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From Small Things: Big Differences

Ford Motor Company is aggressively pursuing the small - nano-scale improvements - in its quest to make better, lighter vehicles.

So, how competitive and demanding are things in the auto industry? One way to discern this is to talk with Matthew Zaluzec who is with Ford Research and Advanced Engineering. He's the manager of the Materials Science & Nanotechnology Department. Zaluzec says that given the prevailing conditions, where vehicle manufacturers are looking at the ways and means to provide better quality products without adding to the cost (ideally, no doubt, actually reducing the cost), at Ford they are working at the atomic level. That's right: They are working out the ways and means to improve their products atom-by-atom. Which seems somewhat bizarre, given that Ford has a commitment to reduce vehicle weight on the order of 250 lb. to 750 lb. between 2012 and 2020 (without compromising safety, which would otherwise be a little like throwing the baby out with the bathwater). Think about it: they're talking about taking out a quarter of a ton and they're working with things in the scale of atomic weight: the atomic weight of aluminum, for example, is 26.9815 grams per mole, and we won't pretend that we know what that means, except that it is awfully, well, light.

One of the projects they've undertaken is known as "Atoms to Engines." That's as in conventional internal combustion engines. "We've been making cast aluminum block engines for the better part of 25 or 30 years, and most people think that the material properties are fully optimized," Zaluzec says. Which is a reasonable assumption. After that long a time, they've undoubtedly gotten awfully good at producing aluminum blocks. But then they really started looking at what was what. "When you do a first-principles study of any material system down to the nano size"-and nanometer is one billionth of a meter; if you're reading this in the printed version of the publication, know that this sheet of paper, according to the National Nanotechnology Initiative (www.nano.gov), is about 100,000 nanometers thick-"you can really optimize the performance of a material, like aluminum, magnesium or plastic."

 

Atomic aluminum.

Zaluzec explains that the "Atoms to Engines" project involved looking at the structure, process and properties of aluminum at the atomic level. Through the use of computational materials engineering, they analyzed the constituents of the aluminum used for blocks-the aluminum, silicon, magnesium, etc.-and at the phases involved during the process. While they are now able to perform what they call "Virtual Aluminum Casting," Zaluzec acknowledges that there was a whole lot of "good, old-fashion Edisonian testing" used to develop the models.

Part of the work was questioning assumptions. Apparently, there is a general rule of thumb about, say, the level of impurities that is acceptable in an alloy. "We asked how long ago that question was asked," Zaluzec says, explaining that they started with the "given," and then worked to see what would happen if, say, they changed the level, to model the results. "Most of the casting industry said that it would never work, that it is getting to a level of detail that is a statistical anomaly of a cast alloy. Untrue. But if people want to continue to believe that, that's great." Because they've determined that the control of the microalloy through the make up of the material, as well as the heat treatment and solidification and the like let them achieve an initial performance improvement of 10% out of the aluminum alloy. Which means that they can reduce the weight of the block, which gets back to the goal of significantly reducing the weight of the vehicle. This modeling is now part of the mainstream development for engines at Ford. They used it for the Duratec 3.5-liter V6 engine used in the Ford Edge, as well as the 2.3-liter I-4 that is used to power the Fusion, Milan, and Mazda6. 

 

Not entirely new.

"Nano" is often thought of in the context of a new or significantly different material. "We are not attempting to build an entire new material nanoparticle by nanoparticle," Zaluzec says, explaining that while that may make sense in the electronics or pharmaceutical industries, when you're in the business of making things that weigh some 3,000 lb. or more, that's not a particularly effective approach. But they are trying to achieve significant differences in the bulk materials that they are working with, be it paint or plastics, by adding nanomaterials or, as in the case of Atoms to Engines, controlling the microstructures of a material. "Across all commodities-paint, plastic, light metals-it is really about weight savings." And this weight savings is a consequence of strengthening the materials.

 

Incredible clay.

Consider a polypropylene material, the polymer used for a variety of nonstructural applications including underbody aero-shields and various interior parts from air vents to cupholders. Often, glass fibers are added to increase the strength of the plastic. There may be as much as 30% glass fiber filler. This results in better strength and stiffness. Better mechanical properties. But, Zaluzec says, through the use of nanofillers, there can be significant advantages. That is, the strength of a polymer material is a result of cross linking of the polymer chains. When a glass fiber is introduced into the polymer material, the chains, which are but a small fraction of the size of the glass fiber, wrap onto the fiber. But when a nano clay is introduced, the particle size is such that it is able to fit between polymer chains, which results in increased strength. A consequence of this is that it may be possible to add just 10% fill of a nanoclay in place of the 30% glass. This translates into a lighter component that has physical properties equal to or better than that which it replaces.

So the question is which production Ford vehicles are using nanoclay-strengthened polymers. And the answer, at the moment, is none. Zaluzec explains that there has been a significant amount of work done by industry and academia on creating nano-sized particles. But while that is certainly important, it is only part of the challenge. He explains that the physics of nanoparticles are such that they tend to stick together. "A micron-sized clump of nano particles doesn't do me any good." (A micron, incidentally, is one-millionth of a meter.) Consequently, they are working on "infrastructure" issues, as in developing techniques that will cause the nanoparticles not to clump so that they can be incorporated in plastics and paints and have the characteristics that they were developed to address.

Looking back at what has been accomplished so far, Zaluzec says, "When we were doing some of the aluminum work, there may have been some skepticism. But when the first cost savings hit the books, people said, ‘Wow! This is real." And from all indications, nanotechnology is going to become even more real at Ford as they pursue weight savings through advanced materials.

 

Light & Strong (But Not Sweet)

A honeycomb structure provides a combination of light weight, due to the amount of air between the cells, and strength, due to the configuration of the walls of the cells. Nature is clever.

This type of structure is essentially the means by which CellTechMetals (www.celltechmetals.com; San Diego) is able to produce metal sandwiches (not wax) that are significantly lighter than solid sheets yet provide comparable bending stiffness.

According to Dr. Dirk Mohr of CNRS and École Polytechnique, an 0.84-mm metallic sandwich structure is 45% lighter than a comparable solid sheet, and a 2.78-mm sandwich is 68% lighter than the solid. Another advantage of the honeycombesque material is improved energy absorption in crash situations. According to Mohr, he and his academic colleagues have determined that energy absorption is 70% higher for the sandwich compared to the comparable solid. In a three-point bending test they’ve determined the energy absorption to be 120% higher.

Mohr says that a sandwich could be constructed of two 0.2-mm sheets, one for the top and one for the bottom and two additional sheets that are press formed such that they each have a dimpled surface. These sheets are bonded to the outer sheets and aligned such that the dimples are aligned, then brazed. This center section of the sandwich would measure, say, 1.2-mm. Admittedly, this is not a hexagonal form like an actual honeycomb, but the effect is similar.

CellTech has developed a variety of commercially available steel sheets that have a cellular structure. Doug Cox, company president and CEO, says that these materials, although borne of aerospace applications, have direct applicability to automotive structures, as they can be spot welded and even formed without having to make significant changes to existing processing equipment.

As the drive continues to reduce overall vehicle mass, engineers can take a lesson from the bees.

 

Beyond the Tube

While carbon nanotubes have gained considerable attention due to the fact that they are small, light, and strong, Angstron Materials (www.angstronmaterials.com; Dayton, OH) has developed the next big—or that might be small—thing: nano-graphene platelets (NGPs). These carbon-based particles are on the order of 0.34- to 100-nanometers thick and from 0.5 to 20 microns in width/length. Consequently, there is a high aspect ratio of each particle. These NGPs have high Young’s modulus, high thermal conductivity (five times that of copper), electrical conductivity similar to copper, and are said to be 50 times stronger than steel.

Automotive applications are said to include in polymer composites for items like mirror housings, interior parts, bumpers, and fenders; tires; electrodes for batteries and supercapacitors; and bipolar plates for fuel cells.

 

Slowly Advancing

The subject of this is “advanced materials.” One might think that “advanced” might mean “up-to-date,” “timely,” or even “cutting-edge.” But in the auto industry, when choices can have implications that can have seven-figure consequences, there tends to be a bit of a delay between development and implementation. Which is certainly the case as regards the advanced materials technology available from EXATEC (www.exatec.de; Wixom, MI), a subsidiary of SABIC Innovative Plastics (www.sabic-ip.com). That is, EXATEC has been in business for 10 years, working to move more vehicle manufacturers in the direction of using Lexan polycarbonate (PC) for glazing (a.k.a., window) applications. John Madej, president and CEO of EXATEC, seems confident that there will be some positive movements for the deployment of PC for the simple reason that replacing traditional glass can result in significant weight savings for vehicle manufacturers while providing consumers with appealing features.

That is, there seems to be a trend toward panoramic roofs—sunroofs that have gone supernova. Now one of the consequences of a panoramic roof is that the weight above the beltline is doubled compared with the sheet metal that is ordinarily up top. When looked at from a more holistic point of view, there is even more weight involved, as it is necessary to beef-up other components, such as the suspension, in order to accommodate the additional weight. And the addition of weight means the reduction of fuel efficiency. Madej points out that using PC glazing reduces the weight by 40% to 60%. So clearly there is a benefit.

Of course, as glass has been around approximately forever in the auto industry, there is a certain reticence when it comes to replacing something that is tried-and-true. There are changes afoot, however. Madej says that in the 2004-05 period, EXATEC produced 70 prototype windows to meet industry requests. In the 2006-07 period, that number was up to 430. He says that the vehicle manufacturers are not looking so much at replacement of current glazing, but new applications.

EXATEC has expanded its capabilities in Wixom so that it now has an upgraded wet coating lab, a new 2,300-metric ton Engel injection molding machine, and a full-scale continuous plasma system that applies a protective layer of approximately 2 to 3 microns in thickness to the surface of the PC that makes the material more resistant to scratching. (Essentially, a panel has a series of layers, with the Lexan in the middle and layers for weathering and abrasion on either side.) According to Madej, not only does this allow the production of prototypes, but it could actually serve as a production operation for PC glazed components should a vehicle manufacturer require it.

Presently, there are more than 100 patents related to molding, coating, printing (e.g., applying fractal antennas to the glazing), and defrosting that EXATEC has published or in-process. So it is evident that they’re fairly confident in the technological capabilities—even though it is still an “advanced” material.