Effect of carbon black on improving thermal stability, flame retardancy and electrical conductivity of polypropylene/carbon fiber composites

The microwave absorbing properties of multi-layer carbon/carbon fiber composites, designed to function as radar absorbing structures (RAS), were studied over the X-band frequency range (8.0-12.4 GHz). High-frequency electromagnetic properties of various fibers (glass, carbon) and particulate filler (carbon black) are investigated as the major constituent materials of the RAS. Free space measurement depicts the perfect reflecting properties of carbon fiber composites (S11 = 0 dB, S21 = −40 dB). In the two-layered composite laminate (impedance transformer/reflecting substrate), the use of carbon black is necessary in the impedance transforming layer to obtain the high level of microwave absorbance and frequency tuning. Through the layer combination of the glass-fiber composite (thickness = 2.45 mm) containing carbon black (3% in weight) and carbon fiber composite as reflecting substrate, S11 can be reduced to as low as −40 dB at the frequency of 11.7 GHz, maintaining a low level of S21. The results demonstrate that RAS can be efficiently designed with the laminates of fiber reinforced composites with impedance transforming layer (glass fiber with suitable amount of carbon black) and perfectly reflecting substrate (carbon fiber).

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Comparison of Hollow-Porous and Solid Carbon Fibers as Microwave Absorbents

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.150-151.1336 ◽

2010 ◽

Vol 150-151 ◽

pp. 1336-1342 ◽

Cited By ~ 2

Author(s):

Wei Xie ◽

Hai Feng Cheng ◽

Zeng Yong Chu ◽

Zhao Hui Chen ◽

Yong Jiang Zhou ◽

...

Keyword(s):

Electrical Conductivity ◽

Carbon Fiber ◽

Carbon Fibers ◽

Porous Carbon ◽

Fiber Composites ◽

Carbon Fiber Composites ◽

Solid Carbon ◽

Microwave Absorbing Properties ◽

Surface Electrical Conductivity ◽

Microwave Absorbing

A series of polyacrylonitrile-based hollow-porous and solid carbon fibers were prepared by pyrolysis of polyacrylonitrile-based hollow-porous and solid fibers at the same condition. The microstructure, composition, surface electrical conductivity, electromagnetic parameters and reflectivity of carbon fibers were studied. The microwave absorbing properties of two kinds of carbon fibers as microwave absorbents were parallel investigated. Results show that the apparent density of the hollow-porous carbon fibers is lower than that of the solid carbon fibers due to their hollow-porous structure. The surface electrical conductivity of single solid carbon fiber is nearly 10 times that of the hollow-porous carbon fiber. The -10dB bandwidths of solid carbon fiber composites carbonized at 850 and 950°C are both 0GHz, while those of the corresponding hollow-porous carbon fiber composites are up to 3.05 and 2.62GHz, respectively. Results indicate that the microwave absorbing properties of the hollow-porous carbon fiber composites are better than those of solid carbon fiber composites.

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