the use of plastic materials in everyday life, including in the automotive vehicle industry, without implementing NOW with full responsibility the concept of the 3 Rs – Recovery, Recycling, Reuse. Thus, we can put an end to the waste of resources and pollution. It is more than obvious that the application of the 3 Rs is vital for the health of the Planet. According to INCDTP-Bucharest-Romania data, a 15% share of the plastic materials used worldwide to obtain technical products is used in the automotive industry, which is quite significant. As the largest economy of the world, the US, only recovers 4% of plastic material waste, specialists estimate that the planetary ocean contains 5.23 trillion tonnes of plastic material. At the Davos International Forum of January 2016, the programmatic document said that “if the current trend is maintained, in 2050, the world’s seas and oceans, will contain more plastic than fish”, meaning that waste will suffocate the future of a day-by-day resource-impoverished planet!

(Featured image: The Ford Motor Company – ford.com)

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