Structural health monitoring based on detecting strain enables further exploitation of the lightweight potential of aircraft structures. Since carbon fibres (CF) can be easily integrated into aircraft structures made of fibre-reinforced plastics (FRP), their use in sensor applications has become subject of research. One of many novel approaches is the use of cracked CF for strain detection. During loading and unloading, the fibre cracks are opening and closing respectively, resulting in substantial changes in the electric resistance of the CF. The high dependence of the electric resistance on the mechanical strain enables spatially resolved strain sensing along the CF based on the electric time domain reflectometry (ETDR) principle. However, due to high inhomogeneity of the used pitch-based CF and the resulting electric properties, the ETDR-signal is degraded largely by impedance mismatch along the transmission line, which limits the measuring length of a spatially resolved sensor. In this contribution, a concept for a spatially resolved CF-based strain sensor is described, outlining the challenges that need to be addressed. One approach for the extension of the measuring length is lowering the base resistivity of the used CF, which is discussed in detail. In order to achieve a low base resistivity while maintaining the characteristic of opening and closing fibre cracks, copper-coated CF are investigated. The copper-coated pitch-based CF are integrated into test specimens consisting of a composite material and are subjected to tensile loading. Simultaneously to the deflection, the electrical resistance is measured. Consequently, the sensitivity to strain of the CF is determined and discussed.
|Journal of Physics: Conference Series
|Veröffentlicht - 28 Juni 2023
|12th EASN International Conference on "Innovation in Aviation & Space for opening New Horizons"
|18 - 21 Oktober 2022
|Universitat Politècnica de Catalunya