Aluminum: Toward 50% Body Content

Aluminum BIW and closure parts are the key to achieving both regulatory and OEM goals for improved vehicle efficiency going forward.

May 1, 2019

Lindsay Brooke

Based on the 2017 Aluminum Assoc. summary report, to save 7% vehicle mass by 2028 at least another 170 lb. of gross mass reduction needs to be achieved through material substitution. “3rd-Gen” steels, CFRP, polycarbonate windows, and multi material body structures. (Image credit: DUCKERFRONTIER)

To vehicle-development teams, peaceful coexistence is the 2020’s way of describing the relationship between steel and aluminum. Sure, the two giant materials industries will continue their battle to conquest one another’s market share. But for vehicle planners and program-development teams, the ferrous and light metals are an increasingly effective and popular combination. As experts have noted elsewhere in this issue, the mixed-materials trend is becoming an enduring one, as evidenced across the landscape of recent new-vehicle introductions.

Aluminum crossmembers and sub-frames are engineered harmoniously into light-truck ladder frames whose finely-tailored use of various advanced high-strength steel grades could fill engineering textbooks. Suspension control arms have become the focus of new CAE-driven designs that have brought flip-flop applications within some OEMs — what was once a heavy steel fabrication is changed to a far lighter aluminum casting, then to a forging, only to be transformed again into an even lighter steel stamping full of precisely-located lightening holes. Further iterations in aluminum — or perhaps CFRP composite, or a combination of metal and composite — are likely to follow.

Honda R&D’s Stephen Frey, chief engineer on the 2019 Acura RDX, told Automotive Engineering during an appearance on Autoline TV that high-strength aluminum extrusions and use of aluminum sheet in closures will play an increasingly sympatico role in Honda’s use of new AHSS grades that are being deployed in new body structures for impact-resistance and crash safety. Frey also high-lighted how advanced joining technologies, led by the now-proven rivet-bonding process, have enabled Honda engineers to re-design entire body and chassis sections and thus increase aluminum’s vital role as a mass-reduction agent.

“The emerging pattern has more aluminum added with each model change-over over a 10-15-year period” driven by closures, crash management, steering knuckles and structural vacuum die cast parts,” explained Chris Brower, director of DuckerFrontier (formerly Ducker Worldwide).

He noted that the amount of growth will depend on the concentration of the weight savings on specific vehicle classes. A mass reduction of 20-25% on 20% of the vehicles is much more beneficial for aluminum than 5% mass reduction on all the vehicles, particularly if the fleet mix is more predominately large truck based or SUV platforms. Aluminum content growth also will depend on how much “mass creep” must be offset, and any improvements in the value proposition of other materials relative to aluminum.

Per technology-implementation pathways as cited in U.S. EPA and NHTSA studies, to achieve a 7% mass savings (approx. 270 lb./123 kg) while maintaining vehicle size, with a market concentration on light trucks, “high-growth aluminum components will continue to be a key to the equation,” Brower asserts.

“High-strength steel, magnesium and CFRP are critical,” he said. “Aluminum BIW and closure parts, however, are the key levers to achieving both regulatory and OEM goals for vehicle improvements over the next 10 to 15 years.”