The objective of this thesis was the characterisation of the fatigue behaviour for discontinuous shortglass fiber reinforced (sgfr) polymers under cyclic tension and compression loading. Two different types of composites were tested. This was on one hand a thermoset, a type of polyphtalamide and on the other hand a phenol-formaldehyderesin.
Different types of test specimen were tested under sinusoidal load control at a temperature of 23 °C, different frequencies and R ratios of 0,1 and 10. The cycle limit for the testing was defined with 10 6 [hoch 6] cycles.
Because of the different production technologies of the specimens, the differences in the structure were investigated.
The test methods applied considered considering two different aspects.
The first one was to characterize the fatigue behaviour before failure using so-called isocyclic stress-strain diagrams. The second one was to characterize the fatigue behaviour at failure with the Wöhler-curves and the description of the fatigue crack growth resistance with the linear elastic fracture mechanics approach (crack growth-curves). Finally the correlation between the results from the Wöhler-curves and from the linear elastic fracture mechanics approach should be compared by using a transformation concept.
The monotonic tensile and compression behaviour was also characterized.
With the isocyclic stress-strain-diagrams it could be shown that the fatigue behaviour is basically dominated by visco-elastic-effects. The Wöhler-curves show striking differences depending on the type of specimen. The fatigue
crack growth was analysed for the selected materials. In addition to that pictures with a scanning electron microscope provided some information on failure effects. The correlation between the Wöhler-curves and the crack growth-curves showed a deviation, at least in the first approach.