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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%.

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.

A tractor-trailer at 1/10 scale has been tested in the Max Sardou Wind Tunnel (MSWT). This model is with four axels and free rotating wheels. We have produced 16 very different configurations. Each configuration has been tested in line (yaw = 0°) and with 5° of yaw (32 sub configurations); For each configuration, we have mesured six components properties of the model at low speed (33,5 m/s), with stationary and with moving ground; and then, at high speed (51 m/s), also with and without moving ground. So, we get 4 groups of 32 measures per type of measurements. Population of each group seems reasonably big enough in order to justify a statistical analysis of the ground motion effect and of speed of the test. In order to help this analysis, we have add for two configurations Reynolds tests (between 17 and 51 m/s with 5 m/s steps). These Reynolds tests have been conducted in belt on and belt off mode.

SARDOU SAS has invented in 1992 composite “C” springs (patented in 1993), these springs where offering a high energy density of 1350 joules per kilogram (compared to 300 for steel springs). This huge energy density means a potential 78% weight savings! But in the last century, weight saving was less important and platform managers were reluctant to use anything other than coil springs. So, in 2002, in order to comply with their wishes, SARDOU SAS invented composite coils springs. Easy to fit in standard suspensions, Composite coils springs are the optimum choice for McPherson-strut suspensions. As weight saving is now mandatory, composite springs, are the best choice for automotive suspensions, offering a 50% weight saving compared to steel. A Joint Venture, between SARDOU and SOGEFI Suspensions SA called S.ARA, was created in 2008 in order to mass produce composite coils springs; the official Start Of Production happen in 2014 for AUDI.