Lightweighting - Material Productivity Improvement Method

Dec 2018

Lightweighting as method and technology is mature enough now to make a significant impact on manufacturing of cars and air planes and thus help the planet also in promoting less resource consumption. It is a material productivity improvement method.

Gregory E. Peterson is a  principal materials engineer for the Michigan Manufacturing Technology Center, a consulting organization that helps manufactur­ers improve profits and performance.

The MMTC and Peterson were asked in 2017 to find a lighter alternative to the C2’s steel frame for  and produced a composite frame comprising ultra high-strength steel, aluminum, magnesium and carbon fiber. It weighs 33% (or 89 lb.) less. The frame is also 450% stronger. Thus , the Michigan Manufacturing Technol­ogy Center helped develop an aftermarket Corvette (C2) frame that is lighter and stronger than the original.

The amount of fiberglass in the Corvette has given way to more complex, even lighter composite materials. The Formula One engineers create vehicles that can rocket to 62 mph in about 1.7 seconds and weigh less than 2 tons. They’re so good at lightweighting they have a minimum weight of 1,618 lb.

A thumb rule of  lightweighting is that a 10% weight reduction leads to a 6% to 7% increase in fuel economy.

There are more ways to make cars lighter nowadays. The parts are changing in shape and composition, blending various metals and carbon fiber reinforced plastic, relying on next-gen design software and techniques such as additive manufacturing.

If the structure becomes lighter, other elements do as well, from the suspension to the brakes to the tires.

Apart from speed, more and more the drive is for better fuel economy, or more recently increased range on an electric vehicle. The need to reduce your carbon footprint because governments around the world are demanding it is also promoting lightweighting projects.

Now for various reasons, lightweighting has become a top priority of carmakers. 

Lightweighting could potentially reduce vehicle mass by half and boost fuel efficiency by 35%. That’s dramatic; it will take a lot of work.

Innovations in metallurgy, material science and 3D-printing are leading the acceleration.

Aluminum provides a 40% to 45% mass improvement over steel. In 2015, Ford began making its bestselling F-150 pickup truck body out of aluminum, lightening it by 700 lb.

  LIFT (Lightweight Innovations for Tomorrow) Consortium is a public-private partnership of universities, manufacturers and the U.S. Navy’s Office of Naval Research. 

There is  the problem of  cost in  implementing light weight  materials. Traditional carbon steel is currently priced around $0.40/lb., and aluminum more than doubles carbon steel’s price at $0.88.

LIFT, part of the Manufacturing USA network, exists to find the right lightweight materials and way to implement them in the subsequent manufacturing processes. Their statement is that you want to get in the range of about $2 incremental cost for every pound saved. Otherwise, it’s really not a good value for the customer. 

Aluminum sheet now falls within this range, as does the third generation of advanced high-strength steel. AHSS  can reduce weight by 25%-39% over conventional steel. Aluminum has less mass than AHSS, but is weaker and is more expensive. Aluminum is lighter than Advanced High-Strength Steel, but costs more. AHSS seems to have the edge in emissions when comparing well-to-wheel scores. A life cycle assessment model by the WSA found that AHSS reduced at best 6,600 lb. of CO², while aluminum was 3,300. But recycling of aluminum is one-tenth of the energy of getting it out of ground and there’s a lot available. This may give preference to aluminum.

Magnesium is an up-and-coming metal. It costs $2.10/lb. but can reach up to 60% in weight savings.

The real solution from LIFT’s perspective will be found when the perfect combination of these metals (and plastics and carbon fiber) are implemented. In each scenario they first tinker with the array of prospective materials to create optimal strength, safety and fuel economy. Then they have to ensure the different metals don’t negatively interact

The Corvette frame developed by MMTC, which will be commercialized by a low-volume manufacturer in Michigan, used continuous bonds with structural adhesives, while being 450% stiffer in bending, is easier to manufacture, and requires inexpensive tooling and minimal labor.

High (Carbon) Fiber 

“Carbon fiber has the best potential for lightweighting, but takes a lot of energy.

Carbon fiber is 55% lighter than carbon steel and can be ten times stronger, but the limiting factor is cost. Despite the price, which could be up to $500/lb., aerospace manufacturers value the performance and use it. Half of the Airbus A350 XWB airliner’s total weight is carbon fiber reinforced plastic. Formula One, where expense always comes in a distant second to performance, also relies heavily on the material.

A new low-cost carbon fiber is available at $5/lb. Engineers are now figuring out how to attain the high throughput the auto industry needs. A Boeing or Airbus can take several hours to create one part. The goal is to reach 90 seconds to make a carbon fiber lift gate or hood.

The cycle time is limiting CFRP at BMW. The i3 and i8 hybrid sports cars had been made out of CFRP and could get up to 76 mpg. But for the new iNext cars are produced in Din­golfing, Germany, where the cycle times are 60 seconds, BMW has to  revert back to a metal frame. 

The carbon fiber industry will be worth about $6.1 billion in 2023, more than double the 2017 value, according to a markting research estimate. 

The education of people involved in the manufacturing has to be in using fibres. With composites, you’re concerned with how the fibers are aligned, the thermoset system like epoxy, temperature, and the time exposed to that temperature to achieve the properties you want.

A New Design Method 

Climate change is real. A driving force behind GM’s is the vision of a future with zero crashes, zero emissions and zero congestion.

Why does a seat belt bracket look the way it does? Because of machining requirements. But what if machining was re­placed by additive manufacturing?

A revolutionary new approach GM starts with is Autodesk’s generative design software, an engineering software tool that uses artificial intelligence and cloud computing to manifest dozens to hundreds of possible models based on physical requirements. For a bracket, it must attach at certain lengths and support specific loads, AI eliminates material that was sub-optimized only for the manufacturing process.

Generative design opens up a whole new set of lightweighting opportunities. 

The end result that GM achieved is a stainless-steel bracket that looks more like a human knee, smoother with ligament-like supports, as opposed to a robust, square shape comprised of eight welded pieces. The new version is also 40% lighter and 20% stronger.

General Motors - Generative Design
uploaded by Autodesk ___________________


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https://www.industryweek.com/technology-and-iiot/road-lightweighting-tech-materials-leading-way

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