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SARDOU SAS has developed highly stressed composites parts for 35 years. SARDOU SAS and QUALITY INDUSTRIAL PRODUCT invented composite coils springs in 2002. Developing composite coils springs, we have faced a big challenge, how to increase the short life expectancy of this highly stressed structure? We have identified that the weak point, in composite coils springs, is its epoxy matrix. In fact, during heavy loading, the matrix undergoes micro cracks. Then, during fatigue, micro cracks propagate and merge, transforming the matrix into a fine powder. The composite coil suspension springs, using, classic epoxy, where ruined after only 100,000 cycles in the best cases. The fact to integrate “functionalized silica aggregates”, in the matrix, enable the springs to exceed 1,000,000 cycles, with the same spring design. In addition, the spring stiffness has increased by 6% and the thermal set has reduced by 1.6%.

This paper presents information on new technology which has made the Composite Coil Spring a practical Reality. The light weight and low cost nature of this novel component presents very interesting possibilities for reducing the weight of automotive models. The experimentation with composite materials which was focused on developing practical components with viable manufacturing methods began in our company 1983. The first episode was with very strong torsion members for truck applications. This was followed by development of a unique “C” spring design in 1993 (reported in SAE paper 2000-01-0100). This paper deals with the new successor to these earlier designs, the “Composite Coil Spring”. This paper identifies the manufacturing process that has been developed and patented to provide composite Coil springs cost effectively. The paper also presents the physical properties of the springs which are made from thermoset Epoxy, and E type glass fibers.

This paper show some examples of our C springs manufacturing, realization, testing and optimization features. Composite C Springs have been developed by our company Since 1993. We will start our presentation by an analysis of reasons why Composite Compression Springs (patented) perform well compared to leaf springs. Then we will give examples of some development programs we have successfully carried out from study up to vehicle road testing. The C Springs have been tested in static measuring bench, in fatigue and in relaxation machine. C Springs have (and are), also road tested. More than hundred of thousand kilometers have been achieved with success (near exhaust pipe). We will present examples of spring integration giving a dramatic weigh reduction, as well than ride handing improvement. We will also introduce cost notions showings that Composite Compression Springs save money as well as weight on a vehicle.