Fatigue Studies on Composite Eliptic Spring Elements for Automotive Front Suspension

Composite Elliptic spring elements were subjected to fatigue studies. A common trend of mild stiffness reduction during the initial stages of fatigue tests followed by a higher stiffness reduction rate during the intermediate stage (103-105 cycles) was observed. Above 105 cycles the stiffness reduction was found to be less severe. The fatigue performance of the spring elements having UDR configuration was always found to be poor compared to the ones having UDR/WRM laminated type-1 configurations. The spring elements having CTBN modified matrices were found to give superior fatigue performance than the unmodified matrix spring elements. The fatigue studies reveal that the upper limit of the deflection should be only 25 mm. At 30 mm deflection levels the stiffness reduction of both the spring elements were observed to be very severe. The spring element having 15% CTBN modified matrix and laminate type-1 configuration gave the best results with respect to the fatigue characteristics. The stiffness reduction at the end of 1 million cycles was found to be 22 %..