Composite Springs for: Suspension Vehicles, Spacecraft Stage Separation, and Satellite Ejection on Orbit 2018-01-0150

SARDOU SAS has developed highly stressed composites parts for 36 years. SARDOU SAS and QUALITY INDUSTRIAL PRODUCT jointly invented and patented composite “C” springs in 1993. We have designed and tested “C” springs, giving an energy density of 1350 Joules per kilogram (compared to 300 Joules for steel springs). This energy density means a potential 78% weight savings! But in the last century, weight savings was not a must and platform managers were reluctant to use anything else than coil springs. So in 2002, in order to comply with their wishes, we have invented and developed composite coils springs. Composite coils springs are the best choice for McPherson suspensions. We have identified that the weak point, in composite coils springs, is its epoxy matrix. During heavy loading, the matrix undergoes micro cracking. Then, during repeated loadings, micro cracks propagate and merge, transforming the matrix into a fine powder. As a result, composite coil springs, using classic epoxy, were ruined after only 100.000 cycles or less. Based on this finding we have developed our matrix reinforcing technology called EPOSIL®, and achieved 2.000.000 cycles with the same spring design. Our composite coils spring technology, design, and matrix, is now under control. Nowadays, as weight savings is mandatory, this paper describes all the benefits of “C” springs and “S” springs for vehicles and spacecraft applications.