Abstract
Electrical Impedance Measurement has been used to measure the diameter of single carbon fibres to within 3% of the actual value measured by Scanning Electron Microscopy (SEM). The precision of the technique developed also allows for the accurate determination of the number of fibres present in a carbon fibre bundle, such data are important for the calculation of fibre tensile strength from the tensile force applied to carbon fibre bundles. The impedance of a single carbon fibre and carbon fibre bundles of up to 20 fibres have been measured, with results showing good agreement with theoretical values. The impedance of multiple lengths of carbon fibres ranging from 80 to 300mm has also been studied, with the impedance being directly proportional to the fibre length, as per electrical theory. This technique will be suitable for determining the number of fibres in a virgin or recycled carbon fibre bundle.
Highlights
The tensile strength of carbon fibre is an important parameter when considering the application of the final composite product
For low impedance measurements this value should be subtracted from the impedance measured
The single fibre diameters calculated from Electrical Impedance Measurement (EIM) and measured by Scanning electron microscopy (SEM) are presented in Table 2 for different fibre lengths
Summary
The tensile strength of carbon fibre is an important parameter when considering the application of the final composite product. Calculation of the cross-sectional area of a single carbon fibre is trivial, the cross-sectional area of a bundle of fibres is difficult to determine. This difficulty arises from the uncertainty in the number of fibres within the bundle. Fundamental to the use of EIS is the generation of an equivalent circuit, a process by which a physical system is modelled by a set of electrical components. In doing so the tensile strength of recycled fibres may be calculated and potentially used as a means of classification
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