Poly(vinylidene fluoride) (PVDF) based composites loaded with 3 wt% of carbon black (CB), graphite (GF), and the hybrid CB/GF (1.5/1.5 wt%) were prepared by melt mixing and tested as microwave absorbing material at X-band frequencies (8-12 GHz). The materials were processed and pressed at 220 C into plates of 20 × 20 × 0.1 cm 3. Dielectric and magnetic properties were evaluated using the wave-guide accessory to simulate the reflectivity of singlelayered PVDF composites through impedance matching behavior. The best absorbing properties were achieved with the composite loaded with the CB/GF hybrid material, whose maximum of radiation attenuation of −33 dB at 9.3 GHz was predicted with 4 mm thickness. Afterwards, the reflectivity of sandwiched structures (20 × 20 cm 2 in size) with one-layer honeycomb core sandwiched by two plates of PVDF composites was measured. The PVDF/HBhoneycomb-PVDF/HB structure reached reflection loss = −12 dB (E a = 94%) on a broadband frequency. CB/GF hybrid material in PVDF composites has a promising future as a lightweight and cost-effective microwave absorbing materials for both telecommunication and stealth technology.

No abstract

Scale models are used in making engineering measurements. Scale models provide an important means for both estimating the radar cross section (RCS) of targets for which no other method is practical, and for providing independent verification of values found in other ways. For example, if a full-scale target may not be available for measurement or the effect of a design variation on RCS may need to be determined before the final design is chosen, or results of computer modeling of RCS may require verification. This paper deals with the RCS measurements of a scale model of a aircraft at Centro Técnico Aeroespacial.

This paper presents preliminary data from an ongoing study on the radar cross section (RCS) of targets with simple and complex surface geometries (a flat square plate, a 90° dihedral corner reflector and a retired air-to-air missile). Measurements and computer simulations of these metallic targets were carried out at 10 GHz and also when the surfaces of the targets were completely coated with a radar absorbing material (RAM), consisting of flexible sheets of carbonyl iron dispersed in a silicone rubber matrix. Experimental measurements were obtained in an outdoor facility, and computer simulations were performed using a commercial software package. The main objective of this study was to compare results in order to highlight some of the issues related to the determination of the RCS of an actual target. Additionally, a Brazilian research institute has demonstrated the capability to produce and characterize materials related to the main aspects of RCS research, namely, measurement, simulation, and production of RAM.