Automotive Industry Trends
April 2003
Proving its metal: Aluminum boosts vehicle safety
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Safety or fuel efficiency: Do you really need to sacrifice one for the other? “That’s a myth in the auto industry,” notes Dr. Richard Klimisch, vice president of the Aluminum Association (AA). But aluminum vehicle components have proven that time-worn myth to be wrong. Below is a brief look at how aluminum auto components deliver significant safety benefits.
Room to crunch
A pound of aluminum can be as much as two and a half times stronger than a pound of typical automotive steel. But because aluminum is less dense than steel, 0.14 pounds per cubic inch versus steel’s 0.28 pounds, aluminum can be used to make cars bigger and safer, not heavier and less responsive.
In fact, if you design two vehicles of the same weight, the aluminum vehicle can be 20 percent larger than its steel counterpart. Greater size means more crush space and lower G forces slamming into the occupants of the aluminum vehicle.
What’s more, aluminum allows engineers to design more predictable buckling of the vehicle materials, thereby delivering more predictable and stable absorption of crash energy. “Steel folds differently depending on the speed of the accident,” says Klimisch. “That has its advantages, but aluminum can be designed to fold predictably and protect vehicle passengers if a crash occurs.”
Helping SUVs lighten up
Aluminum is currently gaining ground as a way of increasing safety and fuel economy in light trucks and SUVs. “Two major issues with SUV safety are rollovers and vehicle compatibility with smaller cars,” Klimisch explains. “Rollover hazards are fairly obvious. SUVs have a higher center of gravity than sedans because they’re taller, higher off the ground.”
He continues, “With rollover as a risk, roof strength is a concern. But if you strengthen the roof with conventional materials, it will exacerbate the center of gravity problem. Put aluminum high on the vehicle, and the problem is reduced.”
The other issue facing SUV manufacturers is what these vehicular leviathans do to conventional automobiles. “The average SUV is 900 pounds heavier than other cars,” Klimisch states. “That means the passengers in the cars get the worst of the accident. Eighty percent of fatalities occur to the occupants of the cars when the accident involves a car versus an SUV or truck.”
Better handling
Because momentum equals mass times velocity, more mass means more force during an impact. Lightening up larger vehicles with aluminum not only reduces the energy transferred in a crash, it also improves vehicle handling so that drivers have better control and a better chance of avoiding a collision altogether.
“A conventional mid-sized sedan weighing 3,400 pounds, which can accelerate from 0 to 60 in 10.0 seconds, would weigh only 2,600 pounds if made from aluminum, and given the same drivetrain, could accelerate from 0 to 60 in 8.2 seconds,” notes a technical white* paper available from the Aluminum Association. “The light weight of aluminum intensive vehicles also improves braking capability, another important factor in crash avoidance.”
“When you reduce the weight of a vehicle, you go from a car that’s heavy and clunky to one that’s light and responsive,” Klimisch says. “All the super-cars in the world are aluminum: Ferrari’s, Ford’s GT40, Nissan’s 350Z, the BMW Z8. These cars can accelerate faster, break better and they’re a lot more fun to drive.”
No wonder aluminum use in cars has more than doubled over the last 10 years. The secret is out. Aluminum components are a safe bet. 1
1 To read the Aluminum Association’s technical white paper titled “Crashworthiness and Crash Avoidance,” visit http://www.autoaluminum.org/crash.htm.