Electrical Resistivity and Microwave Properties of Carbon Fiber Felt Composites

We present studies on the microwave properties, electrical resistivity, and low-frequency (10 Hz-20 kHz) noise characteristics in the temperature range of 78 K to 380 K of composite materials made from bisphenol A-based epoxy resin and carbon fiber felts. Two types of carbon fibers were used, derived from polyacrylonitrile or regenerated cellulose. We show that these structures are suitable for electromagnetic shielding applications, especially in the direction parallel to the carbon fibers. The low-frequency voltage fluctuations observed in these materials are of the 1/f(alpha), and the noise intensity is proportional to the square of the voltage. The characteristics of the investigated materials show an instability in the temperature range from 307 K to 332 K. This effect is followed by an increase in resistivity and noise intensity, but it does not change the character of the noise, and this instability vanishes after a few repeated heating and cooling cycles.

Automated summary

Studies on composite materials made from bisphenol A-based epoxy resin and carbon fiber felts show stable microwave properties and resistivity in a specific temperature range, suitable for electromagnetic shielding applications. The observed low-frequency voltage fluctuations in the materials follow a 1/f(alpha) characteristic, with an instability in the temperature range of 307 K to 332 K. This instability is accompanied by an increase in resistivity and noise intensity, but does not change the nature of the noise, and disappears after repeated heating and cooling cycles.