The efficient solution of this problem is possible with the help of polarization-interferential method. In this case unilayered carbon fiber based material could be described by a model of a homogeneous dielectric layer of binder on one side of which a polarization grid made from parallel conducting wires is located.

The method consists in irradiation of tested material by a linearly polarized electromagnetic wave of microwave range, with the polarization plane oriented at an angle of 45° to the direction of carbon fibers. Taking into consideration the peculiarities of interaction between the probing electromagnetic wave and the grid, one should take the transmitted and reflected wave as resulted from the interaction. Then their polarization plane and direction are converted by 90° and 180° respectively, and the tested material is irradiated once again. At a final step, both waves are received and summed up. The mixing of doubly interacted wave components in one channel leads to a formation of elliptically polarized electromagnetic wave with the ellipticity being depended on phase difference of the orthogonally polarized components and the azimuth-by relationship of their amplitudes. The phase shift between the components for the given type of composite material depends on the quality and thickness of a binder, while the amplitude relationship depends mainly on the angle between the polarization plane of probing wave and direction of carbon fibers.

The present method has been implemented in the microwave device for simultaneous testing of binder volume and direction of reinforcing fibers with an error not exceeded 3%.