THE EFFECT OF PLY ORIENTATION ON THE PERFORMANCE OF ANTENNAS IN OR ON CARBON FIBER COMPOSITES

In this paper, the anisotropic conductivity effect of quasi-isotropic carbon fiber laminates on conformal load-bearing antenna structures (CLAS) is presented. The conductivity of a quasi-isotropic IM7/977-3 CFRP laminate is measured using waveguide techniques. The results show that orientation of the surface ply relative to the polarization of the incident E-field has a major influence on the reflectivity. This difference is attributed to the fact that carbon fibres oriented parallel to the E-field plies behave as good conductors, while off-axis plies present as lossy dielectric layers with a finite conductivity. This anisotropic behavior of the ply layers is shown to have a distinctive influence on the operation of both microstrip patch and slot antennas.