Quantitative correlation of micro- and macromechanical parameters of endless fibre reinforced plastics

单向连续纤维增强塑料（UD-FRP）具有高的重量比强度和刚度，以及良好的能量吸收能力和纤维平行拉伸载荷下的疲劳行为。因此，了解FRP在纤维平行拉伸载荷下的性能是非常重要的。然而，由于微机械异质结构，复合材料性能的考虑比金属材料更复杂，需要对损伤行为和潜在机制有更深入的了解。根据文献，具有热固性基质的碳纤维或玻璃纤维增强材料存在基本的损坏机制，例如纤维断裂、纤维脱粘和基质损坏。因此，这些机制之间存在复杂的相互作用。在静态、碰撞相关和循环载荷情况下，这些微机械机制受到纤维和基质类型以及纤维/基质界面性质的不同影响，因此对于这些载荷情况及其要求存在最佳纤维/基质组合。虽然在文献中有个别机制和影响因素的调查，没有研究的所有基本因素的相互作用与统一的边界条件可以找到。因此，它是不完全理解的组成属性如何影响损伤和宏观力学参数，如拉伸强度和疲劳寿命。各种细观力学模型已被开发来研究这一主题，沿着三维剪切滞后模型（SLM）提供了最大的潜力。该项目的目的是进一步开发UD-FRP在不同荷载情况下（准静态荷载和疲劳）的剪切-滞后模型，并评估该模型对不同纤维/基体组合的适用性。进一步的目标是通过模拟预测力学参数，以便通过材料选择优化UD-FRP的性能。为了实现这一目标，将进一步开发这些荷载情况下的剪滞模型。同时，微观力学输入参数的模型和不同的纤维/基体组合的宏观力学参数将实验表征。然后将分析模型的预测质量，以评估模型适用于哪些纤维/基质组合和哪些负载情况。作为应用项目的直接结果，将开发用于预测力学参数的验证模型。此外，将扩展对影响因素之间的相互作用的理解。

Unidirectional continuous fibre-reinforced plastics (UD-FRP) have high weight-specific strength and stiffness as well as good energy absorption capacity and fatigue behaviour under fibre-parallel tensile load. For this reason, understanding the properties of FRP under fibre-parallel tensile load is of great importance. Due to the micromechanically heterogeneous structure, however, the consideration of composite properties is more complex than with metal materials and requires a deeper understanding of the damage behaviour and the underlying mechanisms. According to the literature, there are essential damage mechanisms for carbon fibre or glass fibre reinforcement with a thermoset matrix, e.g. fibre breakage, fibre debonding and matrix damage. Therefore, there are complex interactions between the mechanisms. In static, crash-relevant, and cyclic load cases, these micromechanical mechanisms are influenced differently by the fibre and matrix types and the properties of the fibre/matrix-interface, so that there is an optimum fibre/matrix combination for these load cases and their requirements. Although in the literature there are investigations on individual mechanisms and influencing factors, no studies on the interaction of all essential factors with uniform boundary conditions can be found. It is therefore not fully understood how the constituent properties influence the damage and the macro-mechanical parameters, such as tensile strength, and fatigue life. Various micromechanical models have been developed to investigate this topic, along with the three-dimensional Shear-Lag model (SLM) offers the greatest potential. The aim of this project is the further development of the Shear-Lag model for UD-FRP for different load cases (quasi-static load and fatigue) and the evaluation of the applicability of the model for different fibre/matrix combinations. A further goal is the prediction of the mechanical parameters by simulation so that the performance of UD-FRP can be optimized application-specifically by material selection.To achieve this goal, the shear-lag model will be further developed for these load cases. At the same time, the micro-mechanical input parameters of the model and the macro-mechanical parameters of different fibre/matrix combinations will be characterized experimentally. The predictive quality of the model will then be analysed to evaluate for which fibre/matrix combinations and which load cases the model is suitable. As a direct result of the applied project, a validated model for the prediction of the mechanical parameters will be developed. Furthermore, the understanding of the interaction between the influencing factors will be extended.