بررسی تاثیر عوامل ساختاری بر اثربخشی حفاظتی سپرهای الکترومغناطیس دولایه

Introduction: Nowadays, demand for protection against radar radiation using electromagnetic shielding is on the rise.  Double-layer or multilayer shielding were devised in order to improve the single layer electromagnetic shielding properties. In this study, we tried to prepare a new double-layers electromagnetic shield and investigate the effect of structural factors such as thickness, similarity in layers and mixing time on the shielding effectiveness for double-layers shields. Material and Method: This study used the Resin Epoxy EI-403 and Nickel Oxide nanoparticles to prepare single layer shields by casting method (with two different mixing time: 10 and 66 min) in 2, 4 and 6 mm thicknesses and 7 wt% Nickel oxide nanoparticles. Then, in order to prepare double-layers shields, single-layer shields were placed on each other without air space. Scattering parameters were measured by a Vector Network Analyzer (V.N.A) and shielding effectiveness were calculated in X-band radar frequency range. Result: The highest and the lowest averages of shielding effectiveness in single layer shields were 84.14% and 46.05%, respectively. These values were 66.34% and 41.99 %, in double layers electromagnetic shields. The averages of shielding effectiveness values in the double-layers shields (with 10 min in mixing time) in 6, 8 and 10 mm in thickness were 41.99%, 45.45% and 43.25%, respectively. These values in 66 min in mixing time, increased to 54.30%, 62.07% and 66.34%, respectively. Conclusion: In this study, the shielding effectiveness in double-layers were less than single layer electromagnetic shields. Although the increase in mixing time improved the shielding effectiveness of both single and double layer shields, it could not increase the shielding effectiveness in double layer shields in comparison with single layer. Also, the increase in mixing time in double-layer shields showed that shielding effectiveness decreased with increasing thickness in these shields. Also, it was seen that using a similar single-layer shield in the structural of a double-layer shield led to an increase in skin depth and multi reflections .It finally reduced the shielding efficiency in double layer. It is suggested that in the future, other studies be conduct to improve the shielding effectiveness in these electromagnetic shields.