Investigation on the effects of changing automotive vehicles leaf springs from steel to hybrid polymer composite leaf springs

Abstract

Weight reduction is a critical factor in the vehicles and numerous researchers worked on better materials and design optimization to achieve that goal. This paper is focused to design a natural fibre reinforced hybrid polymer composite mono leaf parabolic spring to replace the existing steel multi-leaf semi-elliptical spring in an attempt of reducing the unsprung mass and to investigate its characteristics. The spring so designed is analyzed for its deflection and stiffness, by Virtual work method, whose complex integral was solved numerically by Gauss Quadrature. Along with this, SolidWorks was used to construct a model and ANSYS tests were used to compute the deflection, analyze the stress pattern and verify that the fail proof condition is met. Subsequently, three prototypes of the springs were fabricated by hand lay-up method. These springs were subjected to a static load test which results in deflection values similar to that of laminated steel springs with an appreciable 83 percent weight reduction. Modal Analysis conducted ensures that the fundamental frequencies of different modes are conveniently away from values of human discomfort and also from the nominal driving engine speed of 2000 rpm. The responses to harmonic disturbances which were studied experimentally, analytically and by ANSYS which indicates that vibration amplitudes due to average road undulations are under control, limiting the amplitude within 12 mm. The newly designed spring shall be recommended as a potential replacement, which can further be augmented by future works to be carried out on pot holes and studying the force transmitted on to the vehicle.