Due to the increasing application of carbon fibre–reinforced plastics, the use of recycled carbon fibres can help reduce the tremendous amount of carbon fibre waste growing worldwide. In this context, the processing of longer recycled carbon fibres (>40 mm mean length) into hybrid yarn constructions offers a promising solution. The characterisation of recycled carbon fibre length is essential for textile processes. However, to suit the atypical fibre characteristics of recycled carbon fibres compared to standard natural or man-made-fibres, the development of an adequate measuring technique is required. Investigations on the state of the art suggest that an adapted fibrograph method might pose an appropriate measuring system. Therefore, new test equipment and an alternative image analysing method based on pixel greyscale values were developed. To enable a calibration process, different samples with cut carbon fibre from carded and drafted slivers were intensively tested and compared. In addition, an adapted reference method was investigated by combining single fibre measurement and image processing techniques. In a final step, recycled carbon fibres samples with unknown fibre length were tested. Results proved that the presented measuring system is adequate for the testing of longer recycled carbon fibres in webs or slivers. All measured values were close to the measured reference length values (deviation ±4%).

中文翻译：

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用于高性能复合材料的再生碳纤维新型混合纱线结构的开发：第四部分：再生碳纤维长度的测量

由于碳纤维增强塑料的应用越来越多，再生碳纤维的使用有助于减少世界范围内大量增长的碳纤维废物。在这种情况下，将较长的回收碳纤维（平均长度 > 40 毫米）加工成混合纱线结构提供了一个有前景的解决方案。再生碳纤维长度的表征对于纺织工艺至关重要。然而，为了适应再生碳纤维与标准天然或人造纤维相比的非典型纤维特性，需要开发适当的测量技术。对现有技术的调查表明，经过调整的纤维成像方法可能会构成合适的测量系统。因此，开发了新的测试设备和基于像素灰度值的替代图像分析方法。为了能够进行校准过程，对不同的样品进行了深入测试和比较，这些样品具有从梳理和牵伸的条子上切割下来的碳纤维。此外，通过结合单纤维测量和图像处理技术，研究了一种适应性参考方法。在最后一步，测试了纤维长度未知的回收碳纤维样品。结果证明，所提出的测量系统足以测试纤维网或条子中较长的回收碳纤维。所有测量值都接近测量的参考长度值（偏差±4%）。在最后一步，测试了纤维长度未知的回收碳纤维样品。结果证明，所提出的测量系统足以测试纤维网或条子中较长的回收碳纤维。所有测量值都接近测量的参考长度值（偏差±4%）。在最后一步，测试了纤维长度未知的回收碳纤维样品。结果证明，所提出的测量系统足以测试纤维网或条子中较长的回收碳纤维。所有测量值都接近测量的参考长度值（偏差±4%）。