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- 2015 (12) (entfernen)
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- CFRP (1)
- Crack propagation (1)
- Damage evolution (1)
- Fatigue (1)
- Fractography (1)
- Fracture mechanics (1)
- PA-GF30 (1)
- Pultruded fibre rods (1)
- Spar cap design (1)
- X-ray-refraction (1)
Eingeladener Vortrag
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The following paper focuses on the evolution of micro damage in short fibre reinforced polyamide. Therefore, tube samples are subjected to uni- and biaxial fatigue loadings. The evolution of micro damage is analysed by the non-destructive method of X-ray refraction analysis with consideration of the fibre orientation distribution. For validation of the applied micro damage models, fractographic analyses are performed. Concluding some general results, it has been observed that the load ratio influences the quantitative dominance of micro damage, whereas occurring damage phenomena depend on the type of loading (i.e. tension and torsion). Thus, zones in the Haigh-diagram are detected, where the occurrence of damage mechanisms qualitatively and quantitatively changes. This is a basis for further research regarding anisotropic damage criteria.
The damage process of short glass fibre (30% weight) reinforced polyamide caused by mechanical loading was investigated from the beginning on micro cracking level to the incipient crack of mm-dimension. Based on high resolution computer tomography and the X-ray-refraction technique the inner surface due to micro-cracking at the short fibre ends and the fibre matrix debonding of the skin surface of the filament was determined quantitatively. With the knowledge of the fatigue crack propagation rate and fracture toughness of the material from former research projects, it was derived that the total inner surface due to micro cracks measured by X-ray refraction is much higher than the specimen could have withstand the load, supposed the surface is in a localized crack. Hence, the damage process could be described from micro to macro level. Accompanying fractographic investigations endorse the modelling based on the NDT-techniques.
Fatigue life evaluation of spar cap materials by four point bending test on width-tapered specimens
(2015)
The presented research project focuses on an effective method to evaluate the fatigue strength of thick unidirectional laminates to be applied in spar caps. Therefore, a width-tapered bending specimen was developed for a four point loading set up. Static and fatigue loading was performed with the load ratio of R=-1. The complex stress state was investigated numerically with a finite element analysis. Finally, the concept was proven experimentally on specimens made of pultruded fibre rods. The fatigue behaviour of continuous tapered width by water jet cutting was compared to discrete tapering by rod-drop.