Analysis and modeling of the damage behavior of long-fibre-reinforced semi-crystalline thermoplastics considering fibre length and fibre curvature

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In addition to the established short-fibre reinforced thermoplastics, the importance of thermoplastic materials with longer discontinuous fibres (LFT: long fibre reinforced thermoplastics) is continuously increasing. The microstructure of LFT is strongly influenced by the respective manufacturing process and is characterised by locally varying fibre orientations, fibre lengths and fibre curvature.If an LFT is loaded increasingly, there are different failure mechanisms whose characteristics depend each on the load, but also on the characteristics of the microstructure. In the literature, there are indeed works that describe the failure behaviour of these composites by modelling individual damage mechanisms, however, the distinction between different parallel or successively expiring mechanisms and in particular, the description on the basis of physical characteristics is a challenging and yet unsolved problem. Especially for LFT, the influence of fibre curvature on the strength can be called unexplored.The planned project aims in this research gap. Preliminary investigations at IKV have shown that the material behaviour of LFT can be represented in good accuracy using material models based on the mean-field (MF) theory with practicable calculation times. The damage behaviour, which is mostly initiated at the micro level, cannot be adjusted using the MF models. The aim of the project is therefore the exemplary description of the damage behaviour of LFT considering different fibre lengths and fibre curvatures using the mean-field theory.