“Advanced high-strength steel is the fastest growing material on a vehicle,” said Hall. “We are actually replacing ourselves – mild steel and high-strength, low-alloy steel – with high-strength steel so we can reduce the mass of a vehicle.”

She called steel the “first choice” for automakers, but acknowledged that other materials are gaining ground. “Steel is the most cost-effective, and [automakers’] infrastructure is set up for steel, so they try to use it first to hit performance targets and mass reduction,” said Hall. “But if they can’t do it with steel, they’ll work with other materials.” Materials like CFRP.

A Look at Aluminum

Henry Bertolini, technical director at Pennex Aluminum Co., began his presentation at ADM by admitting one of the challenges for aluminum: “How do we improve our strength and not go up in cost?” he asked. That’s a concern shared by CFRP suppliers and one that hinders both aluminum and composites from gaining more market share in the automotive sector.

chevy-colorado-steel

More than 72 percent of the cab structure of the 2015 Chevrolet Colorado comprises advanced HSS, according to Jody Hall, vice president of the automotive market for the Steel Development Institute. The center pillar is made with one piece of press hardened Martensitic steel that’s thinner on the top and bottom than in the middle to optimize performance. “They don’t need as much mass in the top and bottom, so there’s less material there,” says Hall. “And in today’s market, every gram counts.” Photo Credit: General Motors

“Only 2 percent of a vehicle’s mass is aluminum structure,” said Bertolini. “The low-hanging fruit has been harvested. Taking simple parts and converting them to aluminum has been done for quite a while. Now the hard part has to be done: We have to design for aluminum.”

Bertolini cites the Cadillac CT6, which debuted in 2016, as an example. The body of the mixed-material luxury sedan is 64 percent aluminum and weighs approximately 200 pounds less than a similar size vehicle using predominantly steel. The structure also uses less parts. For example, the front-door hinge pillars feature 13 high-pressure aluminum die castings, each one replacing 35 steel stampings, according to Motor Trends magazine.

The aluminum industry hopes to gain traction with customers by touting its benefits: short production lead times, low tooling costs, recyclability and the ease with which it can be fabricated into integral shapes. But aluminum faces significant hurdles, many of which will sound familiar to composites professionals. The first is convincing automakers to design for aluminum, rather than simply replace steel components.