Abstract
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%).
Highlights
A fibre length measurement system of long recycled carbon fibres (rCF) in webs and slivers for subsequent yarn spinning based on an adapted fibrograph method was presented
According to the state of the art, it is estimated that this fibrograph method, measuring non-end-aligned fibre beard samples, is an appropriate and fast testing principle for the measuring of long rCF due to their specific fibre characteristics
A self-built clamp was used and a conventional flatbed scanner was modified for the testing of fibre beards that consist of long rCF
Summary
In order to calibrate the fibrograph method, information on the fibre length of CF and rCF prior to and after textile processing within a reference method is required This developed reference method is a combination of measuring the length of CF or rCF fibre bundles with a single fibre measuring method and calculating the number of fibres per bundle based on scanning and image processing. Each bundle was scanned (scanning parameters identical with the adapted fibrograph method), and the resulting images were processed with the ImageJ software,[31] where the pixel value sum for each bundle was calculated and divided by the bundle pixel length Based on this calculation, the relationship between the average pixel value sum of bundles and the known number of fibres in bundles was established and summarised as bundle factor. The references MLR, UHMLR and UIR were calculated
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