S-Ply® leaf springs

S-Ply® leaf springs consist of layered and compressed UD (unidirectional) prepreg plies. The mechanical properties of an S-Ply® leaf spring may be adapted to customer requirements and application during production by orienting individual prepreg layers to each other. S-Ply® leaf springs offer superior properties to steel leaf springs in many applications.

Material properties

  • Unidirectional fibres The reinforcing fibres in the leaf springs consist of strictly parallel-oriented glass or carbon fibres that are not woven together. The fibres are not pre-stretched and not kinked. In contrast to metallic materials with an isotropic structure, they are direction-dependent and may therefore be aligned to form a material-specific design
  • Epoxy resin matrix Epoxy resin systems serve as binders. Their special composition ensures very good adhesion to the glass surface, resulting in optimal dynamic and electrical properties. The ratio of matrix resin and reinforcing fibres is formulated in such a way that all the advantages of the selected raw materials are used as a composite material.
  • The matrix takes on a number of important tasks. It fixes the fibre in the desired configuration and supports it against buckling under compressive stress. In addition, it has force-bearing function, thus transferring the forces into the fibres. The polymer matrix therefore plays a key influence on toughness and damage tolerance of the composites.
  • Tried and tested long-term strength The long-term strength of S-Ply leaf springs was tested by IMA Material Research and Application Technology Dresden in a Wöhler test. As a function of the deflection voltage, the resulting Wöhler curve indicates the number of tolerable load changes up to expected fatigue failure. Up to a load change of 108 cycles, fatigue strength is expected.

Geometries made to measure - from One-offs

We manufacture S-Ply® leaf springs as individual customised problem solutions - economicall thanks to flexible processes y in any desired quantity, including one-offs.

All geometries within the flat mould area are possible: Square and round geometries, drilled and slotted holes with counterbores and tapped threads. Mechanical processing of S-Ply® leaf springs is carried out on CNC-controlled saws, milling and drilling machines exclusively with diamond and carbide-tipped tools.

To reduce notching and shear stress during installation, we recommend reinforcing the clamping surfaces with glass fibre-reinforced laminate spacers GRL green.

Composites instead of steel

Our fibre composite material S-Ply® has many advantages over steel as a material for leaf springs:

High elastic energy storage capacity (low modulus of elasticity) with high mechanical strength.
  • Balanced spring behaviour, significantly greater specific spring effect, higher internal damping, 6 times greater elastic energy storage capacity compared to spring steel.
The individual prepreg layers may be oriented at defined angles to each other.
  • The mechanical strength of the component, especially against torsion, can be precisely controlled. Ideal adaptation of leaf spring geometry and material to the load.
Balanced ratio of mechanical strength to weight, high fatigue strength, corrosion resistance, notching impact strength, electrical insulation.
  • Enables mechanically and dynamically highly stressed constructions.

S-Ply®: Scotchply, improved

The fibre composite Scotchply™, developed and patented by 3M in 1954, has been processed into high-performance leaf springs by Prause Durotec since 1974. Today, leaf springs made of the same optimised fibre composite material are marketed worldwide under the protected product name S-Ply® by Prause Durotec.