Damage of fibre reinforced plastics caused by the inner multiaxial stress state owing to thermal, hygrothermal and multiaxial mechanical loads

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It is a general hypothesis of this research proposal that the fatigue behavior of fibre reinforced plastics (FRP) is exclusively influenced by local stresses within the individual layers of the composite. Although these local stresses may have different causes, such as mechanical loads or a change in temperature and humidity, the effect - fatigue - still is comparable. It is therefore assumed, that the cause of local stresses does not influence their effect. The project is to investigate the behavior of FRPs exposed to mechanical, thermal and hygrothermal loads. In accordance with the research hypothesis an extensive and well-tuned experimental program shall be conducted. All experiments focus on understanding gradual damaging of FRPs, which will be resolved on a microscale using adequate measuring systems. Different inner local stress states are reproduced by specific control and combination of outer loads (multiaxially mechanical, thermal, hygrothermal) and by the use of various laminates, which differ in stacking sequence and layer thickness. All laminates are strictly divided in layers of interest and purely supporting layers. Complementary to the experiments, analytical and numerical calculations will determine stress redistribution within the material. Due to the project s extent two collaborating institutes are mandatory.