University of Twente Student Theses
Test method for measuring electrical resistivity of UD CFRP materials with off-axis fibre orientations : A study towards a better understanding of the electrical behaviour within the complex fibre network of UD CFRP’s
Coulibaly, A.A. (2023) Test method for measuring electrical resistivity of UD CFRP materials with off-axis fibre orientations : A study towards a better understanding of the electrical behaviour within the complex fibre network of UD CFRP’s.
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| Abstract: | Carbon fibre reinforced polymer composites (CFRPs) are showing increased promise in the aerospace industry due to their excellent mechanical properties and low density. Specifically thermoplastic composites are gaining interest because of their melt processability that provides advantages in terms of part manufacturing and assembly. Induction welding is one of the more attractive assembly technologies that utilizes the melt-processability of the thermoplastic matrix. The process utilizes an induction coil to generate eddy currents in the carbon fiber network which, as a result of their resistivity, will heat in order to melt the surrounding matrix material. Although the process is already used in practice, it still relies on time-consuming and expensive trial-and-error procedures to define processing windows. A numerical model capable of predicting the heat generation inside of a CFRP laminate during induction heating would provide significant value and reduce the costs and time associated with process development. One of the challenges towards process simulation is predicting and characterizing the electrical behaviour of the bulk composite material. The aim of the present work is to design a comprehensive test method for measuring the flow of current inside unidirectional (UD) CFRP laminates along directions that are not parallel with the fibres. Numerical modelling is used to simulate, and visualize, electrical phenomena within the composite material with the aim to design the test setup. Six line-contact electrodes are used to run current through specimens, and simultaneously measure voltage differences at the top and bottom surfaces of said specimen. It is found that equipotential lines form parallel to the fibre orientation of UD laminates. Along these lines, the electric potential is constant. As a result of this, line-contact electrodes must be placed parallel to the fibre orientation to avoid short circuits that can influence measurement data. Based on the simulations, the test method is designed, developed, and subsequently employed to characterize three common materials used in the aerospace industry. Significant error is found between the measured values, and the values predicted using analytical expressions. This means that physical measurements are still necessary to determine the off-axis resistivity. Further research into the electrical behaviour of composite materials is necessary to reduce this error; and to ensure that models capable of accurately predicting directional resistivity regardless of fibre orientation can be built. |
| Item Type: | Essay (Master) |
| Clients: | Thermoplastic Composites Research Center (TPRC), Enschede |
| Faculty: | ET: Engineering Technology |
| Subject: | 52 mechanical engineering |
| Programme: | Mechanical Engineering MSc (60439) |
| Link to this item: | https://purl.utwente.nl/essays/95022 |
| Export this item as: | BibTeX EndNote HTML Citation Reference Manager |
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