While recent developments in advanced materials, such as carbon fiber reinforced polymer composites, seem to have grabbed all the news headlines lately, more and more industrial manufacturers are taking another look at the next-generation of steel and aluminum alloys to produce stronger, lighter, and safer products that can be easily recycled. We take a look.
Thoughts at Orgatec on Manufacturing with Sustainable Materials
During Formaspace Office’s recent visit to the Orgatec contract furniture show in Cologne, Germany, we were fascinated by the environmentally-friendly furniture created by the Dutch manufacturer VEPA. The company is using recycled plastic — including discarded plastic bottles made of PET plastic dredge up from the bottom of Amsterdam’s famous canals — to create a line of fashionable office seating and conference tables.
Finding ways to recycle plastic waste is good news at a time when the amount of plastic materials (especially micro-plastics) that have found their way into our oceans is threatening to contaminate the food chain that we depend on.
But capturing and recycling post-consumer plastic waste is just one part of the solution. Reducing plastic waste during the manufacturing process itself is just as important.
Take BMW’s sustainable manufacturing processes for example. To reduce weight and improve the driving range of their i3 series electric vehicles, BMW engineers created a unique body structure made of carbon fiber reinforced plastic (CFRP).
The raw carbon fiber material (which comes from a US-based factory in Moses Lake, WA) is woven into carbon fiber fabric mats at a BMW factory in Bavaria. Later, during the body panel forming process, the fiber mats are wetted with plastic and pressed into shape, using a die press, then cured to create the vehicle’s structural components.
Unfortunately, because the carbon mats are rectangular (but the parts are not), there is a significant amount of spoilage when the unused material is trimmed away. Fortunately, BMW engineers found a way to use these leftover scrap carbon mat pieces by piecing them together to create new exterior skins for the roof of the i3 — an area of the car where the mismatched grain edges are far less noticeable to the consumer.
Reducing carbon fiber material waste during the manufacturing process is good news. However, the outlook is less clear once the product has reached the end of its useful life. While BMW designed the vehicle to be dissembled for recycling, it’s a slow, cumbersome process to cut the individual CFRP pieces apart for recovery and reprocessing.
And worse, the recycled carbon fiber material isn’t nearly as strong as the original first-generation material because the recovery process often results in cutting the long strands of carbon fiber into shorter segments, reducing its strength.
That got us thinking about the inherent advantages of manufacturing products out of aluminum and steel, both of which have a long, successful track record in recycling programs. We thought it would be a good idea to take a look at what metallurgists working in the aluminum and steel industry have been up to. As it turns out, they’ve been busy developing new alloys that are giving carbon fiber composite materials a run for the money, with the added advantage that these metals can be easily recycled again and again.
Aluminum-Lithium Alloys Give Composite Aircraft a Run for the Money
Aluminum has long been the material of choice for passenger aircraft, thanks to its combination of light weight and high strength. Indeed, up until the introduction of the carbon fiber-bodied Boeing 787, commercial aircraft manufacturers generally limited their use of composite materials to smaller components, such as flight control surfaces, radomes, fairing panels, and so forth.
The 787 led many analysts to predict that the future of passenger aircraft belonged to carbon fiber-based design, and Airbus did indeed follow Boeing’s lead by introducing their own A-350 passenger jet, which uses carbon fiber fuselage exterior panels (in contrast to Boeing’s 787, which is built from a series of full circumference carbon fiber “barrels” tied together with titanium fasteners).
But when the aerospace engineers at Quebec-based Bombardier were evaluating material choices for their own clean-sheet, narrow-bodied jet, they took a hard look at carbon fiber. In the end, they elected to use a new type of aluminum-lithium alloy for the fuselage of their new narrow-body CSeries passenger jets.
(Pardon the interruption to the metallurgy discussion but we have to take a moment to explain a few things about the development of this aircraft. Boeing’s reaction to the new Bombardier CSeries was to take legal action, claiming that they were offering the jets to Delta Airlines at prices far below market value; Boeing also claimed the company benefited from illegal government subsidies. After being hit with a US tariff of 300%, Bombardier saw no other viable economic option other than selling a majority stake in the project to Airbus, which rechristened the plane as their Airbus A220 series. In a further twist, Airbus intends to build the A220 aircraft at their final assembly plant in Mobile, Alabama, in an effort to avoid most of the US tariff penalties. We now return to the topic at hand.)
The choice of Aluminum-Lithium (Al-Li) in aerospace applications offers several advantages over traditional aluminum.
Most importantly, Lithium is both the lightest solid and the lightest metal on the periodic table, so adding it reduces overall weight quite significantly. (Adding 1% Lithium reduces weight by 3%.) How is this possible? At the atomic level, lithium atoms replace the aluminum atoms located at the each of corners of the individual crystal structures that make up the alloy material. As a result, Bombardier/Airbus engineers claim their aircraft is 8 tons lighter than a Boeing 737 MAX 7 series. Of course, the 737 is larger, but this is still an impressive statistic.
Compared to traditional aluminum materials, Al-Li also appears to offer increased stiffness, better corrosion resistance, improved fatigue strength, as well as improved resistance to crack propagation. As a result, Airbus engineers expect that the new Al-Li fuselages can remain in service for a full 12 years before requiring a major overhaul (compared to 6 years for conventional aluminum structures).
Ai-Li materials also have a significant advantage over carbon fiber structures. For example, they can be recycled more easily than carbon fiber. (The only major restriction is that Al-Li materials destined for recycling must be segregated and not mixed with traditional aluminum materials.) Also, Al-Li structures are inherently resistant to lightning strikes in flight (unlike carbon-fiber planes which require special internal grounding systems).
Are we likely to see more Al-Li aerospace applications? Yes. Boeing has signaled its intentions to use Al-Li to manufacture the fuselage of its next-generation of its 777 wide-body aircraft, the 777-X.
Metals companies are taking notice of the shift as well. Alcoa (now renamed Arconic Inc) has built its own Li-Ai production facility in Elkhart, Indiana to compete with Constellium (formerly Alcan) who currently holds the contract to produce the Li-Al material (dubbed Airwave) for the Airbus A220.
(To learn more about recent developments in the aircraft industry, see our report New Innovations in Aerospace Technology.)
Ford Shocks Industry by Switching to Aluminum for America’s Best Selling Vehicle
Bombardier and Airbus are not the only major manufacturers who have taken another look at aluminum. For the thirteenth generation of their best-selling Ford F-150 truck, Ford Motor Company made a radical decision that upended years of tradition – they switched from manufacturing truck bodies out of steel to ones made of aluminum.
The top executive at Ford overseeing this decision at the time was Alan Mulally, an ex-Boeing executive with extensive hands-on experience building aluminum aircraft (he was in charge of the hugely successful 777 program). So, there was rampant speculation that Mulally’s experience building aluminum aircraft helped pave the way for the Ford truck program’s decision.
Among those in favor was F-150’s Chief Engineer Peter Reyes. He knew it was time to implement a clean-sheet redesign using aluminum, rather than try to make incremental PMI program changes to try to get more performance out of their existing steel trucks.
Fortunately, they took their time to do the proper research and development. Starting back in 2009, Ford starting building covert F-series trucks prototypes made of aluminum and placed them with customers. (Reyes notes that none of the customers who tested the trucks realized they were in fact aluminum-bodied vehicles.) This allowed Ford design and manufacturing engineers to gain the necessary experience: to select appropriate alloys, material gauge thicknesses, and heat treatments, to develop new stamping machine die designs for aluminum sheets, and to specifying suitable reinforcements, brackets, and fasteners.
The new aluminum-bodied Ford F-150 trucks are about 750 pounds lighter than the previous generations made from steel, which has allowed Ford engineers to not only deliver significantly better fuel economy, but they were able to significantly improve the driving dynamics and increase the towing capacity.
According to Raj Nair, Group VP, Ford Global Product Development, “It was certainly a big decision. As we went through the analysis of where we saw fuel economy going, when we went through the analysis of what customers were looking for, particularly looking for an improvement in capability and performance, we saw an opportunity to really to do a very focused lightweighting of the vehicle. Not just for fuel economy, but to reinvest (that) into capability as well … The payload increases. The towing capability increases. The braking performance, the acceleration, ride, handling, all of it gets better.”
Lining up the supply chain to secure enough aluminum alloy raw material was a significant challenge. Remember, Ford sold 896,764 F-150 trucks in the US in 2017, and it’s been the bestselling vehicle in the US since 1986, so aluminum suppliers needed to be able to ramp up quickly to meet Ford’s huge volume requirements. In fact, Ford believes it gained a first-mover advantage — by “locking up” all the available aluminum supplies with long-term contracts — to such an extent that other vehicle manufacturers would have difficulty sourcing enough raw materials to introduce their own versions of aluminum-bodied vehicles.
Ford also needed to train its dealer network and independent body shops on the proper techniques to repair aluminum body parts damaged in accidents.
Marketing issues were another challenge facing Ford, who needed to convince its large, tradition-oriented customer base that the changeover to aluminum was a positive step. Doug Scott, Ford’s Marketing Manager for the F-150, was all too aware that some of their long-term customers might question whether aluminum was strong enough to meet the product’s brand promise “Built Ford Tough.” For these customers, Scott said they used commonly-understood metaphors, such as strong aluminum tools and toolboxes, to illustrate the point that aluminum was tough enough for the job. They also provided aluminum trucks to mining and construction companies to get testimonials. Finally, they entered an aluminum-bodied F-150 into the Baja race held in Mexico to prove the truck’s strength and durability.
Using Multiple Steel Alloys within Structures to Increase Vehicle Crash Protection
But what about steel?
Steel certainly has a bright future at Formaspace, where we use it to build our industry-famous, extra heavy-duty tables, workstations, desks, and benching systems.
New steel alloys are also finding their way into the latest automotive designs as well, thanks to their high strength to weight ratios.
For example, we turn to Honda’s Acura division where the engineers have been developing a new crash-resistant structural cage concept, known as ACE, to protect occupants during a vehicle crash.
The second generation of the ACE body structure is found in the 2019 Acura RDX SUV (which also happens to be the first Honda/Acura product entirely designed AND manufactured in the USA).
Stephen Frey, the Chief Engineer for the Acura RDX program, explains that the engineers were able to use advanced engineering crash analysis to pinpoint the specific areas where they needed to incorporated high strength steel while keeping the overall vehicle weight down.
The results are impressive. The new RDX design increased the chassis stiffness by 38%, and during crash testing, the RDX received the highest possible safety award from the IIHS: their top safety pick ‘plus.’
Frey explains that “making a (vehicle) body that is rigid is actually an easy engineering solution. Making a car that is stylish is easy to do. Making it stylish, rigid, and have the cargo capacity that a (compact) SUV needs, that’s the magic.”
Thanks to the use of high-strength steel, Acura engineers were able to produce a stronger structure that was 10kg lighter. There were also significant savings on tooling costs as well because they were able to eliminate the gussets and brackets used in previous designs, thanks to the use of higher strength steel.
Frey reports they were also very careful in avoiding waste as well while minimizing weight. “It’s a flat piece of steel; we cut that into 5 different pieces to make the outer ring, then laser weld it together. This allows us to be efficient with the blanking size, but it allows us to weld different thicknesses together. So the outer ring has three different thicknesses of material. We put the thick stuff where we needed it, and the thin stuff where we didn’t. And that’s heated up to 900 C*, and it’s put in a giant press and it’s stamped to the final shape in one stamp… there are cooling passages inside the die itself — it immediately quenches it, which is where it gets that strength.”
* 900C is equivalent to 1,652 F. For those not familiar with metallurgy, a variety of heat treatments (both heating and cooling) can make metal stronger, more resistant to fatigue, etc.
What is Happening in the Materials Research Labs?
The examples from Bombardier/Airbus, Ford Motor Company, and Honda/Acura make the point that there is plenty of life left for using advanced aluminum and steel alloys in manufacturing.
What else can we expect in the coming years?
Well, we certainly expect to see an increased adoption of aluminum and steel alloys in additive manufacturing (AM), which is sometimes referred to as 3D Printing.
An interesting new example is Scalmalloy, a patented aluminum alloy developed by APWORKS that’s specifically designed to be used in additive manufacturing equipment. There are even efforts underway to perfect the challenge of printing out stainless-steel products using additive manufacturing techniques. As a further sign that the additive manufacturing market is maturing, the standards organization ASTM has begun issuing formal standards, such as the forthcoming F3318 standard, which covers additively manufactured parts (AlSi10Mg) produced using a laser powder bed fusion (L-PBF) process.
Meanwhile, material scientists are busy developing a wide range of materials with unique properties, including:
- The world’s most durable material.
- An ultra-high-strength, lightweight magnesium alloy that incorporates 14% silicon carbide nanoparticles.
- New aluminum alloys that are stronger than stainless steel.
- Materials that are completely resistant to liquids.
Indeed, there is increasing talk that the era of “Unobtanium” may be coming to a close.
*Unobtanium is the wistful name for a material that doesn’t yet exist but is needed to solve an engineering problem.
In other words, advances in material science may allow product designers and engineers to create new structures and design concepts that solve real-world problems, leaving it up to the material scientists to use their expertise to create the necessary designer materials needed that fit the design requirements, not the other way around.
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