The chemical precipitation was used to obtain carbon fibers (CF) with surface modified by magnetite particles (Fe₃O₄). Processing was carried out by employing up to three subsequent coating stages of ultrasonic treatments. After each sonication stage, the coating was 17, 33, and 47 wt. % of the total weight of the modified fibers. Raman spectroscopy indicates the presence in the coating of a mixture of iron II and III states. As-decorated fibers were used to fabricate composites with an epoxy resin (ED-20) matrix cured with PEPA. The quantity of the carbon fiber filler was of 1, 3, and 6 wt %. At room temperature, the saturation magnetization of the soft magnetic samples was 0.37, 0.83, and 1.72 emu/g for the indicated compositions. Carbon fiber reinforced polymer materials with extra functions such as magnetic in this case, are expected to be useful in applications from the power and energy industries.

With the rapid development of wireless communication technologies and the miniaturization trend in the electronics industry, the reduction of electromagnetic interference has become an important issue. To solve this problem, a lot of attention has been focused on polymer composites with combined functional fillers. In this paper, we report a method for creating an acrylonitrile butadiene styrene (ABS) plastic composite with a low amount of conductive carbon and magnetic fillers preparation. Also, we investigate the mechanical, thermophysical, and electrodynamic characteristics of the resulting composites. Increasing the combined filler amount in the ABS composite from 1 to 5 wt % leads to a composite conductivity growth of almost 50 times. It is necessary to underline the temperature decrease of 5 wt % mass loss and, accordingly, the composite heat resistance reduction with an increase in the combined filler from 1 to 5 wt %, while the thermal conductivity remains almost constant. It was established that electrodynamic and physical–mechanical characteristics depend on the agglomeration of fillers. This work is expected to reveal the potential of combining commercially available fillers to construct effective materials with good electromagnetic interference (EMI) protection using mass production methods (extrusion and injection molding).