Mono Composite Leaf Spring for Light Weight Vehicle – Design, End Joint Analysis and Testing

Abstract

The automobile industry has shown increased interest in the replacement of steel spring with fiberglass composite leaf
spring due to high strength to weight ratio. Therefore; the aim of this paper is to present a low cost fabrication of
complete mono composite leaf spring and mono composite leaf spring with bonded end joints. Also, general study on the
analysis and design. A single leaf with variable thickness and width for constant cross sectional area of unidirectional
glass fiber reinforced plastic (GFRP) with similar mechanical and geometrical properties to the multileaf spring, was
designed, fabricated (hand-lay up technique) and tested. Computer algorithm using C-language has been used for the
design of constant cross-section leaf spring. The results showed that an spring width decreases hyperbolically and
thickness increases linearly from the spring eyes towards the axle seat. The finite element results using ANSYS software
showing stresses and deflections were verified with analytical and experimental results. The design constraints were
stresses (Tsai-Wu failure criterion) and displacement. Compared to the steel spring, the composite spring has stresses
that are much lower, the natural frequency is higher and the spring weight is nearly 85 % lower with bonded end joint
and with complete eye unit.