Characterisation of electromagnetic properties of carbon fibre composite materials

A method for characterising the electromagnetic properties of woven carbon fibre composite (CFC) materials at HF was investigated. The method made use of two loop antennas and a vector network analyser (VNA) to measure the scattering parameters (S₂₁) of varying layers of carbon fibre. Computational electromagnetic (CEM) modelling of the experimental setup together with a DC surface resistance approximation was then used to match the electromagnetic behaviour. This was achieved by calculating S₂₁ for a range of surface resistance values. A fit between the measured and modelled S₂₁ curves was used to identify the most representative DC surface resistance value for a particular CFC construction which could then be used in models of larger structures. The method showed utility for CFC samples of 2 and 4 layers. However, a 6 layer case demonstrated the technique's limitation at frequencies approaching 30 MHz.