Design and Analysis of Composite Structures for Automotive Applications

10Composite Leaf Springs

10.1 Longitudinally Mounted Leaf Springs for Solid Axles

10.1.1 Predominantly Bending‐Loaded Leaf Springs

The leaf type of spring is currently the most widely developed concept of the composite springs. This type of spring has been used for a long time, but industrial application started a decade ago. Leaf springs made of steel with a wheel‐guiding function have long been used extensively for the transportation of vehicles. Analogously, leaf springs, made of glass fiber‐reinforced plastic, are thin strips that exert a spring force when bent. There are several types of leaf spring with different mechanical properties and suspension functions. A brief comparison of different concepts for leaf springs is presented in Table 10.1 (Kobelev et al. 2015). At a low density of 1.9 g cm⁻³, excellent fatigue resistance and low longitudinal modulus of elasticity of 40 GPa, the fiberglass permits high elastic strain and low spring rate that improves vehicle comfort (Kelly and Zweben 2000, Vol. 2, Polymer Matrix Composites).

Table 10.1 Comparison of different concepts for leaf springs (Kobelev et al. 2015 ).

Leaf spring with constant cross‐section	Single layer elliptic leaf spring	Multileaf elliptical spring	O‐elliptical leaf spring	Leaf‐tension springs
Spring rate	Constant		Linear‐continuous or multilinear progressive	Bilinear progressive	Linear‐quadratic progressive
Non‐linear spring rate adjustment	–		By changing the cross‐sections		Adjustable by geometry ...