Research on methods to reduce the scattering and to increase the fatigue life of unidirectional fibre-polymer-composites

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A main focus of composite research concentrates on the failure behaviour of this material group. Especially structures which are fatigue loaded for long term are of great interest, e.g. leaf springs for trucks. Glass fibres succeeded in the recent years as the most suitable material for leaf springs. The big advantage of glass fibres for this case is their low Young's modulus, by which the requirement of high bending deformation can be fulfilled the most easiest. Leaf springs for the Daimler Sprinter are manufactured in large series since 2006. It must be the aim, to introduce the GRP-leaf springs especially for heavy trucks. By substituting steel springs a weight saving of about 75% of the spring mass is achievable, that means a weight reduction of 130 kg at the rear axle of the truck. This mass saving can be used for increasing the pay load and to lower the CO2 emission. In future an increase of the market share of the GRP leaf spring can be expected, that means a stronger competition to steel.To keep competetive with the GRP leaf spring it is absolutely necessary to scoop out all the potential of the material. To reach this goal a lot of fundamentals have to be worked out; this concerns- the non economic safety factors, which are used at this time for the design of these components- the calculation of the fatigue life- all chances to increase the life time.The sketched aim can be reached by lowering the scattering of strength of the leaf spring laminates and by testing new concepts to increase fatigue life.