- Glass fibre-reinforced polymer springs replace conventional steel equivalents
- 40 per cent weight saving contributes to overall reductions and cuts unsprung weight for faster suspension reaction and better road contact
- Market launch in autumn 2014
Audi is investing heavily in travelling lightly to boost efficiency. New polymer suspension springs that reduce weight by 40 per cent are further proof that no detail is too small to escape scrutiny as part of the Vorsprung durch Technik brand’s ‘ultra’ programme.
The new, lightweight suspension springs are made of glass fibre-reinforced polymer (GFRP), and will appear in an executive class Audi model before the end of the year. Developed in collaboration with an Italian supplier, their light green colouring immediately sets them apart from conventional steel springs, and they have thicker fibre strands and a slightly larger overall diameter with a lower number of coils. Most importantly, they are some 40 per cent lighter than their more ‘traditional’ counterparts.
Whereas a steel spring for an executive class model weighs nearly 2.7 kilograms, a GFRP spring with the same properties weighs approximately 1.6 kilograms. Together the four GFRP springs therefore reduce the weight by roughly 4.4 kilograms, half of which pertains to the unsprung mass, helping the suspension to react more quickly to changes in the road surface and to absorb imperfections more effectively.
“The GFRP springs save weight at a crucial location in the chassis system. We are therefore making driving more precise and enhancing vibrational comfort,” said Dr. Ulrich Hackenberg, Member of the Board of Management for Technical Development at AUDI AG.
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.
Audi uses the ‘ultra’ designation to encompass the very latest technological advances which enhance efficiency in every sphere from lightweight construction to engine development. The philosophy is embodied in the UK by A4, A5 and A6 TDI ‘ultra’ models capable of returning up to 67mpg with emissions of as little as 109g/km.