Influence of CVI treatment of carbon fibers on the electromagnetic interference of CFRC composites

Short carbon fibers were,treated at temperatures around 1100 degrees C in a furnace through chemical vapor infiltration technology. The fiber surface was observed by scanning electron microscopy. The reflectivity of electromagnetic radiation by the composites that were reinforced by surface-treated carbon fibers and by as-received ones was measured in the frequency range of 8.0-18.0 GHz. The reflectivity for different carbon fiber contents of 0.2%, 0.4%, 0.6% and 1.0 wt% was investigated. Results showed that the reflectivity of the composites that were reinforced by untreated carbon fibers tended to increase with the increasing fiber contents. The minimum reflectivity was -19.3 dB, far less than -10 dB, when the fiber content was 0.4% and there were wave-absorbing properties. However, after surface treatment, the minimum reflectivity was -8.1 dB for the same fiber content of 0.4%, indicating significant wave-reflecting properties. The achieved reflectivity values after surface treatment were generally greater than those without treatment. (C) 2007 Elsevier Ltd. All rights reserved.