Effect of the planar coil and linear arrangements of continuous carbon fiber tow on the electromagnetic interference shielding effectiveness, with comparison of carbon fibers with and without nickel coating

The effect of macroscale planar arrangement (planar coil, unidirectional and crossply arrangements, with a gap between tow segments) of continuous polyacrylonitrile-based carbon fiber (7.0-μm diameter) 12 K tow on the electromagnetic interference shielding effectiveness for normal-incident unpolarized plane wave is reported at frequencies ranging from 200 to 2000 MHz. The planar coil configuration, which favors magnetic interaction, has not been previously reported for shielding with any material. For all arrangements, the total shielding effectiveness (SE_T) is dominated by the absorption loss (SE_A), whether the fiber is nickel-coated or not. The nickel coating (0.25-μm thick) increases SE_T from 2‒6 dB to 13–26 dB for the planar coil configuration, but has little effect for the crossply/unidirectional configuration. Both SE_T and SE_A are greatly increased by the nickel coating, which also reduces SE_A's frequency dependence and increases the absorption's fractional contribution to shielding, particularly for the planar coil configuration below 1000 MHz (from 53%‒78% to 83%–94%). The advantage of the crossply configuration over the unidirectional configuration is greater without the nickel coating. Increasing the tow size from 12 K to 24 K (with the gap decreased from 3.0 to 2.0 mm) raises SE_A for planar coil and unidirectional arrangements. The results agree essentially with electromagnetic theory.