Audi aims to use fibreglass coil springs to reduce suspension weight by 40% and help save fuel.

CAR COMPANIES ARE looking for more ways to reduce the weight of their vehicles in an effort to make even the tiniest of fuel savings. To that end, Audi has announced it will be adding “lightweight suspension springs made of fibre-glass reinforced polymer (GFRP) in an upper mid-size model before the end of the year”.

According to Audi, the GFRP looks quite different to a coil spring (see main picture), “It is light green, the fibre strand is thicker than the wire of a steel spring, and it has a slightly larger overall diameter with a lower number of coils. Most importantly, however, it is some 40% lighter. Whereas a steel spring for an upper mid-size model weighs nearly 2.7 kilograms, a GFRP spring with the same properties weighs just 1.6 kilograms. Together the four GFRP springs reduce overall weight by roughly 4.4 kilograms, half of which is unsprung mass.

How are they made?

Audi says: “The core of the springs consists of long glass fibres twisted together and impregnated with epoxy resin. A machine wraps additional fibres around this core — which is only a few millimetres in diameter — at alternating angles of plus and minus 45 degrees 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-degrees Celsius.

“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. Last but not least, production requires far less energy than the production of steel springs.”