For the reliable and cost-efficient application of glass fibre polymer composites in structural applications, knowledge of the damage state of the material during operation is necessary. Within this work, a structural health monitoring method based on in-situ electrical capacitance measurements is presented, which enables damage monitoring in glass fibre reinforced polymers. For this purpose, individual glass fibre rovings in a non-crimp fabric were replaced by carbon fibre rovings at regular intervals. Additionally, specimens with solid or stranded copper conductors were manufactured to gain insights into the influences of conductor material and composition. The modified fabrics were implemented as 90∘ layers of [0/904]s glass fibre polymer cross-ply laminates. To monitor the progressive damage, conductive rovings were contacted, forming the capacitor walls of interleaved capacitors. Carbon fibre conductors show higher sensitivity of the capacitance to crack formation than solid or stranded copper conductors. Capacitance decrease measured in-situ during tensile tests on specimens with carbon fibre conductors shows a high correlation with crack initiation, further crack formation and speed of crack evolution. An analytical model can describe the correlation based on the assumptions of an ideal plate capacitor. Thus, the structural health monitoring method developed in this work can reveal in-situ knowledge of the material damage state.

中文翻译：

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用于检测GFRP中基体裂纹的集成导体的电容测量

为了将玻璃纤维聚合物复合材料可靠且经济地应用于结构应用中，必须了解操作过程中材料的损坏状态。在这项工作中，提出了一种基于原位电容测量的结构健康监测方法，该方法可以监测玻璃纤维增​​强聚合物中的损伤。为此，将非卷曲织物中的单个玻璃纤维粗纱定期更换为碳纤维粗纱。此外，还制作了带有实心或绞合铜导体的样品，以深入了解导体材料和成分的影响。改性织物被制成90层[0/904] s玻璃纤维聚合物交叉层压材料。为了监控渐进式损坏，接触了导电粗纱，形成交错电容器的电容器壁。与实心或绞合铜导体相比，碳纤维导体对电容形成裂纹的敏感性更高。在具有碳纤维导体的试样上进行拉伸试验时，原位测量的电容降低与裂纹萌生，进一步的裂纹形成和裂纹发展速度高度相关。分析模型可以基于理想平板电容器的假设来描述相关性。因此，这项工作中开发的结构健康监测方法可以揭示材料损坏状态的现场知识。在具有碳纤维导体的试样上进行拉伸试验时，原位测量的电容降低与裂纹萌生，进一步的裂纹形成和裂纹发展速度高度相关。分析模型可以基于理想平板电容器的假设来描述相关性。因此，这项工作中开发的结构健康监测方法可以揭示材料损坏状态的现场知识。在具有碳纤维导体的试样上进行拉伸试验时，原位测量的电容降低与裂纹萌生，进一步的裂纹形成和裂纹发展速度高度相关。分析模型可以基于理想平板电容器的假设来描述相关性。因此，这项工作中开发的结构健康监测方法可以揭示材料损坏状态的现场知识。