Carmaker Audi (Ingolstadt, Germany) reports that is introducing 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, which Audi developed in collaboration with an Italian supplier, looks different than a steel spring: It 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 smaller number of coils. However, it is 40 percent lighter. Whereas a steel spring for an upper mid-size model weighs nearly 2.7 kg (6.0 lb), a GFRP spring with the same properties weighs just 1.6 kg (3.5 lb). Together, the four GFRP springs reduce vehicle weight by 4.4 kg (9.7 lb), half of which pertains to the unsprung mass.
“The GFRP springs save weight at a crucial location in the chassis system. We are therefore making driving more precise and enhancing vibrational comfort,” says Dr. Ulrich Hackenberg, member of the Board of Management for Technical Development at AUDI AG.
The core of the springs consists of long glass fibers twisted together and impregnated with epoxy resin. This structure is then filament wound at alternating angles of ±45°. These tension and compression plies mutually support one another to optimally absorb the stresses acting on the component. Each spring is cured in an oven at more than 100°C/212°F.
Other benefits of the springs cited by Audi include: Easy tuning, corrosion resistance, chemical resistance, reduced energy consumption during manufacture.