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

除了已建立的短纤维增强热塑性塑料外，具有较长不连续纤维（LFT：长纤维增强热塑性塑料）的热塑性材料的重要性正在不断增加。LFT的微观结构受到各自制造工艺的强烈影响，其特征是局部变化的纤维取向、纤维长度和纤维曲率。当载荷不断增加时，LFT会出现不同的破坏机制，其特征不仅取决于载荷，还取决于微观结构的特征。在文献中，确实有通过模拟单个损伤机制来描述这些复合材料破坏行为的工作，然而，不同平行或先后失效机制之间的区别，特别是基于物理特性的描述是一个具有挑战性且尚未解决的问题。特别是对于LFT，纤维曲率对强度的影响可以说是未知的。计划中的项目旨在填补这一研究空白。IKV的初步研究表明，LFT的材料行为可以使用基于平均场（MF）理论的材料模型以很好的精度表示，并且具有实际的计算时间。损伤行为大多是在微观层面开始的，不能用MF模型来调整。因此，该项目的目的是使用平均场理论对考虑不同纤维长度和纤维曲率的LFT损伤行为进行示例性描述。

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.