Impact of the statistical scatter of the complex permittivity of carbon nanotube composite sheets on Salisbury-screen-type radar absorbing structures

This study presents simple statistics based on the normal distribution of the measured complex permittivity of carbon nanocomposite sheets and an analytical approach to estimate its impact on the radar absorbing performance of the Salisbury-screen-type radar absorbing structure of the composite sheet. The composite sheets are fabricated with glass fabric/epoxy prepregs containing dispersed carbon nanotubes. The complex permittivity is measured with a free-space measurement system equipped with horn antennas with focal lenses and a vector network analyzer. The radar absorbing structure designed at a target frequency of 10 GHz has a peak reflection loss at -45 dB, which is obtained on the basis of the average complex permittivity of the composite sheet. The lowest reflection losses are calculated for confidence intervals of 95% and 99% of the normal distribution of the complex permittivity of the composite sheets, which are -34 dB and -31 dB, respectively.