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

该项目调查纤维增强塑料的损坏情况。为此，运用了均质化的概念，跨越了三个尺度--微观、中观和宏观。在该项目的第一阶段，发展了在微观尺度上确定纤维和纤维-基质-界面的性质的方法。为了表征这些特性，采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。此外，还识别了基质材料的粘弹性性质。在第二阶段中，应通过与实验的比较来模拟和参数化受损基质的速率依赖行为。从而确定了该组合物的所有组分的行为。基于这些知识，损伤复合材料在宏观尺度上的有效行为将通过两个阶段的计算均化来确定。这种均化包括在微观尺度上模拟典型的纤维及其强度的随机分布，以及在介观尺度上模拟由粗纱组成的增强结构。所有模拟都将与实验进行比较，以校准展开的模型的参数或验证它们的预测。此外，还将利用少量纤维的模型复合材料在微观尺度上验证界面和基质损伤的相互作用。均质化的结果将通过单向和多轴增强试件的实验来验证。建议的研究是基础。示例性的E玻璃和环氧树脂的材料组合以及增强的纤维几何形状被展开。研究结果对纤维增强塑料的应用具有直接的指导意义。与钢铁或铝等材料相比，由于缺乏对其破坏行为的量化，它们的潜力被开发得很差。

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.