Automotive lightweighting trend here to stay
By Don Rosato

Note: This is the first of a four-part series to include automotive lightweighting material advances, process technologies and applications.

Automotive lightweighting goals are driven by several current factors, namely:

What is the important driver in automotive lightweighting?
  • 1. Reduced vehicle fuel consumption
  • 2. Meeting the 54.5 mpg 2025 U.S. CAFE (Corporate Average Fuel Economy) standard
  • 3. Spiraling car weight increases caused by continual addition of car features
  • 4. Reduced greenhouse gas emissions
  1. Changes in government fuel economy and emissions regulations — Reducing structural weight is one of the most important ways of reducing fuel consumption. A 10 percent reduction in vehicle mass yields approximately a 6-8 percent increase in fuel economy;
  2. Rising/fluctuating fuel prices — West Texas Intermediate (WTI) crude was $93.26 on Jan. 15 in New York, down from $98.69 one year ago. After averaging $94 in 2012, the WTI price is expected to average $90 per barrel in 2013 before increasing to an average of $91 per barrel in 2014;
  3. Ever-growing global warming concerns;
  4. Electric, other fuel systems development — Every pound of vehicle weight saved conserves batteries and fuel, providing greater overall energy efficiency and operating range;
  5. Spiraling car weight increases caused by continual addition of car features.
According to the authoritative BCC report “Lightweight Materials in Transportation,” the global market value for lightweight materials used in the transportation industry will reach nearly $153 billion in 2017, up from an estimated $106 billion in 2011, for a five-year compound annual growth rate of 7.5 percent. Transportation OEMs and suppliers want to achieve vehicle lightweighting goals without loss of performance or aesthetics.

Material selection is impacted by assembly methods, formability, paint technologies and corrosion protection requirements, as well as general acceptance by OEMs of performance correlations for alternate materials. Weight-reducing material selection is also impacted by material availability in quantities required for series volume production, cost per unit of weight saved, and material weight saving potential per vehicle produced. The drive for lightweighting results in materials technology increasingly being considered as part of the initial design.

Lightweight automotive alternative material trends

Researchers from MIT and GM have developed a tool for estimating secondary mass savings potential early in the vehicle design process. Using the tool early in the process — before subsystems become locked in — maximizes mass savings. Secondary mass savings are mass reductions that may be achieved in load-bearing vehicle parts when the gross vehicle mass (GVM) is reduced. Mass decompounding is the process by which further reductions are identified via secondary mass savings that result in further reduction of GVM. Maximizing secondary mass savings (SMS) is a key tool for maximizing vehicle fuel economy but can be difficult to achieve given the current design process.

Vehicle weight reduction can be achieved by a combination of (1) material substitution, (2) optimization of component design/system layout, and (3) innovation in manufacturing processes. 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. Material substitution replacing heavier iron and steel with weight-saving advanced composites and other 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 as well as secondary weight reductions in load bearing structures.

International Council on Clean Transportation
Historical fleet CO2 emissions performance — current and future planned standards
Note: NEDC — New European Driving Cycle test standard, LDV — light-duty vehicle

Faced with growing concerns about the impact that automobiles have on the environment, OEMs are embracing the use of lighter weight materials in automotive components and parts, part optimization/consolidation and the use of innovative processes. As a result, plastics and their composites as well as lighter weight metals are increasingly being used to reduce vehicle weight.

Dr. Donald V. “Don” Rosato serves as president of PlastiSource, Inc., a prototype manufacturing, technology development and marketing advisory firm located in Concord, Mass., and is the author of the Vol 1 & 2 "Plastics Technology Handbook."