We've reported before about various plans to improve the manufacturing of carbon fiber composites for use in mainstream automobile manufacturing. These efforts are among several automotive lightweighting approaches being tried to help cars meet federal fuel efficiency standards. Now the Australian company Carbon Revolution says it has made the first one-piece, all-carbon fiber composite wheel for cars and planes.
The CR-9 wheel is constructed from continuous carbon fiber. Both front and rear wheels have a 19-inch rim diameter. The front wheel has a rim width of 8.5 inches and weighs 15.73 pounds. The back wheel has a rim width of 12 inches and weighs 18.15 pounds. Carbon Revolution says the wheels are 40 percent to 50 percent lighter than typical automotive OEM aluminum wheels. A quick check around the Web gave an average weight of about 25 pounds for an aluminum car wheel of roughly the same size.
The one-piece CR-9 front wheel weighs 7kg (15.73 pounds), has a rim diameter of 19 inches, and attaches to metal hardware with a patented joint system under dynamic loading conditions. (Source: Carbon Revolution)
A patented bolted joint system is used to attach composites to the CR-9's metal hardware under dynamic loading conditions. As we've reported before, mixed materials attachment methods are an ongoing problem in newer aerospace designs that combine metals with carbon fiber composites, most recently in the Airbus 380 wings. Carbon Revolution says its joint system is as highly engineered as the wheel's composite structure.
CR-9 wheels are designed using computational modeling techniques, which include full vehicle dynamic modeling and finite element analysis (FEA). Carbon Revolution says its computational simulations are so closely correlated to actual wheel behavior that product development timeframes are shortening. (You can watch a video of CR-9 impact tests simulating a pothole at the bottom of the post.) Because the behavior of fiber laminates is much more complicated compared to cast or forged metals, the company is working with FEA partners to develop improved methods for accurately modeling carbon fiber properties.
Although there's a wealth of information for longstanding aerospace applications, putting this technology to use in automotive manufacturing is a challenge. For example, recently renewed US Department of Energy funding for automotive lightweighting emphasizes research and development in the predictive modeling of carbon fiber composites, including the development and validation of modeling tools to optimize carbon fiber composite performance and cost-effectiveness. (See: Automotive Lightweighting Funding Renewed by White House.)
The process for manufacturing CR-9 wheels combines aerospace manufacturing rigor with the efficiency, process controls, and automation of high-volume automotive production lines. By 2013, Carbon Revolution hopes to have certification for TS16949, the ISO technical specification detailing the development of automotive quality management systems. Its approach has attracted funding from the Australian government's $5.4 billion New Car Plan.
The company began as an independently run R&D program collaborating with university research teams working on Formula SAE (Society of Automotive Engineers) student designs. Vehicles in the 2004 competition used the first composite wheels designed by Carbon Revolution's founders. Its founders and employees include senior engineers in chassis development and drive train functions from automotive OEMs, senior manufacturing executives from component suppliers such as Bosch, former employees of Boeing's Phantom Works, and industrial composites manufacturing specialists. The company also maintains technology development and product testing relationships with Deakin University and RMIT in Australia.
That sounds more like a road failure than a pothole. Glad the roads where I live are better maintained. I doubt if many design/material combinations could survive an encounter with that cavity unharmed.
Well, my question is are the weight reduction goals to reduce the entire vehicle's weight, or just the unsprung weight, and how those two differing strategies impact fuel efficiency. Reducing unsprung weight is always a good thing, mostly for NVH. Reducing wheel/tire weight does have some positive MPG impact, but mostly during accceleration, it actually can work the other way during deceleration, where a heavier wheel/tire can help maintain momentum. Using carbon in a wheel is a very challenging application...perhaps putting carbon in other areas to reduce weight might be much more cost effective way to the same effect, perhaps using carbon in suspension components, thus satisfying some of the total weight reduction goals AND unsprung weight goals, although admittidly not as dramatic as carbon wheels.
Yep, actually, that's the stretch of road I was thinking of. So many people I worked with had their aluminum rims destroyed on the way back from meetings in Detroit. And guys coming back with a sore head because they hit the roof during the ordeal.
I guess maybe the carbon would be safer then...after both rims plough into the hard edge pot hole, smash into a tangled mess of shards and fibres, you could glide to a stop on the underbelly or your car since the chassis would now be about flush with the road surface adjacent to the pot-hole.
But point taken about the resin choice that would have some "give" to it.
Sven...the durability of carbon fiber is in the resin system chosen. When extreme stiffness is the design requirement, the proper resins are brittle. When tension/compression strengths are the requirement, a more resilient resin can be used.
As for cost...I'd expect 2-4x the cost of aluminum, depending on the production quantity.
kf2qd, carbon weighs a heck of a lot less than steel: the strength-to-weight ratio most often quoted is 4-5x, which is the main point for using it in automotive lightweighting as the article mentions. The video at the bottom of the article shows the pothole impact test.
Chuck, once again no pricing information was available, but I'd be very surprised if it cost the same or less. TJ, I think calling diamonds a form of carbon is stretching the definition in terms of what's practical in a manufacturing sense.
The pictures of the aluminum wheel dented at 50mph on the pothole simulation compared to the 60mph without effect looks good.
Sven is still right, when these wheels fail, they will likely fail miserably. But it appears they won't fail easily. Of course, I lived in Detroit for a while and very little made it through the tire killer on southward I-94 - a pothole about 3 feet long and at least a foot deep (has since been fixed). There were cars lined up along the road just past that pothole. I wonder how this would do against something like that?
Having read many questions about alternate materials in some custom and kitcar forums, How does the weight of the carbon wheel compare to that of a steel wheel? And how well will they stand up to the standard North American pothole? While aluminum and carbon fiber do have their place, often it is necesssary to add weight to achieve the desired strength of the original steel wheel. Maybe not as pretty...
While they may have a certain "sex apeal" it would seem that this application could leave something to be desired in terms of the abuse the wheels have to endure as a normal part of their life cycle.
Gee, I don't know - why would you pay the price for carbon and then not show-it-off? Isn't that part of the glamour? I do know that people have added pigment to the resin on some carbon assemblies. It is, after all FRP, so you can make the plastic any color you want. I'm much more impressed with the fastenings. So far, if you want to connect a carbon fiber assembly to something, you must either bond it, or use fasteners which typically create such high point loads that the carbon assembly fractures. There is great potential in this technology though I'd guess cost will be the major factor in implementing it.
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