Experimental and numerical investigation of the damage behaviour of single fibre composites

该项目研究纤维增强塑料的损坏。因此，均质化的概念被部署，跨越三个尺度-微观，中观和宏观。在该项目的第一阶段，开发了在微观尺度上确定纤维和纤维基质界面特性的方法。为了验证这些性能，使用了单纤维断裂试验（SFFT）和拔出试验的模拟和实验结果的比较。在第二阶段，通过与实验的比较，对损伤基体的速率依赖行为进行建模和参数化。因此，复合材料的所有成分的行为被识别。基于这一知识的损伤复合材料的宏观尺度上的有效行为将被确定通过一个两阶段的计算均匀化。这种均匀化包括模拟纤维的代表性随机分布及其微观强度，以及由粗纱组成的中尺度增强结构。所有模拟都将与实验进行比较，以校准部署模型的参数或验证其预测。除上述实验外，还将采用少量纤维的模型复合材料来验证微观尺度上界面和基体损伤的相互作用。均匀化的结果将通过单向和多轴增强试件的实验进行验证。示例性地部署E玻璃和环氧树脂的材料组合以及增强件的纤维几何形状。然而，这些结果对纤维增强塑料的应用具有直接意义。与钢或铝等材料相比，由于缺乏对其损坏行为的量化，它们的潜力开发得很差。

The project investigates the damage of fibre-reinforced plastics. Therefor the concept of homogenisation is deployed, spanning three scales - micro, meso and macro. The methology to determine the properties of the fibres and the fibre-matrix-interface on the microscale was developed during the first period of the project. To characterise those properties, the comparison of simulations and experimental results of single fibre fragmentation tests (SFFT) and pullout test was used. Furthermore the viscoelastic properties of the matrix material were identified.During the second stage the rate dependend behaviour of the damaged matrix shall be modelled and parameterised by comparison with experiments. Thereby the behaviour of all constituents of the composite is identified. Based on this knowledge the effective behaviour of damaged composites on the macroscale will be determined by means of a two-stage computational homogenisation. This homogenisation includes the simulation of representative stochastic distributions of fibres and their strength on the microscale as well as the reinforcement structure consisting of rovings on the mesoscale.All simulations will be compared to experiments to calibrate parameters of the deployed models or to validate their predictions. Besides the mentioned experiments model composites with few fibres will be used to validate the interaction of interface and matrix damage on the microscale. Results of the homogenisation will be validated by experiments on unidirectional and multiaxial reinforced specimen.The proposed investigation is fundamental. Exemplary the material combination of E-glass and epoxy resin as well as the fibre geometry of the reinforcement are deployed. Nevertheless the results are of direct significance in the application of fibre-reinforced plastics. In comparison to materials like steel or aluminium their potential is exploited poorly due to a lack of quantification of their damage behaviour.