Influence of the geometry of a CFRP leaf spring on its mechanical response

Abstract

Carbon fibre-reinforced polymer (CFRP) laminates are replacing traditional materials in numerous applications in which high specific strength and stiffness are sought. One example could be the use of composite leaf springs for lightweight structures in transport, which should be designed taking into account their bending response. The main objective of this work is to study analytically and numerically the influence of the geometry on the mechanical response of a mono leaf spring under the hypothesis of linear behaviour. With this scope, the performance of a CFRP mono leaf spring is observed considering four different geometries: cubic, parabolic, arc of circumference and elliptical. A linear-elastic study is carried out to examine the influence of the spring shape on its flexural behaviour in terms of the load transfer as well as the apparent bending rigidity, natural frequency and buckling load. Three-point bending tests are performed with parabolic specimens manufactured from unidirectional CFRP laminates for validating the assumption of linear response for three different thicknesses of the cross-section. The experimental results confirm the linear-elastic response of the samples, what allows theoretically estimating the stiffness and the stress state of the spring.