AndyB

Our Z is so High-Tech it made a recent engineering newsletter.

Check it out:
-----------------------------------------------------

"Crashworthy" carbon-fiber drive shaft eliminates adhesives
By Joseph Ogando

Carbon-fiber drive shafts have graced performance cars for years, reducing weight and eliminating vibrations. But concerns about crash performance and costs have, with a few exceptions, kept them out of production vehicles. Toray Composites America Inc. has found ways to address both issues with an improved shaft design that features a new winding pattern and simplified joining technology.

According to Tetsuyuki Kyono, director of Toray's composites development center, these "crashworthy" epoxy-and-carbon fiber drive shafts offer an energy-absorbing progressive fracture mode not found on previous carbon-fiber shafts.

To bump up the shaft's ability to absorb axial crash forces, Toray engineers added an extra layer of helical windings to the shaft ends, sandwiching it between an inner hoop layer and an outer lapping layer. During a crash, a flange on the drive shaft's steel yoke wedges itself between these inner and outer layers in what Kyono describes as a "wedge effect." At first, the wedging of the yoke causes only a delamination of the inner and helical layer. Later on, as a sufficiently serious crash progresses, the tube would crack around the yoke.

Kyono contrasts this progressive fracture with the sudden buckling and fracture of conventional carbon fiber shafts. And he cites a 55-kph crash test results in which the new shaft design reduced peak axial compression loads to just 10 kN from 330 kN with a conventional carbon fiber

Another key to the crashworthy drive shaft system is its joint with the yoke. Kyono notes that previous carbon-fiber shafts tended to be joined to their yokes with adhesives--which not only increased assembly cost but also axially constrained the yokes during crashes. Toray engineers, however, eliminated the need for adhesives by coming up with a robust press-fit joint. It relies on serrations on the outer diameter of the yoke to grip the inner diameter of the shaft. The interference between serrations and shaft was carefully optimized with the help of finite element modeling. Kyono say the resulting joint easily meets a 2,000 Nm torque specification--both in static and fatigue tests.

Toray's carbon-fiber shafts, which Kyono says weigh 40-50% less than comparable two-piece steel designs, have started to appear on some production vehicles, including the Mitsubishi Montero, Nissan 350Z, and Mazda RX-8.

Anarchy

Thanks

micmicmotorbike

iTrader: (13)

one of the reasons i realized this was a serious, and true sports car.

KrazY-2K

The RX-8 has one also? Interesting.

sschmuve

iTrader: (1)

The RX-8 also shares our auto dimming rearview mirror.

Nismobilized

wow. that's technobabble. this article is great.

few questions: does "absorb[ing] axial crash forces" mean the carbon fiber shaft is good at absorbing impact longitudinally? or longways? it probably does, cuz absorbing it sideways is kinda useless.

"Kyono say the resulting joint easily meets a 2,000 Nm torque specification--both in static and fatigue tests." what is a static test?

PhoenixINX

and we share it with nearly every GM on the road.

teasack

A static test applies an increasing load until failure, where as the fatigue test cycles the part through many repetitions usually well below the materials utlimate strength until failure. In both cases the part fails but the tests are measuring different material characteristics: ultimate strength vs fatigue strength.

JeffR116

That's Awesome. I know someone that works at the Toray factory less than 5 minutes away from my house. I had no idea they developed the cf shaft for the Z.