In powertrain engineering, plastics applications for the powertrain help automakers reduce weight and integrate parts, which boosts performance and delivers productivity and cost savings. Today, plastics penetration is as high as 20 kilograms per car, depending on engine size and region. And there are still more opportunities for plastics use.
The Benefits of Engineering Plastics
Engineering plastics and new high-performance composite materials can offer:
Plastics Reduce Weight to Improve Fuel Economy
Engineering plastics, such as nylon, have the best weight factor compared to metals. The density of steel more than offsets its potential for low wall thickness. Aluminum and magnesium also cannot overcome their density disadvantage.
Several studies show a 25-kilogram weight reduction can yield a 1% increase in fuel economy. And that’s before talking about cost.
Plastics Lower Tooling Costs
A typical injection-molded part in nylon will show a tool life of over one million units, while die-cast aluminum and magnesium have a much shorter tool life of about 70,000 to 100,000 shots. Nylon also offers more design and tooling flexibility compared to metals, making it a great solution in powertrain engineering.
Aluminum and magnesium parts are on average 20%–40% less able to deliver productivity and cost savings compared to nylon. Only when a steel part run is well over a million units does steel see any advantage. However, steel is limited in design and tooling flexibility, not to mention weight.
Plastics in Air Duct Systems
Machined prototypes of nylon air intake manifolds began in the mid-1980s. By moving from lost core technology to two- or more-piece vibration-welded designs, GM and Porsche led the way for high-volume adoptions, particularly with Ford Mustang V8.
To meet higher temperature requirements, high EGR (exhaust-gas recirculation) rates, and modular design approaches, high-temperature aromatic polyimides, known as PPAs, are being used. PPAs can handle temperatures greater than 200°C, be used for EGR inlets and can integrate more parts. For example, VW‘s design uses PPAs to combine the charge-air cooler into the manifold.
Air duct systems are moving away from heavier aluminum and costly stainless and galvanized steel to flexible, blow-moldable plastics such as nylon 66 and PPA. In the process, clamps, brackets and silicone boots can be eliminated, and plastics assembly is easier than metal.
The key is engineering the material, whether it is DuPont™ Hytrel® thermoplastic elastomer with operation temperatures from -30°C to 150°C, or high-temperature nylon 66, to offer both rigid and flexible sections in one shot.
Our Global Blow Molding Technical Center in Geneva produces 3-D suction pipes and co-extruded pipes. We use a test rig to verify part performance. “Hot-side” air ducts are under development in our high-temperature nylon HSLX resin with temperature resistance up to 210°C.
Plastics in the Transmission
With the increase of gear speeds from 4 to 6 or even 8, plastics can help reduce transmission size and weight.
The TEMIC electronic transmission control that houses the solenoids is best suited for dimensionally stable and highly reinforced PPAs.
GM is using flexible Hytrel® elastomer to both seal and serve as a baffle for transmission fluid aeration to improve performance and allow the fluid to be filled once for the car’s lifetime.
Other parts include DuPont™ Vespel® polyimide seal rings and nylon transmission oil pans.
High-Resistance Oil Pans
DuPont materials for powertrain engineering reduce vehicle weight by replacing heavier metal or die-cast products. Our materials combine high impact resistance over a wide temperature range with high resistance to lubricants, road salts and other media present in vehicles.
An example of our CAE (computer-aided engineering) contributions is our work on an oil pan for Buss and Daimler. For this oil pan, our mold-flow technique allowed parts to be molded without stresses, keeping the strength needed in the right areas of the part. And we correlated actual impact analysis with our dynamic CAE structural analysis tools. These tools were critical for part performance and will become even more valuable as we work together to further integrate functions in oil handling systems.
We’ve learned how to extend the limits of glass-reinforced nylon for better flow, which is important for complex shapes such as an engine cover part. The material’s spiral flow length is 20%–30% better than a conventional 35% glass-reinforced nylon 66.
If the need is for stiffness, look at the tensile modulus numbers for long glass compositions. At the high end of our offering, a 50% long glass PPA, such as our HTN 51LG50, used for a prototype suspension bracket, offers a tensile modulus of 18,000 MPa with little, if any, loss in toughness.
At DuPont, we offer more than materials formulation. OEMs and component and systems suppliers want to understand how well materials will perform over time.
Using our design and manufacturing process development tools, we can predict part performance over the life of the vehicle. We use these tools in our three regional development centers to model, analyze, optimize and communicate with OEMs and suppliers from concept to commercial launch. Globally, we operate on a 24/7 basis to help provide solutions to complex problems.
Together with various OEM R&D groups we’re taking these tools and our physical test equipment further into the realm of predictive engineering to look at crashworthiness, performance over time with heat and chemical exposure, and more.
Molding analysis is integrated into structural analysis to improve accuracy in predicting static and time-dependent loads. We use NVH analysis tools to predict and tune part responses to transmitted vibration and air and coolant flow.
Plastics for Powertrain Engineering Offer Endless Possibilities
Air intake manifolds, air ducts, suction pipes, oil pans, engine front covers, exhaust gas recirculation cooler units in PPA, turbocharger housings in hybrid plastic including PPA, and even plastic mufflers in PPA and nylon are just some of the myriad opportunities for weight and cost savings under the hood.
Materials price and performance are a tradeoff. Often, a higher-value material can bring down the cost of a part or system if used in a better way. For example, a PPA with better heat aging than a conventional nylon can allow for thinner walls and a lower end cost.
Our track record is good, with more than one-third of our product offerings launching since 2006. We’re working on a new nylon offering with better heat aging and chemical resistance, and we continue to make progress in advanced thermoplastic composites.
Together with OEMs and suppliers we continue to find new uses for our plastics and composite materials and new ways to tool them, while advancing our process tools to test and predict performance.