MOTOGP » Ducati’s carbon fibre MotoGP chassis.

Getting back (at long last) to Waz's question about layup directions...I want to orient fibers to use their full capability and not waste material reacting loads that aren't there. E.g., for a beam in bending (think I-beams or swingarms), I'll react the tensile-compressive loads with fibers along the long axis on the top and bottom of the beam, and just have enough material in between to react lower shear loads. They do this usually with structural foam or hexagonal-celled paper, funny enough, but I could also orient my fibers at 45 degrees to the faces and turn the shear load into a tensile-compressive load.

MOTOGP » Ducati’s carbon fibre MotoGP chassis.

Sometimes people use a woven cloth instead of unidirectional tape. This isn't as strong in a given direction because the fibers aren't as straight as in prepreg, plus they typically have to apply the epoxy resin themselves which can be tricky (proportions of fiber to matrix are pretty critical). It can be easier to work with, though, and has the capacity to take unpredictable loading better than unidirectional layups. cloth better approximates the properties of metal in that regard. Metals have essentially the same properties in all directions. They are also good at locally deforming without failing to turn high stresses into lower stresses. Carbon ain't.

MOTOGP » Ducati’s carbon fibre MotoGP chassis.

The resin also distrubutes loads between the fibers. A single fiber may only be 0.005 mm diameter, so it takes thousands of them for a structure. Typically, the fibers come already assembled into neat rows in a single layer of some useful width, pre-impregnated with the right amount of epoxy resin ("prepreg" tape). They'll cut pieces from the roll and lay them in desired orientations (more on that in a sec) on a mold until they get the thickness they desire in every location. The whole thing is then baked together under pressure then inspected for voids. If they find any that are too big, they throw away the part and start over.

MOTOGP » Ducati’s carbon fibre MotoGP chassis.

The carbon fiber is also less dense than the other materials (1.8 g/cc versus 4.5, 7.8 and 2.7). If we had equal-sized bars made from these materials, the carbon would carry 5x the tensile load of the titanium before snapping AND weigh less than 1/2 as much. Another way of looking at it - you need less carbon fiber than you do metal to carry a given tensile load. Real loads in structures, however, aren't purely tensile. There are compressive, shearing and torsional loads to deal with. To allow carbon fiber to react these loads (and to have them hold a constant shape), they are embedded in a resin matrix that supports them and prevents them from buckling as readily.

MOTOGP » Ducati’s carbon fibre MotoGP chassis.

No problem at all, Waz. I think we're all fans or we wouldn't be here. In composites, we have to remember that bare fibers can only take a tensile load (pulling, as with a rope). If you apply a load in any other direction, they'll buckle very easily. The thing about carbon fibers that everyone loves is that they're REALLY GOOD at taking huge tensile loads before they fail. The ultimate strength of a carbon fiber is on the order of 5000 MPa versus 1000 MPa for common titanium alloys, 750 MPa for common steel alloys and 500 MPa for aircraft aluminum (talking in rough values). ** Uh-oh, running out of room...multi-part post coming up (sorry in advance, all). **

MOTOGP » Ducati’s carbon fibre MotoGP chassis.

I don't think anyone's saying there's nothing new, Waz. We're saying it's a technology that has been tried before but for some reason hasn't caught on. We're interested to know (and are having fun speculating) how Ducati might be applying this technology differently than in previous attempts and whether they've seen an advantage others haven't yet. BTW, these particular materials don't seem to be that different now than when Mr. Britten used them. I'm looking at some carbon/graphite and epoxy properties in my 15-20 year old handbooks and see a similar range of moduli, strengths and densities available for fiber and matrix as I see on current manufacturers' sites (Toray, Dow, etc).

MOTOGP » Ducati’s carbon fibre MotoGP chassis.

Point taken, Tell it, and a good point it is. You have to respect its limitations. It's fascinating to watch these materials being applied in new situations and tested to their limits. Remember the oneAustralia yacht that sank in 1995 during America's Cup trials? The de Havilland Comet of the late 40's is another example of learning the tough way how to use new materials or not-so-new materials in a different way. I still contend that they've either hired-in or farmed-out for the composites expertise to get things right on their first go with it. Every tenth counts, and hopefully they'll be able to explore the limits without incurring any catastrophic failures.

MOTOGP » PIC: Rossi glowing in the dark.

Anyone know if they all use carbon brakes?

MOTOGP » Where might Melandri, Toseland have finished?

If JT was actually demoralized and rode slower as a result of his farming incident, then the speculative data becomes especially useful to Poncharal. He can use it either to re-motivate him for Motegi ("If we stay on track and keep pushing hard we can be way up here.") or else pushing him out the door ("Why did you slow down? Am I not paying you to ride fast? Why do you insult me so?!?"), depending on his agenda. See, it's useful data.

MOTOGP » Ducati’s carbon fibre MotoGP chassis.

@ Tell it: load and stress aren't the same thing. If a given material is used on a fighter or a bike, then it's (hopefully) not loaded beyond the material's allowable limit. Stresses are probably lower on the airframe because it has a much longer service life - higher cyclic stress means shorter life. I suspect the use of titanium structure you describe has to do with (1) damage tolerance and durability, (2) ease of field repair and (3) getting the loads into and out of FRP composite structure that is there. This is also likely why alloy is visible on the swingarm. Point-loads have to be distributed over a broad area in FRP's to avoid local delamination, so metal fittings are bonded in.