Optimal design and analysis of mono leaf composite spring by finite element analysis

A nine-leaf steel spring used in the rear suspension system of a light duty vehicle is analyzed by finite element method using ANSYS software. The finite element analysis results of stress and deflection are verified with the analytical solution and experimental results. It is proposed to replace the existing steel spring with composite spring. With the results of the steel leaf spring, a mono leaf composite spring made from E-glass fibre with epoxy resin matrix is designed and its geometry is optimized by finite element analysis. The design variables are the width and the thickness of the composite spring. The design constraints were stress (Tsai-Wu failure criterion) and displacement. The objective was to obtain a spring with minimum weight capable of carrying intended static external force without failure. The optimized spring will have its width decreasing and thickness increasing hyperbolically from the spring eye towards the axle seat. An approximate spring model is assumed and its analytical solution is also presented. Compared to steel spring, the optimized composite mono leaf spring has much lower stress and the spring weight without eye units is nearly 65%lower than steel spring.