With increasingly stringent CO2 emission reduction targets imposed by the European Union, manufacturers must keep pace. The first possible solution is the electrification of the automotive fleet. The second is the reduction of the weight of combustion vehicles to lower their emissions. Substituting metal parts with plastic or composite parts could lead to substantial weight savings. In terms of their properties, these materials reach the same level of performance as metals, but then why are our vehicles still mainly made of metal? ALCIMED, a consulting company specializing in innovation and the development of new markets, provides an overview of the use of plastic materials in the automotive industry and the obstacles to their widespread use.
The European Union has set a target for car manufacturers in Europe of a maximum of 95 grams of CO2 emitted per kilometer travelled by 2021 (average value valid for a vehicle of 1390 kilograms, the average weight of new vehicles put on the market). Additionally, in mid-December 2018, the European Parliament and Council reached a consensus on a new target to reduce average CO2 emissions by 15% by 2025 and by 37.5% by 2030 compared to the results achieved in 2021. However, the situation remains very disparate between manufacturers, as highlighted in the latest report of the ICCT (International Council on Clean Transportation). While Toyota is the manufacturer closest to its target for 2021 (with a further 9 grams reduction still to be achieved), others still have significant work ahead of them. Manufacturers such as Fiat, Chrysler, Hyundai, Ford, Volkswagen or Daimler, remain more than 25 grams away from their targets for 2021, which seems increasingly difficult to achieve.
A roadmap for reducing CO2 emissions
Electrification of the automotive fleet remains a solution, but the low penetration rate of electric vehicles will not allow manufacturers to reach their 2030 target. In fact, it is expected that 75% of the cars sold that same year will still be petrol or diesel vehicles. However, manufacturers have several levers to achieve the objective of reduced emissions. The most effective way would be to concentrate on the engines, for example by reducing the displacement. However, several experts agree that a performance plateau would be reached. The second lever is reducing vehicle weight, for which the substitution of metal parts with plastics seems to be a promising solution.
Vehicles made of more and more plastics
The plastics market in the automotive sector was estimated at approximately €25 billion in 2016 for 10 million tons. Its growth by 2025 is expected to be about 10% per year. This evolution is not only driven by the increase in vehicle sales, estimated at 2% annually; it is also the result of the integration of plastics in many applications previously reserved for metal.
Still today, 80% of the weight of vehicles is made up of metal parts. Some experts estimate that the use of plastics for the vehicle structure would allow substantial weight savings, up to more than 200 kilograms corresponding to a reduction in CO2 emissions of about 12 grams.
For the time being, 50% of the plastic used in vehicles is used for bodywork components. These are mainly PP (polypropylene) bonnets, tailgates, bumpers, fenders… The second major use of plastic materials is in vehicle interiors (40%), particularly in dashboards or door interiors. They are mainly made from PP, PU (polyurethane) or ABS (acrylonitrile butadiene styrene). Finally, specialty plastics, such as PPS (polyphenylene sulfide), PEEK (polyetheretherketone) or PA (polyamide), are also used for applications in the engine environment. This is because specific properties (chemical, thermal, etc.) are required for ventilation systems, fuel distribution systems or tanks. The latter are a perfect example of parts whose composition has completely switched from metal to plastic.
PSA has recently integrated composite materials into its EMP2 modular platform for around fifteen vehicles in its range. A new rear floor made of glass-fiber reinforced thermoset flooring was developed with Plastic Omnium for the 308. For all the structural or semi-structural parts, the plastic materials used are reinforced with glass, carbon or natural fibers. These fibers are required to obtain sufficient physical properties, particularly in stress failure, to pass crash tests.
Major obstacles for democratization and rapid transition
Despite mechanical properties that match the performance levels of metallic materials, composite materials are slow to gain widespread acceptance in this sector. The identified obstacles are mainly the cost but also safety and recycling:
- – High production costs. The manufacturing facilities of the automotive industry are designed for the production of metal parts and the investment required to change production lines would be massive. And the investment required to change production lines would be massive. In addition, the production rates of the automotive industry are quite high, and it would be impossible to keep them up with composite materials. It will be important to take the opportunity of a change of modular platform to make the required investments and promote the integration of composite materials into vehicles.
- – High material costs. The automotive industry must keep its costs low. Steel or aluminum costs between 1 and 3 €/kg while carbon fibers cost about 15€/kg. Currently, there are projects such as FORCE II (IRT Jules Verne) to reduce the cost of these fibers to below €8/kg.
- – Uncertainty as to the predictability of behavior during crashes. While the behavior of steel under stress is perfectly known and therefore predictable, that of composite materials is less reproducible. It is more difficult for manufacturers to predict the behavior of these materials during crashes and to ensure passenger safety.
- – Complexity of the recycling process. Current regulations require that 85% of the materials in each vehicle be recyclable. Steel is highly recycled, which is not the case for composite materials.
What are the levers?
The democratization of plastics, and specifically composite materials, in the automotive sector will inevitably be linked to the development of new types of materials that are cheaper or are produced using simpler manufacturing processes, particularly those that allow high production rates.
Producers have adopted different strategies to reduce costs. Some are focusing on the design of the parts or the ease of their integration. One example is the Peugeot 308 floor, which used to be made up of 30 metal parts, but has now been reduced to only 4 parts, made only of plastic. This modification made it possible to reduce the number of manipulations on the lines and thus reduce the final cost. In addition, a metal frame has been added to the part to facilitate its integration into the vehicle.
Even if a complete replacement of metal by plastic is not for the foreseeable future, some manufacturers have nevertheless started this revolution. For example, the start-up Gazelle Tech or BMW offer vehicles with a cockpit made entirely of composite materials.
“Some manufacturers have an ambitious strategy like BMW with its i3. This is a turning point and an example for other manufacturers who are closely observing the evolution of these materials over time. However, the price of this vehicle is still too high to talk about democratization.” concludes Jakub Rams, Manager of the Energy, Environment & Mobility team at Alcimed.