S-Ply® leaf springs



S-Ply® is the registered name for composite leaf springs that are manufactured by Prause Durotec.

The reinforcing material has a strictly parallel-oriented, non-interlaced glass or carbon fibre structure. The fibres are neither pre-stretched nor bent. In contrast to metallic materials with an isotropic structure, they are direction dependent and therefore can be aligned to suit the material structure.


Epoxy resin compounds are used as binding agents. Their special balanced composition ensures high adhesion to the glass fibre surface, resulting in optimum dynamic and electrical properties. The ratio of matrix resin and reinforcement fibres has been chosen to profit from all of the benefits offered by the raw materials selected to form the composite material.


The matrix fulfils a number of important tasks. It provides fixing for the fibre in the desired arrangement and supports it against buckling when under compressive stress.  In addition, it has good load carrying and transmission properties, thus it directs the forces applied into the fibres. Hence, the polymer matrix has a decisive effect on the toughness and the tolerance to damage of the composite materials.


S-Ply® leaf springs are stacked UD–pre-pregnated layers that are pressed together. The mechanical properties of S-Ply® leaf springs can be adapted to customers’ needs by the orientation of the different pre-pregnated layers, to one another, during manufacturing.


CNC-controlled saws, milling- and drilling machines with the exclusive use of diamond and carbide cutting tools are used for the machining of S-Ply® leaf springs.


The key characteristics of high performance S-Ply® leaf springs:


1. S-Ply® leaf springs possess a high elastic energy storage capacity (low modulus), combined with a high mechanical strength. 


Result: In comparison with steel leaf springs they have significantly greater spring action,  higher internal damping and a more balanced springing behaviour, with a many times greater retention capacity of elastic energy than spring steel.


2. The mechanical properties of S-Ply® leaf springs can be adapted for various applications by the orientation to each other of different prepregnated layers.


Result: The overall, available mechanical strength is concentrated exactly where it is needed. This provides ideal tuning of the spring to the load.


3. S-Ply® leaf springs provide a balanced ratio of mechanical strength against weight. Further attributes are high fatigue strength with “fail-safe-characteristics”, corrosion resistance, impact resistance and also electrical insulation.


Result: These characteristics make it possible to construct high performance, mechanical and dynamic systems.