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Audi to use suspension springs of glass fiber-reinforced polymer instead of steel for ~40% weight savings

30 June 2014

Audi will introduce new, lightweight suspension springs made of glass fiber-reinforced polymer (GFRP) in an upper mid-size model before the end of the year. The GFRP spring is some 40% lighter than a steel spring.

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The GFRP spring (left), which Audi developed in collaboration with an Italian supplier, even looks different than a steel spring (right). The GFRP unit is light green, the fiber strand is thicker than the wire of a steel spring, and it has a slightly larger overall diameter with a lower number of coils. Click to enlarge.

Whereas a steel spring for an upper mid-size model weighs nearly 2.7 kilograms (6.0 lb), a GFRP spring with the same properties weighs just approximately 1.6 kilograms (3.5 lb). Together the four GFRP springs thus reduce the weight by roughly 4.4 kilograms (9.7 lb), half of which pertains to the unsprung mass.

The core of the springs consists of long glass fibers twisted together and impregnated with epoxy resin. A machine wraps additional fibers around this core—which is only a few millimeters in diameter—at alternating angles of plus and minus 45˚ to the longitudinal axis. These tension and compression plies mutually support one another to optimally absorb the stresses acting on the component. In the last production step, the blank is cured in an oven at temperatures of over 100 ˚C.

The GFRP springs can be precisely tuned to their respective task, and the material exhibits outstanding properties. It does not corrode, even after stone chipping, and is impervious to chemicals such as wheel cleaners. Production requires far less energy than the production of steel springs.

The GFRP springs save weight at a crucial location in the chassis system. We are therefore making driving more precise and enhancing vibrational comfort.

—Dr. Ulrich Hackenberg, Member of the Board of Management for Technical Development at AUDI AG

June 30, 2014 in Brief | Permalink | Comments (8) | TrackBack (0)

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Comments

OK but this is not really new. GM has been using glass fiber-reinforced polymer (GFRP) springs in the Corvette for at least a decade. I do wonder why they use glass instead of carbon fiber which is even stronger for the mass.

Corvette uses leaf springs, not coil.

http://www.edmunds.com/auto-shows/detroit/2013/2014-corvette-will-retain-leaf-spring-suspension.html

Coil springs made of this material is new.

Rustless springs and other components could make a light weight e-car, with future long lasing batteries, last 20 to 25+ years with minimum maintenance.

Since it may cost 20% or so more, many will object, even if it consumes a lot less energy and produces less GHGs.

I suggest using this material for car seat cushions, seat springs (Banks springs) and seat mounts,for more weight savings and fire retardency to boot.

SJC

I know that the Corvette uses leaf springs. They have 2 cantilever transverse leaf springs, 1 for the front, 1 for the rear. It is a relatively clever system that keeps the unsprung weight down. However, I would argue that a spring is a spring and they managed to replace what would have been a piece of steel with a lighter material that is also corrosion resistant.

I don't think mechanical engineers would say "a spring is a spring", if that were the case GM would have gone with coil a long time ago. No sense arguing a small point, I think any spring made this way is amazing.

SJC

Not a big deal but just for the record, I am a practicing Mechanical Engineer with 3 degrees including a doctorate in Mechanical Engineering from MIT along with a degree in Physics. I have designed springs and taught others how to design springs. I used to teach the senior design class in the local University and still am the adviser for students competing in the FormulaSAE competition so I know a fair amount about springs and suspensions.

sd

Congratulations. I have lately wondered about the credentials of some on this blog with more hauteur than politeness.

I just wonder whether the new spring technology is is use-it-and-throw-it-away concept, which is not all bad, since suspension adjustment is an art which some body shop men think they can scalp you on.

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