Coil spring from GFRP
No, springs made from Glass-Fibre Reinforced Plastic are nothing special in motor vehicle suspension. Already the 1981 Chevrolet Corvette was given these instead of steel springs. In
the truck field, this spring has also been in service for some time now.
Indeed, one difference to the above shown spring must be emphasised: Up to now, this material has always been used for leaf-springs. A coil spring made of GFRP, is in fact, something new, particularly in mass-
production. Audi has got together with an Italian supplier and wants to see them in the upper middle class range in the autumn of 2014.
Spring-steel is traditionally heavy. As a rule, the attempt to try to reduce weight here, ended in a small fiasco. In addition, not only the choice of material but also the nature of the surface of steel springs, is of great
importance, since the highest strain is on the surface layer and if a spring is going to break, it'll start here.
The most important argument in favour of GFRP coil springs is however, the saving of about 40 percent in weight, compared with those mostly made of chrome-, silicon- or chrome-vanadium steel. In the case of the
suspension, weight-saving brings double the advantage, because at the same time, the unsprung masses are reduced.
Perhaps the light green colour is not that important, even more so, the internal composition of twisted, impregnated glass-fibres. Around this core, which is only a few millimetres thick, further layers of the same material
are wound alternately at an angle of 90° to each other. Finally, the hardening process takes place in an oven at a temperature of 100°C.
Even though the two springs shown above have roughly the same amount of coils, because of the thicker GFRP-wire, it may quite easily have fewer. The springs being compared here, differ in weight from 2,7 kg to just
about 1,6 kg. Thereby, in the case of the GFRP springs, the hardening process e.g., requires much less energy than the high-temperature surface decarbonisation treatment of the steel springs.
Coils springs are found in almost all motor cars, right up to the light-delivery-van class. Thus, an enormous area of application for the new springs has been opened up. Once the demand has been satisfied, one could
continue with making GFRP-stabilizers, although in this case, the fact that tubing is used for the manufacture, may make it more difficult to achieve a weight reduction. 07/14