Can plastics compete in the lightweighting marathon?

Continental Structural Plastics’ Frank Macher discusses the race for superiority within the field of lightweighting, tipping plastics as a future front-runner. By Freddie Holmes

Pressure is mounting on OEMs and suppliers to invest heavily in solutions that can raise the bar for fuel efficiency. In addition, events in 2015 such as the diesel emissions scandal and the 2015 Paris Climate Conference (COP21) are weighing heavily on OEMs and suppliers. The automotive sector is being scrutinised more carefully than ever before to make cleaner vehicles.

In the US, the industry is required to meet a fleet average fuel economy of 54.5mpg by 2025, while in Europe, emissions regulations demand new cars achieve a fleet average of 95g CO2/km by 2021 (phased in from 2020). Vehicle lightweighting has cemented itself as a vital component within the vast majority of vehicle manufacturers’ strategies to meet such targets.

While plastics have played a relatively small role in vehicle production for a number of years, Frank Macher, Chairman and Chief Executive of Continental Structural Plastics (CSP), believes that composite materials will soon become integral to lightweighting strategies.

“Plastics had virtually no position in vehicles, but now play a significant role in both interior and exterior applications,” he explains. “In the last two to three years, car companies have frequently found that there are applications where plastic and composite materials can play a significant role in the vehicle going forward.”

Rationale for light vehicles

The 2015 F-150 pick-up truck made headlines when Ford made the switch from a steel-intensive body to an aluminium-intensive design. However, Macher points to potential issues regarding corrosion, maintenance and repair work associated with metal use as a potential driver for plastic-intensive design.

Plastics had virtually no position in vehicles, but now play a significant role in both interior and exterior applications

Pick-up trucks are owned not only by the casual driver, but also the commercial driver who requires a truck for day-to-day work, often in very harsh environments. Aluminium may not be the optimum material in this case, Macher says. “Aluminium is softer and has less dent resistance than steel, so the real challenge will be to see what aluminium-intensive vehicles look like two or three years down the road. Have they withstood maintenance issues, and can aluminium continue to fulfil the role?”

Macher suggests that plastic-intensive design will be the next step after aluminium, and notes that CSP has been developing composite boxes in light-duty trucks since 2001. “You would have to look hard to find any kind of denting, because it really doesn’t dent,” he says. Macher refers to CSP’s Ultra Lite composite material that is 50% glass, providing significant stiffness and impact strength. Composites utilising a high proportion of glass content have evolved to the point where they are competitive with aluminium not only in terms of gross weight reductions, but also provide additional benefits. “In most cases, they’re less expensive, they cost less to tool, you get away from issues of corrosion, and there are better opportunities for dramatic styling on external parts,” explains Macher.

In the future, he is confident that a number of opportunities exist to convert traditional metals to composites. “We’ll just have to wait and see how the market reacts. It’s quite a race for superiority right now,” he observes.

Increasing the payload

While weight savings in the passenger car segment are generally developed for efficiency and emissions purposes, most within the heavy-duty truck industry view weight savings as an opportunity to increase payloads. This means that more goods can be transported per journey, potentially reducing the number of trucks on the road.

What’s more, Macher advises that composite materials can be deployed across the entire body of a truck: “You can see the use of ultra-light materials in liquid carriers, and to a lesser extent, on conventional sleeper cabs. On a vehicle of that type today, we can save weight simply by substituting the current material with our Ultra Lite composite and save almost 300 pounds (136kg) per vehicle.” He believes composites will gain importance within these larger trucks in future as the US Environmental Protection Agency (EPA) begins to raise fuel economy and emissions standards.

In the last two to three years, car companies have frequently found that there are applications where plastic and composite materials can play a significant role in the vehicle going forward

“You’ll see a thrust for increased weight savings in commercial trucks in future,” he affirms, anticipating the North American market to make the initial push. In China, the majority of heavy-duty trucks currently use steel-intensive designs; CSP, says Macher, is in discussions with “key customers” in China to develop composite solutions. “In China, there is an increasing interest in improving aerodynamics, styling, and ultimately fuel economy and emissions because there is a major issue with pollution,” he explains.

A simple swap?

Many manufacturers are recognising the potential benefits that both plastic and composite materials can offer over conventional metals such as steel and aluminium. Along with greater styling flexibility, one of the key value propositions prompting an increased use of composites is that manufacturing a body panel or component is a far simpler process, using fewer production stages and resulting in lower overall costs.

When analysing the business case for switching to a composite material, understanding the cost differential between materials is critical – and complex, explains Macher: “Aluminium is US$2 per pound for sheet metal parts, but you have to work in all of the differences in specific gravity, thickness and structural properties,” he points out. Such cost evaluations include conversion of the aluminium to rolled stock, coating for formability, stamping and tooling – all of which add time and money.

What’s more, a typical aluminium body panel would require six dies, whereas making the same part in plastic would require just a single mould. “You basically make the part, and it’s finished,” he says. “Our Ultra Lite composite material, which is used in the new Chevrolet Corvette, is less expensive than aluminium; there is around a 5% to 10% cost advantage on a high volume application where we need to add tools. On a low volume application, where we only need one set of tools, we may have as much as a 20% saving over aluminium.”

Along with greater styling flexibility, one of the key value propositions prompting an increased use of composites is that manufacturing a body panel or component is a far simpler process, using fewer production stages and resulting in lower overall costs

In many cases, traditional materials can be easily switched to plastic thanks to computer aided design (CAD) and computer aided manufacturing (CAM), which ensure that the resulting plastic component meets requirements.

“The outside surface is the same whether it’s steel, aluminium or plastic,” he points out, “so we can design to meet whatever requirements are necessary – be it structural integrity, noise, vibration and harshness (NVH) or pedestrian protection – and simulate the various road requirements. We can then convert the component or panel to our material and create a substantial saving in weight.”

From plastic, to carbon fibre

Macher expects an increased use of composites to eventually initiate a carbon fibre revolution. The material is currently reserved for luxury, performance and low-volume models that can afford to absorb higher raw material and manufacturing costs. Carbon fibre is often touted as the ultimate material in terms of weight and strength, but is currently out of reach for many. This is primed to change over the next decade, Macher observes.

“Between 2018 and 2020, you will start to see combinations of carbon fibre with glass, and between 2022 and 2025 significant increases in pure carbon fibre where ultra-lightweighting will be essential to meet CAFE standards. The need for weight saving will be so significant that there will be a migration to carbon fibre simply because it provides the best value in terms of strength to weight,” he explains.

No one is really willing at this point to expand carbon fibre use until laws mandate that it is required for improving fuel economy late in 2024 in order to meet those standards

As it stands, carbon fibre is significantly more expensive than aluminium or steel – currently around US$12 per pound (US$26.4/kg), against aluminium’s US$2/lb and steel’s US$0.50/lb. “No one is really willing at this point to expand carbon fibre use until laws mandate that it is required for improving fuel economy late in 2024 in order to meet those standards,” Macher affirms. “OEMs will continue to dabble in carbon fibre, but price will delay the decision to convert to high volume until there are absolutely no other alternatives.”

2025 and beyond should see carbon fibre used extensively in new vehicles, not only in external panels and components, but also in structures such as engine cradles, cross-beams and even body-in-white (BIW) applications.

Overall, it is reasonable to expect a continued transition away from steel to aluminium, before plastics, composites and ultimately carbon fibre become integral to both light- and heavy-duty design going forward.

“The future pipeline is becoming impregnated with a number of different applications that will be firsts for plastic materials,” says Macher, and concludes that one of the primary hurdles holding back structural plastics has been solved: “For applications such as BIW, heat requirements of the paint line need to be met, for composites to be successful. Considerable work has been done and there has been a breakthrough of new materials with that capability. That barrier needed to be broken in order to see an onslaught of new materials in the plastic composites industry.”

This article is part of an exclusive Automotive World report on lightweighting. Follow this link to download a copy of Special report: Vehicle lightweighting

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