Investigation of the RF Properties of Carbon Fibre Composite Materials

摘要

The resistivity of small CFC samples at frequencies up to 300 MHz was measured using Q-meter techniques. Values of 0.00003 to 0.00015 ohm-meter are typical at low frequencies and increase with increasing frequency indicating the presence of skin effect. Samples showed little change in their d.c. resistance as a result of prolonged exposure to various liquids although boiling in tap or sea water produced substantial increases in resistance. Screening effectiveness to magnetic fields in the range 0.15 - 30 MHz and electric fields in the range 30 - 1000 MHz was measured for panels of CFC incorporated as one face of a copper cubic enclosure and as one surface panel of a Wessex helicopter tail cone. Screening effectiveness of a cylinder completely fabricated from CFC was also measured. Results indicate that the screening effectiveness of a CFC or part CFC fuselage, particularly in the hf band, will be critically dependent on the electrical continuity of bonds and joints and may be significantly less than for present day metal airframes. At vhf and uhf the screening effectiveness of part CFC and present day metal airframes are similar. The performances of vhf and uhf aerials when mounted on CFC or metal ground planes were similar and essentially within manufacturers' specifications.