It is lighter, stiffer, and transmits torque better than the two-piece aluminum (Note - this was an error as the GT500 was using steel and not aluminum) shaft it replaces. The carbon fiber is not so much for lightness as stiffness. It was the only way to get the bending frequency of the shaft above the rotational speed driven by the 200-mph vehicle speed, according to its lead engineer, Brian Zorman.
The '13 one-piece carbon-fiber driveshaft was the only way to accommodate the new GT500's higher torque and road speed. This saves nearly 15 pounds, can transmit 36 percent more torque, and eliminates the friction of the center support bearing used in earlier GT500s.
All told the steel inserts cost more than the tube, leading Jamal to joke, "We managed to design steel that's more expensive than carbon fiber!"
A driveshaft is a rotating shaft that transmits power from the engine to the differential gear of a rear wheel drive vehicles. Driveshaft must operate through constantly changing angles between the transmission and axle. High quality steel (Steel SM45) is a common material for construction. Steel drive shafts are usually manufactured in two pieces to increase the fundamental bending natural frequency because the bending natural frequency of a shaft is inversely proportional to the square of beam length and proportional to the square root of specific modulus. The two piece steel drive shaft consists of three universal joints, a center supporting bearing and a bracket, which increase the total weight of a vehicle. Power transmission can be improved through the reduction of inertial mass and light weight. Substituting composite structures for conventional metallic structures has many advantages because of higher specific stiffness and higher specific strength of composite materials.
Composite materials can be tailored to efficiently meet the design requirements of strength, stiffness and composite drive shafts weight less than steel or aluminum of similar strength. It is possible to manufacture one piece of composite drive shaft to eliminate all of the assembly connecting two piece steel drive shaft. Also, composite materials typically have a lower modulus of elasticity. As a result, when torque peaks occur in the driveline, the driveshaft can act as a shock absorber and decrease stress on part of the drive train extending life.
Merits of Composite Drive Shaft
1. They have high specific modulus and strength.
2. Reduced weight.
3. Due to the weight reduction, fuel consumption will be reduced.
4. They have high damping capacity hence they produce less vibration and noise.
5. They have good corrosion resistance.
6. Greater torque capacity than steel or aluminum shaft.
7. Longer fatigue life than steel or aluminum shaft
When the length of a steel drive shaft goes beyond 1500 mm, it is manufactured in two pieces to increase the fundamental natural frequency, which is inversely proportional to the square of the length and proportional to the square root of the specific modulus. The nature of composites, with their higher specific elastic modulus, which in carbon/epoxy exceeds four times that of aluminum, enables the replacement of the two-piece metal shaft with a single-component composite shaft which resonates at a higher rotational speed, and ultimately maintains a higher margin of safety. A composite drive shaft offers excellent vibration damping, cabin comfort, reduction of wear on drivetrain components and increases tire traction. In addition, the use of single torque tubes reduces assembly time, inventory cost, maintenance, and part complexity
Since carbon fiber epoxy composite materials have more than four times specific stiffness of steel or aluminum materials, it is possible to manufacture composite drive shaft s in one-piece. The composite drive shaft has many benefits such as reduced weight and less noise and vibration
Graphite composites (graphite fibers/composites are sometimes called carbon fibers) are ideally suited for applications where high stiffness and low weight is required. Most metals used for structural applications have very similar specific stiffness, which is around 100 x 10^6 psi. If an application demands high stiffness and lightweight, graphite composites are the only material of choice.
Examples are:
Spacecraft structure
Aircraft structure
Drive shaft for trucks and high performance vehicles
Machinery rollers
Sail boat mast and boom
Bicycle frame
Machinery components that experience high acceleration & require stiffness & precision