Effects of Advanced Composites on Shielding and Antenna Performance

The shielding effectiveness of composite panels is examined for a plane wave source representative of an electromagnetic (EM) interference threat for the frequency range of 50 kHz to 18 GHz. The effects of fabrication details are demonstrated by test data from three structures which used different panel thicknesses and methods of panel attachment. An assessment of the inherent shielding of composite material is made by analysis and from the results of tests on specimens subjected to a TEM wave in a coaxial line. Results show that while the shielding provided by composite materials is much less than for metal, it is large enough that in most cases the leakage through joints or seams will be the limiting factor in the shielding effectiveness of structures. equal unless the wave impedance (E to H ratio) is a constant value (independent of position) on both sides of the shield. This emphasizes the fact that measured values for shielding effectiveness are not unique to the material being tested but depend upon the test configuration and procedures employed.