Janko Kreikemeier

Fatigue damage model for fibre-reinforced polymers at different temperatures considering stress ratio effects:

Most of the existing fatigue models for fibre-reinforced polymers are limited to a specific use case. The investigation presented in this paper provides a progressive fatigue damage model that can be used for fatigue analysis of composite structures under general loading conditions and at arbitrary ambient temperatures. The model is based on an existing approach that already considers mean stress and degradation effects. This model is extended for predicting fatigue damage at general loading conditions. To incorporate the effect of ambient temperatures, material and model parameters are defined temperature dependent. The new model is validated using two composite materials and different loading conditions as well as under both room and high temperatures. The model achieves a good prediction quality for the analysed materials, loading conditions and temperatures. This demonstrates that the proposed model is not limited to a specific use case but is able to simulate fatigue of laminated composites under general loading conditions.

Modeling of Manufacturing Uncertainties by Multiscale Approaches

In this chapter, a numerical multiscale modeling approach is presented and discussed. It bases on the FE² approach in which a simultaneous finite element computation of the mechanical response at two different length scales is carried out at each macroscopic integration point. The approach is suitable to obtain the global load response of composite structures without omitting the effect of physical phenomena at the local scale, as for example process-induced defects like voids or fiber waviness.