A Lighter Future with Thermoplastic Solutions

By on September 26, 2016 in DESIGN LINES, MATERIAL MATTERS

Answering the need of manufacturers for lightweight solutions, thermoplastic-based materials provide an array of properties that make them attractive, including low density, high strength and rigidity, and tailored thermal expansion properties with recyclability.

By Scott Fallon and Umamaheswaran Venkatakrishnan (UV), SABIC

Introduction

The automotive industry must address several challenges over the next decade. A top priority is overcoming the design hurdles that will allow vehicle manufacturers to achieve the increasingly stringent emissions and fuel-efficiency targets set by regulatory bodies across the world. While targets differ by region and the complexity of emission credits and calculations of fleet efficiency can be a challenge, the simple fact remains that vehicle manufacturers must strive to close the gap between today’s performance and tomorrow’s targets.

The automotive industry is employing various strategies: improved and alternative drivetrain solutions, enhanced aerodynamics, reduced rolling resistance and reduced vehicle weight. Measures to achieve the latter are evident in practically every car model launched today. This trend will continue, particularly with the pressure to offset weight gains from adding components to satisfy consumer demand for new features, such as adaptive safety, infotainment and connectivity systems.

Even with the introduction of electrified powertrains, the industry still needs solutions to counterbalance the increase in weight that comes with the addition of new systems and components like batteries and others enabling electrification. Every kilogram (kg) of weight saved extends range and performance. In addition, weight-out will remain important to reduce system costs and enhance driving performance. Even smaller-sized cars with their tight physical dimensions require lightweight solutions.

The material industries—plastics and composites, steel, aluminum and magnesium—are working to respond to the vehicle manufacturers’ need for lightweight solutions. No one material will serve as a panacea. However, one material class, in particular, continues to trend upward and presents major weight-reduction opportunities across each application segment. That would be plastics and composites, especially thermoplastic-based materials, which provide an array of properties that make them attractive for manufacturing (low density, high strength and rigidity, and tailored thermal expansion properties and recyclability). Speaking to the lightweighting value of plastics, today, these materials make up about 50 percent of a car’s volume, yet account for less than 10 percent of a car’s total weight.

One can expect broader adoption of thermoplastic materials in applications where they are proven and greater penetration in other applications as they are validated. Given the different requirements of individual parts and systems, one must take an application-specific view when considering opportunities to take advantage of the many benefits provided by these materials. Looking at the adoption of thermoplastics today and expected developments within the next decade demonstrates how the use of these thermoplastic materials may emerge over time.

Proven Solutions

Today, a wide number of opportunities across all vehicle segments are available to take advantage of thermoplastics as a strong, lightweight choice.

A good example lies in the chassis area in which engineering thermoplastics are replacing multiple metal-based crash and energy-management solutions in front and rear bumpers. A thermoplastic rear-bumper beam can save up to 2 kilograms of weight, while also providing excellent energy absorption and increasing the flexibility of the part compared to steel. Thermoplastic energy-absorber solutions can help vehicle manufacturers design to, and comply with, Global Technical Requirements (GTRs) for pedestrian-safety bumper systems.

Ford introduced its first production energy absorber (EA) for pedestrian protection molded from a thermoplastic resin on its 2009 Kuga crossover. The automaker’s 2014 Fusion Mondeo was launched with a single-piece front bumper EA with tuning flexibility to meet the competing requirements that exist in the global market. Made from a

Photo 1 inset

Long glass fiber-reinforced polypropylene (LGFPP), a composite resin, is in demand today to replace metal in several structural applications like front-end modules (FEMs), door modules, inner tailgate components and instrument panels. As much as 50 percent in weight savings is possible with this polypropylene-based material, which offers the high stiffness and dimensional stability for the production of quality parts.

The difference made by a plastic composite material like this is evident when comparing its use in an FEM carrier versus one with a polyamide-steel hybrid (PA hybrid). According to data verified by GreenOrder, a leading sustainability consulting firm, an FEM molded out of this composite material has a life-cycle greenhouse gas (GHG) footprint of 78 kg versus 149 kg with a PA/steel hybrid solution, a 48-percent reduction. That data also shows that the FEM with LGFPP resin also has a lower life-cycle energy footprint of 1,200 megajoule (MJ) versus 2,140 MJ for one with a PA/steel hybrid solution, a 44-percent reduction. Scaling this data up to 200,000 FEMs with LGFPP resin versus a PA/steel hybrid solution, a manufacturer could avoid emitting as much GHG as driving 1,000 cars 100,000 kilometers.

Read the rest of this article in the upcoming edition of Lightweighting World magazine, available in early October.

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