Enhanced microwave shielding effectiveness and suppressed reflection of chopped carbon fiber felt by electrostatic flocking of carbon fiber

Abstract This work fabricated absorption-dominated and low reflection microwave shielding material in X band (8.2-12.4 GHz). Short chopped carbon fibers (CFs) were aligned vertically on short chopped CF felt with the help of electrostatic flocking technique, and epoxy resin was chosen as matrix to support such structure. Vertical alignment of chopped CFs efficiently reduces surficial reflection to let microwave penetrate and be dissipated inside the shielding structure of CF. Pitch-based CFs with different length were flocked on polyacrylonitrile-based CF felt with different flocking density. It showed that after 28.5 g/m2 of 8 mm CFs being flocked on CF felt, the average reflection (0.4 dB) decreases by 95% compared to CF felt, while the average shielding effectiveness (32.3 dB) and absorption (31.9 dB) increase by 25% and 85% respectively. Such improvement is attributed to multi-cooperated shielding mechanism, in which internal multi-reflection among flocking CFs and quarter-wavelength attenuation play essential roles.