Body in White, Lightweighting and Mixed Materials

Cars are made from the inside-out.  From the frame and structural elements, and the other parts you can’t see, to the point where the sheet metal components are welded together, and what’s recognizable as a car really takes shape.  “Body in white” is that stage before those external elements are painted, before moving parts like doors and hoods, and trim assemblies, like glass and seats, have been made a part of the frame.

(Wikipedia says Body in White, or BIW, “derives from manufacturing practices before steel unibody monocoques.”  Auto bodies were made on a separate chassis to which with the engine, suspension, and fenders were attached. “The manufacturers built or purchased wooden bodies (with thin, non-structural metal sheets on the outside) to bolt onto the frame. The bodies were painted white prior to the final color.”)

Increasingly, light weight, high-performance metals and composite materials–including magnesium, aluminum and carbon fiber–are in all the ground-up applications of auto manufacturing:
door panels, hoods, trunk lids and tailgates, dashboards, and, importantly, wheels.  Example: a recent comprehensive research report, Magnesium Alloy Wheels Market: Production, Sales, Supply,
Demand, Analysis & Forecast to 2021, projects a global growth of that market of CAGR 20.47%.
*a sample of the report is available at


image     img-eco2-3     Aluminum-Rolls

This growing trend of automakers moving to a multi-material vehicle design approach reflects the demand for overall lighter, aerodynamically-superior and more fuel-efficient vehicles in light of the need to reduce dependence on fossil fuels.

Example:  A survey of automakers by research and consulting giant Ducker Worldwide shows an expected growth of total aluminum content in vehicles from 397 pounds per vehicle (PPV) in 2015 to 565 PPV by 2028, a figure representing 16 percent of total vehicle weight.

“That is the highest growth rate of aluminum in automotive applications in the history of the automobile,” Kaiser Aluminum executive Doug Richman said at a recent presentation at the Society of Collision Repair Specialists’ OEM Collision Repair Technology Summit. “It’s unprecedented.” “I can assure you that every single one of the programs my organization is working on is a multi-material body-in-white,” Richman added. “Steel, aluminum and. . .magnesium and composites are being deployed.”

By 2028, some 25% of the North American production fleet will have a multi-material body-in-white, the Ducker survey reports. With the exception of the Ford F-150’s all-aluminum body-in-white, “the multi-material vehicle is the future,” said Mr. Richman.

Abey Abraham, Managing Director, Automotive Materials, at Ducker says, “To further improve fuel economy, battery range, safety and overall driving performance, automakers no longer default to a single material and instead are pursuing a multi-material design approach where the best material is chosen for the best application.

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In the case of wheels, especially forged magnesium wheels, lighter is better.  Wheels account for most of a vehicle’s “unsprung weight.”  (The parts of a car held up by the springs is its sprung weight; the rest is unsprung weight, i.e., tires, wheels, wheel bearings and hubs, brake assemblies).  Magnesium wheels are 25% lighter than comparable aluminum ones.  For professionals and everyday auto drivers and motorcycle enthusiasts, magnesium wheels provide faster acceleration and reduced stopping/braking distance, improved fuel efficiency and fewer CO2 emissions, and an increase in the lifecycles of tires, brake pads, and suspension.  Moreover, they result in a more comfortable, safer ride with more assured cornering and turning.


On a related note for wheelsnews readers, IMA (the International Magnesium Association) announces GALM GLOBAL AUTOMOTIVE LIGHTWEIGHT MATERIALS FOR NEW MODEL ELECTRIC AND HYBRID BODY ENGINEERING, April 24-26, 2018 in Munich, Germany. The GALM( Global Automotive Lightweight Materials) series are the world’s leading conferences on automotive lightweighting.




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