The Car of Tomorrow in 2008 marked the first time NASCAR stock cars used a splitter to provide front downforce. A splitter is simply a shelf that splits the air. Some air goes over the splitter, some goes under. The air that goes on top of the splitter gets slowed down, and thus exerts more pressure than the air going under. That creates a net force down, pushing the front wheels into the ground.
When they were designing the splitter, the big question was what to make it from? They tried an awful lot of materials. The first splitters used during testing were wood. They needed a material that was strong and stiff because you’re talking about over a thousand pounds of force. You also didn’t want something really really heavy out front because that’s going to make it difficult to balance the car.
The first thought would be carbon fiber composite. Carbon fiber composite is an increasingly popular material, being used in NASCAR for the dashboard and seats because it’s strong and light. Carbon fiber composites are used in other racing series for everything from the monocoque (the body) to wheels.
To make carbon fiber composite, you start with long threads of very strong carbon fiber. The threads are woven into sheets of fabric, just like your sheets or any other woven material. Multiple sheets of fabric are laid into a mold and flooded with a resin (a liquid very much like epoxy).
A composite combines two materials, ending up with a material that has properties better than if you just looked at the two materials together. The resin binds together the fabric sheets and the produce is as strong and stiff as steel, but at one fifth the weight.
The negative is that carbon fiber is expensive – about 2o times as much as steel. It takes a long time to make carbon fibers and very high temperatures. High temperatures mean high costs.
The other problem with carbon fiber is that it is extremely brittle. Glass is an example of a brittle material – when it breaks, it shatters into a zillion tiny little pieces. That last thing you want is for forty two cars to run over the pieces of someone’s splitter in an accident.
Milliken & Company is a textile firm that has their research headquarters in Spartanburg, South Carolina. It’s a huge complex and much of the work there is focused on fibers for rugs. Rugs used to be made of wool and cotton, but as we developed fancier polymers, we replaced the natural fibers with synthetic.
Milliken created a material called Tegris, which is a monocomposite. Tegris starts with a fiber, just like carbon fiber composite. Except the fiber has two sections. The inner section of the fiber is nicely ordered polypropylene oxide (a bunch of carbon, hydrogen and oxygen in an order that makes from a pretty strong material. The outside of the fiber is made from the same material, but the atoms are arranged in a slightly messier manner, which makes that part of the fiber have a lower melting temperature.
They make fabric from the polypropylene oxide, just as they do from carbon fiber, but instead of infusing it with resin, they apply high pressure and moderate temperatures. The outside of the fiber melts together, creating a hard, solid material from the fabric. The picture at left is a piece that Milliken gave me in which the top half has been turned into a composite and the bottom is just the fabric.
The lower part, by the way, makes a great cat toy. I know that’s not what it’s designed for, but the cat goes after it like crazy when I’m careless enough to leave it laying around.
Anyway, the resulting material has only 70 percent of the strength of carbon fiber composite; however, it doesn’t break easily. We’ve seen drivers drag splitters through grass and concrete and you really have to work to break the splitter. Not only is the material used in the splitter, there’s a sheet of it in the drivers side door to prevent cockpit intrusions. As the video below shows, it’s pretty good protection.
If you want to see even more picture of things trying and failing to break Tegris, take a look at Milliken’s materials video page.
When a splitter does break, it tends to delaminate, which means it separates back into layers along the planes of the fabric. No splinters or shards for other cars to run over. The two most important aspects are that it’s about ten percent of the cost of carbon fiber and it’s fully recyclable. Recyclability is an issue for advanced materials because a composite isn’t just two things together – it’s two things combined to make them one thing, so breaking them back down again is near impossible.
Of course, a material this versatile has lots and lots of potential. Native Watercraft created a kayak made from Tegris. It’s no longer being produced, but you can find plenty of them on the web for about $1100. This is a twelve foot kayak that weighs 36 lbs – and seven of those pounds are the seat.
They’re also looking at applications in the military for battle armor and even for architectural panels. Even the NFL is getting into the game – Tegris is being used in shoulder pads.
Tumi has dibs on Tegris for travel applications and they’ve got a Tegris-based suitcase on the market, which you have to admit looks pretty sharp. It comes in a deep burgundy red, black, silver, while (white luggage?) and khaki. You can tell which one I like from the picture, right?
The Extended Trip Packing Case is 32.5 inches by 20.5 inches x 12.5 inches and weighs 10.6 lbs. It also costs $895; however, with as much traveling as I’ve been doing, I might pay that for something durable and light that lets me arrive at my destination with everything intact – including my shoulders.
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