Note: This is the first of a three-part article series covering automotive lightweighting (1) trends, (2) material/process advances and (3) applications.

Auto lightweighting goals are driven by changes in government regulations for fuel emissions, ongoing global warming concerns, fluctuating fuel prices, the development of electric vehicles and other fuel systems, and spiraling car weight increases caused by the continual addition of car features.

Key plastic materials, process technologies, and applications to take note of are as follows:

Auto Lightweighting with Alternative Materials

Consumer preferences have limited the downsizing options available to automakers, and safety and performance standards have resulted in a very limited ability to reduce weight further with conventional materials. The lightweighting potential of every vehicle component is under investigation.

Replacing heavier iron and steel with weight-saving advanced composites, plastics, aluminum, magnesium, and advanced high-strength steel is essential for boosting fuel economy. Material substitution is dependent on mechanical properties, cost, design, and manufacturing capabilities.

In addition to reduced fuel consumption, weight reduction enables smaller power plant and energy storage systems, with corresponding cost and/or performance benefits and secondary weight reductions in load-bearing structures.

Center for Automotive Research
Alternative 2025 lightweight material options.

Carbon Fiber-Reinforced Thermoplastic Composites Introduced

Carbon fiber-reinforced thermoplastic composites represent a long stride toward the use of carbon fiber in the mass production of automobiles and other products.

Sereebo, a Teijin technology, cuts compression molding cycle times to less than one minute using thermoplastic carbon fiber compounds. Traditionally, carbon fiber was mixed with thermoset plastic, which required five minutes of molding time, making it primarily suitable only for high-end, specialized applications.

Teijin
Carbon fiber composite performance versus metals

Higher 'Strength/Formability' Micromilled Aluminum

Alcoa's Micromill will enable the manufacturing of the next-generation of automotive aluminum products, and will help capture the growing demand from automakers for lighter-weight, yet durable and formable materials.

The patented process significantly changes the microstructure of the metal, allowing the production of aluminum alloys for automotive applications that have 40 percent greater formability and 30 percent greater strength than the incumbent aluminum while meeting stringent automotive surface quality requirements.

Alcoa
Higher "strength/formability" micromilled aluminum

Polyamide (PA) Gear Shift Module

Polyamide replaces metal and outperforms materials such as PPS (polyphenylene sulfide) or PEEK (polyether ether ketone). LGF (long glass fiber) polyamide, Grivory HT1VL-50X from EMS-Grivory, featuring high stiffness and creep resistance at high temperature is being used to replace metal for an Audi gear shift module, a seven-gear dual clutch transmission produced by FTE Automotive.

Grivory HT1VL-50X is a surface-optimized Grivory HT1 with 50 weight percent special LGF reinforcement. The material is characterized by very high stiffness and strength as well as very good resistance to oils and chemicals.

Grivory HT1 maintains its excellent mechanical properties even at high temperatures. It also provides very good dimensional stability and low tendency to creep. Grivory HT1VL-50X has higher stiffness and strength values, increased energy absorption and notched impact strength, a higher heat deflection temperature and strikingly increased creep resistance.

In addition, the long glass fibers are more evenly oriented in an injection-molded component, which greatly reduces directional dependency of the material properties.

EMS-Grivory
Audi gear shift module (left, Moldflow model; right, plastic part)

The global shift in automotive manufacturing hasn’t slowed plastics innovation and the adoption of new plastic materials. In 2006, Japan passed the U.S. to become the world’s largest car manufacturer. This position changed again when in 2009 when China overtook Japan for the top spot with a 35 percent market share in vehicles produced. U.S. production has gone to 25 percent in the last five years.

Recently, vehicle weight has actually been increasing as OEMs continuously add car features. Reversing this growing weight spiral has become a top priority.

Over the past 15 years, cars have not become lighter, but 30 percent heavier in some cases. The VW Golf, for example, which weighed 800 kilograms at its launch in 1974, now weighs 1,200 kilograms. Thus, material producers, car manufacturers, suppliers, processors, and various institutes and associations have taken up the challenge of reducing automotive vehicle weight.

To meet ambitious new government fuel economy targets, global automakers are considering every avenue of part redesign and consolidation, including a recent renewed interest in automotive under-the-hood metal-to-plastics conversions and further plastics-to-plastics refinements. Engineers are turning to advanced engineered plastics technology to meet new design goals, particularly weight reduction, as a result of:

• Rising long-term and fluctuating short-term fuel prices.
• For example, U.S. automakers must achieve a Corporate Average Fuel Economy (CAFE) of 35 miles per gallon by 2020 and 54.5 mpg by 2025.
• The first step increases CAFE standards for passenger vehicles and light trucks by 4.5 percent per year over the five years spanning 2012 to 2016. This will increase passenger vehicle standards to 35.7 mpg and light trucks to 28.6 mpg. NHTSA estimates that these interim standards will save 55 billion gallons of gasoline and reduce CO₂ emissions by 521 million metric tons.
• Automakers will also be able to earn credits if they exceed CAFE standards, and can either bank them or sell them to other automakers at a cost below what the fine would be for not meeting the standards.
• A 10 percent reduction in vehicle mass yields a 6 percent increase in fuel economy.

New material uses to reduce automotive weight will include:

• Greater use of engineered plastics and composites in car body panels.
• Long and continuous fiber technology for structural parts.
• More use of carbon fiber-reinforced plastic for structural and other parts as lower-cost composites are developed.
• Polycarbonate and acrylic as glazing, including car roofs and rear ends.
• Advanced nylons in under-the-hood applications.
• Foaming and glass bead technology to reduce part density.
• More use of plastic-metal and organic hybrid technology.
• Advances in thin gauge high-performance steel.
• Growing use of aluminum and magnesium metals.